TECHNICAL REPORT - International Nuclear Information ...

TECHNICALREPORT -28

Earthquake mechanisms in NorthernSweden Oct 1987 — Apr 1988

Ragnar Slunga

National Defence Research InstituteStockholm

October 1989

SVENSK KÄRNBRÄNSLEHANTERING ABSWEDISH NUCLEAR FUEL AND WASTE MANAGEMENT CO

BOX 5864 S-102 48 STOCKHOLMTEL 08-665 28 00 TELEX 13108-SKB

EARTHQUAKE MECHANISMS IN NORTHERN SWEDENOCT 1987 - APR 1988

Ragnar SlungaNational Defence Research InstituteStockholm

October 1989

This report concerns a study which was conductedfor SKB. The conclusions and viewpoints presentedin the report are those of the author(s) and do notnecessarily coincide with those of the client.

Information on SKB technical reports from1977-1978 (TR 121), 1979 (TR 79-28), 1980 (TR 80-26),1981 (TR 81-17), 1982 (TR 82-28), 1983 (TR 83-77),1984 (TR 85-01), 1985 (TR 85-20), 1986 (TR 86-31),1987 (TR 87-33) and 1988 (TR 88-32) is availablethrough SKB.

EARTHQUAKE MECHANISMS IN NORTHERN SWEDENOCT 1987 - APR 1988

Ragnar Slunga

Oct 1989

ABSTRACT

A network of six vertical short-period seisnometersdistributed over an area 200*100 square km !... ".orthe: .1Sweden has been in operation since Oct 1987. during t*i»first six months 38 earthquakes within or close to tiienetwork have been located and analysed. The fo :al depthsare in the range 4-30km, the most frequent deaths are 7-9km which is 5km shallower than in southern S w ^ i . T.'<eboundary between the upper and middle crust iS«r smiciLythus seems to be at about 13km in comparison to abcu 18km in southern Sweden. The stresses released by theearthquakes have the horizontal principal compression inor close to the NW-SE quadrant. The most likei :

: recronalstress component has the principal compression in t;»edirection N60W (N120E). If one interprete a .1 LsltKShield earthquake data one gets the same rost l^k-iyorientation for the regional stress component Tharelation between the surface faults and the earthquakefault plane intersections with the surface: is. preliminaryinvestigated. There seems to be a good agreement betweenthe fault plane strikes of the upper crus.al *.".- '.quakesand the surface fault strikes. The dominating ..y*» offault movements is strike-slip at subvertical pJ<:.*cS.This is in agreement with the fault plane solutions forother areas in the Baltic Shield. There is als? a reversefaulting component indicating the possibility ::>at »-hereexists a plate tectonic uplift component in cwedc: , Finallyan alternative view on the Baltic Shield sei* stiri-ci i£>given. It is based on the Baltic Shield er.mhcfuu' e studiesand on the results of geodetic 1 vellinrjs A* iMr>>~nd andNorway. It assumes the earthquakes to be prs?cQ<?-ie;i byaseismic sliding (normally called starve slidir-y ui creep)episodes over large parts of the fault., the *$, <Vvaakesare unstable sliding events at small locked parts(asperities) of the faults. This view means for in^.p^cethat for the geodynamical interpretation ox v in earthquakesthe peak slip is a more relevant parameter thAV A.K seismicmoment. It also leads to estimates of the crustiideformations over southern Sweden of the ortier of ."

TABLE OF CONTENTS

33.13.23.33.43.4.1

3.4.23.53.6

5

6

Appendix 1

SUMMARY

INTRODUCTION

THE DATA ACQUISITION AND EVENT DETECTION METHODS

THE EARTHQUAKESRelation to previous seismicityFocal depthsHorizontal stressesFault plane solutionsThe fault plane solution algorithm - method andsignificanceThe resulting fault plane solutionsFault plane solutions and geophysical lineaments.Seismic moments, static stress drops, fault radii,and fault slips

FAULT MOVEMENTS AND THE BALTIC SHIELD EARTHQUAKES- AN ALTERNATIVE VIEW

REFERENCES

APPENDICES

The earthquake sourceparameters and thefault plane solutions

SUMMARY

The results of the first six months of the operation of asix station seismological network in northern Sweden arepresented. Totally 38 earthquakes have been located andanalysed for source mechanisms. The results are:

- the focal depths are in the range 4-30km, the main peakis around 8km which is 5km more shallow than thesouthern Sweden seismicity

- the stresses released by the earthquake faulting showthat the regional stress in the Baltic shield have aprincipal horizontal compression in the direction N60W

- the estimated dynamic source parameters; the seismicmoments, the static stress drops, and the peak slipsare similar to the results from the other parts of theBaltic Shield area

- the peak slips are typically in the range 0.1-1Omm- the fault plane solutions are for upper crustal events

in agreement with the strikes of the fault lineamentsobserved at the surface

- strike-slip motion at subvertical faults is thedominating type of faulting (transpression)

- there is also a reverse faulting component (compressivecomponent) indicating the possibility that part of theland uplift has a plate tectonic origin.

Based on the earthquake studied and on results ofinterpretations of the geodetic observations in Finland,Norway, and Estonia an alternative view on the Balticshield earthquakes is presented and discussed. It assumesthe earthquakes to be preceeded by aseismic sliding overa fairly large fault surface. The earthquakes occur atfault asperities that have locked a small part of thefault. From a statistical analysis of the intereventdistances the aseismicly sliding fault surface perearthquake is estimated to have lengths of 20-25km. Thisgives the total crustal lateral deformation oversouthwestern Sweden to be about 1 mm per year. The rateof seismic activity in northern Sweden is rather similarto southwestern Sweden which means that the totaldeformation also may be similar. This view on the crustaldeformations and seismic activity in the Baltic Shield areashould be kept in mind as a possibility when planningfuture research on the bedrock deformation processes.

INTRODUCTION

SKB AB (Swedish Nuclear Fuel and Waste Management Co)finances a seismic network in northern Sweden. Thenetwork has been established and is operated by Foa(National defence research institute) in Stockholm.Figure 1 shows the locations of the six stations.During the summermonths in addition mobile seismicstations are operated in the area by the UppsalaUniversity.

Figure 1. The six stations of the network operated by Foawithin this project.

Table 1-1 The

MasugnsbynLansjärvHakkasKalix

station

MUGLJVHAKKLX

Korpilombolo KPMVästmark VMK

coordinates

Latitudenorth67.46266.65566.92566.06766.75565.680

Longitudeeast22.04522.18221.56023.03122.90521.587

This report covers the period 871001-880416

THE DATA ACQUISITION AND EVENT DETECTION METHODS

All stations transmit continuosly frequency modulatedsignals to the central computer at Foa in Stockholm.Permanent telephone lines are used. Gain rangingamplifiers prohibit overloading. The signals and gaininformation are sampled at a rate of 60 Hz. At Stockholmthe analogue signals are bandpass filtered (5-15Hz) andfed into a S/N-detector. When three or four closestations give detections within a time windowcorresponding to the seismic travel time between thestations an event detection is declared and theunfiltered data is saved on digital tape. At least oneminute of data before the detections are included. Inthis way about 20 detected "events" per day are stored ontape. This means that the continous data flow has beenreduced by a factor 0.05. The detection threshold isadjusted continously in order not to run out of magnetictape. It is mainly the wind that determines the actualdetection level. During favourable conditions eventsbelow ML 1 are detected within the network.

The magnetic tapes are then copied into the disc-memory,demultiplexed and submitted to an automatic analysis. Theoutput of this analysis is a list of located seismicevents which are given together with plots of the signals.The list and plot are then checked by the seismologist.Most of the regular mining explosions are in this wayautomaticly located and identified (waveform similaritywith previous explosions) and there is normally no needfor further interactive analysis of most of the events.As almost all local events are explosions this means agreat reduction of the time consuming interactiveanalysis.

In the interactive analysis the seismologist decides whatto save for further source mechanism studies. This meansthat automatic algorithms for fault plane solution, sizedetermination and if needed relative location are run.

The methods for fault plane solution, for estimation ofthe dynamic source parameters, and for relative locationare described by Slunga (1981, 1982). The fault planesolution algorithm is also presented and validated inparagraph 3.5.1 below.

The data for the period (871001-880416) is contained on300 magnetic standard tapes at 800 BPI.

THE EARTHQUAKES

The earthquakes analysed in this report are listed intable 3-1 together with the origin times, locations,depths, and magnitudes.

Table 3-1 The earthquakes analysed1 in this report, valueswithin parenthesis are less reliable.

Date

871011871017871017871220871226871229871230880104880108880110880118880131880202880206880206880207880208880219880225880227880229880304880307880318880322880322880322880329880330880330880401880404880404880404880407880408880410880416

OrigintimeGMT

060123.8040638.8072913.7195226.70829 8.1165643.5032452.3144335.8081423.1104938.1063436.0050212.2111321.0145134.2201544.0192256.2074844.32303 4.81249 9.30637 1.8140826.5215050.5160227.2110014.8040537.3202832.8235836.0060737.5022112.1120635.0013610.5022522.9023316.2174834.8212431.6185110.0194810.6175634.4

Epicenterlat N

66.33666.74264.31665.67567.75967.75465.39165.28067.53767.45467.24766.75667.49167.56067.65166.07167.70366.63166.70164.88564.69065.48066.31265.76767.48667.46365.42667.95265.22067.51867.49367.77967.66266.38767.97467.53966.17566.312

long E

19.89222.87820.89522.50019.55219.56222.94722.52821.57522.34123.72319.19521.88922.21019.36323.51723.35822.78221.99321.03222.73021.53822.13322.82022.26124.28722.60919.39020.03222.41322.19419.62122.11422.60120.78122.66521.90423.738

Focal: depth

(km)

(26.0)8.2

(18.9)9.94.84.8

11.64.5

26.54.0

15.824.86.812.04.96.7

( 6.7)6.9

24.621.64.9

11.78.47.310.55.49.1

(12.8)8.08.99.08.28.618.529.14.3

( 9.6)6.2

Seismicmoment(Nm)

0.15E+120.35E+120.55E+130.19E+120.49E+140.92E+120.14E+120.10E+120.11E+130.40E+120.11E+120.12E+130.17E+120.79E+110.20E+120.37E+110.24E+120.53E+110.12E+110.17E+130.14E+130.44E+110.48E+120.15E+120.80E+110.95E+120.93E+110.79E+120.12E+130.27E+120.11E+120.49E+120.10E+130.38E+110.15E+120.91E+110.47E+110.85E+11

ML

1.21.52.71.33.62.01.21.02.01.61.02.11.20.91.30.61.40.70.12.22.10.61.71.20.92.01.01.92.11.41.01.72.00.61.21.00.70.9

Figure 2 shows their geographical distribution.

Figure 2. The earthquakes that are included in this reportare given by the solid circles. The area wheregeophysical lineaments are mapped by Henkel (1988) isalso marked.

Observational details and results for each earthquakeare given in Appendix 1.

3.1 RELATION TO PREVIOUS SEISMICITY

The time period covered by the present study is about 6months, all six stations in operation for 5 months. It ishowever striking how well the small events of this shorttime interval fits the previous seismicity, see figure.3.

/ r\ t

Figure 3. The solid circles mark the earthquakes of thisstudy. The dotted circles mark previous seismicity fromthe period 1650-1983 as given by the catalogue from theHelsinki University, FENCAT (1987).

Notice that the both the activity west of Kiruna, A, andthe activity around Masugnsbyn, B, are in previouslyactive sites. In the central part, C, the events fill upa previously empty spot.

3.2 FOCAL DEPTHS

The distribution of the focal depths of the earthquakes isof great geophysical interest. The depths are determinedby locating the earthquakes with latitude, longitude,focal depth, and origin time as free parameters. This isa nonlinear inversion problem which is solved iterativelyby minimizing the weighted square sum of the timedifferences between the observed and the theoreticalarrival times of the first P- and S-waves. The uncertaintyof the estimated location is normally estimated bystatistical considerations. The time differences (theresiduals) are typically assumed to be uncorrelated and tohave a normal distribution with zero mean value. The sizeof the uncertainties depends on the station configurationaround the event and on the standard deviation assumed forthe time residuals, in the application within this projectthe first P-wave arrival times have been assumed to have adistance dependent standard deviation going from 0.1s atzero distance to 0.25s at 160km and to 0.63s at 200km. Infigure 4a the typical confidence intervals are shown forevents at different crustal depths. As the depth estimateproblem is nonlinear the confidence limits will beasymmetric in length if both sides (upper and lower) havethe same probability.

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O 5 10 15 20 25 30 35 40Focal depth, km

Figure 4a. The typical 68% confidence intervals for the eventswithin the network. The circle marks the depth around whichthe confidence interval has been computed. The upper andlower part jf the confidence intervals have che sameprobability. As the depth estimate procedure is nonlinearthis causes the confidence intervals to be assymmetric.

The accuracy of the location procedure and the validity ofthe error estimates are most easily checked by locatingevents with known true positions. To check the focal depthdeterminations and the uncertainty estimates I thereforelocated 190 surface events (events with clear short periodsurface waves, Rg) within or close to the network. Someof these events were located to nonzero depths while somehad no optimum deeper than zero depth. If the locationalgorithm is unbiased one would expect 50% of these eventsto be located to depths below the true depth and 50% to belocated to depths above. Figure 4b shows the results ofthis test. It can there be seen that this test gave hardlyany bias at all. Furthermore the distribution of thedistance to the surface in units of estimated standarddeviations for the events given nonzerc depths is smallerthan expected for a normal distribution. This shows thatthe estimated uncertainty is larger than the trueuncertainty. In conclusion the statistical assumptionsabout the standard deviations of the time residuals arenot too optimistic. Note that the fact that there is nobias for these surface events not necessarily means thatthere is no bias for deeper events but it means thatthere are no indications of such a bias.

In the following the depth distribution of the earthquakeswill be estimated. In estimating the relative frequencyboth the nonlinearity and the uncertainty of the focaldetermination procedure have been included. To illustratethe effects of the procedure figure 4c shows both thefrequency of the estimated focal depths for the surfaceevents and the estimated focal depth distribution whenthe uncertainties have been included. The verticaluncertainties of the free depth location procedure arerather large for very shallow events. Full considerationof this means that it only can be stated that the eventsare distributed in the depth range 0-5km.

CD

dCO"OCDCDCJXCD

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Z73

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Standard deviations to surface

Figure 4b. The results of locating 190 surface events (mostlyexplosions, all with clear Rg-waves) with the focal depthas a free parameter. The x-axis gives the resulting focaldepth expressed in terms of the number of standarddeviations to the surface (the true depth). In estimatingthis distance the nonlinearity of the depth determinationhas been included. The y-axis gives the probability ofexceeding the values of the x-axis. The solid curve is thenormal distribution implicitly assumed in the estimate ofdepth errors. It has the 50% value at zero depth. Thedotted curve gives the resulting probabilities for the 190events. We see a small bias, the 50% value (0.5 value) isat 0.04 standard deviations from the surface, this means adepth of 0.6km as the standard deviation at the surface isabout 15km. If the same bias (0.04 s.d.) existed at say10km depth it would correspond to 0.2km. It is howeverpossible that there exist bias for deeper events. What ismore important in the figure is that the dotted curve showsthat the estimated errors (solid curve) are larger than thetrue errors (dotted curve). The difference is about afactor 2. The error estimates are thus not too optimisticbut rather on the conservative side.

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5 IC 15 20 25 3C 35 4G 45roca! dscth, Vi

Figure 4c. To the left is shown the frequencies of theestimated focal depths (free depth location) of 190surface events. To the right the estimated focal depthdistribution is given when the uncertainties of the depthestimates have been included. As the estimateduncertainties are rather conservative it can only bestated that the "surface" events are distributed in thedepth range 0-5km.

The figure above shows that by including the uncertaintyof the depth determination in the estimate of the focaldepth distribution we avoid going further in theconclusions than the data allow.

In figure 4d the estimated focal depth distribution ofthe Norrbotten earthquakes is shown.

- Q'

t-cca. ce:

Figure 4d. The focal depths of the earthquakes. This estimatedrelative frequency has been achieved by considering thenonlinearity and uncertainty of the focal depthsestimates.

It is obvious from figure 4d that the we have at least twodifferent populations, the events at less than some 13 kmdepth, and the events at 13-30 km depth. No events aredeeper than 30-35km. A rather similar type of depthdistribution was found by Slunga (1985) for the southernSweden events. The limits of the two depth intervals arehowever different, see figure 5.

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0 5 10 15 20 25 30 35 40 45 50Focal depth, km

Figure 5. The estimated relative frequencies of the northernSweden earthquakes, solid line, compared to the southernSweden events, dotted line, estimated by Slunga (1985).The northern first (main) peak drops about 5 km shallowerthan the southern first peak.

Slunga (1985) interpreted the two drops in relativefrequencies for the southern Sweden earthquakes as due totemperature effects on quartz (18 km drop) and feldspar(35 km). At higher temperatures they become ductile. Withthis interpretation applied to figure 5 one shouldconclude that the temperature gradient is 30-40% higher-in the upper crust (0-13km) in Norrbotten than insouthwestern Sweden. This is probably not true. Otherpossibilities include differencies in the composition ofthe upper crustal rock and/or differencies in their depthdistribution (a more shallow Conrad discontinuity inNorrbotten). The crust in northern Sweden is severelhundred million years older than in southwestern Swedenand has been eroded several kilometers more, this mayfavour the interpretation of the drop in seismicity at13 or 18 km depths as due to a lithological boundary(the Conrad discontinuity). The lack of seismic activitybelow 30-35km is probably mostly a temperature effect.

The conclusion is that the earthquakes in Norrbottenduring this time period had a more shallow main peak intheir relative frequency of focal depths than theearthquakes of southwestern Sweden studied by Slunga(1985). The midcrustal activity in both areas go down to

30-35km depth.

3.3 HORIZONTAL STRESSES

One of the early important results of t'.e Fua rese. rch onthe Nordic seismic activity was the estin'j.;'j of . uorientation of the regional horizontal s>t>. . °s, F'ur.ja(1981).

I use in the following presentation the conceptsintroduced by Slunga (1981): the azimuth c: pr.:

compression of the horizontal deviator-c stt^sby the earthquake slip and the relativ? s:*o of .hisceviatoric horizontal stress.

A few facts about the results normally ^I-"P.:, by theseismic fault plane solutions:

- the deviatoric stress released by the r!d-i'"iquake slipis in principle uniquely determined

- there are normally two possible fauV piancs gi\rn bythe fault plane solution, one is the c-rue *aul . ulane,the other has no physical meaning

- the rock stresses cannot be direct.'y scn.^.fted fromthe fault plane solution, not even by a .-.••; it' r>nal useof rock failure criteria as most v.r-:hq! akes recurs onpre-existing planes of weakness, see McKenzie (1969)

- strike-slip events on vertical fault planes are muchmore valuable than normal or reverse faulting eventsin the determination of the crustal horizontal stressesas for vertical strike-slip events the horizontal rockstress and the horizontal relaxed stress are in generalcloser to each other, see Slunga (1981). This motivatesthe use of the relative size of the horizontaldeviatoric stress relaxed by the earthquake slip indiscussing the regional horizontal stresses.

The fault plane solution consists of the orientation ofthe principal stress axes: the compressive P-axis, thetensional T-axis, and the intermediate principle axisB often called the null axis. Let P be the unit vectorof the P-axis and T be the unit vector of the T-axis,and let N denote a unit vector in the normal directionof an arbitrary vertical plane. Let also pairs ofvectors within brackets denote scalar products. Thenthe relative normal stress, S, on the plane is

S - (NT)(NT) - (NP)(NP)

with the possible size range -1 to 1. The orientation

of N, for which the largest compression is achieved, isthe direction of the principal horizontal compression,the largest compression is always in the range 0 to -1.The orientation of the largest horizontal tens.on isalways normal to the compression and in the range 0 to 1.The relative size, RS, of the horizontal deviatoricstress is defined as

RS = (S(max)-S(min))/2

and will be in the range zero to one. These are theconcepts introduced by Slunga (1981) in establishingthe regional stress fields from earthquake fault planeplane solutions, see also Slunga, Norrman, and Glans(1984) .

As stated above one cannot accurately estimate thecrustal deviatoric stresses cUrectly from single faultplane solutions as the deviations between the stressesrelaxed by the earthquake slip may deviate quite a lotfrom the orientation of the rock deviatoric stress.However, in the long run the accumulated earthquakestress release must equal the stress generated by thetectonic forces. This can also be expected to have thesame orientation as the regional deviatoric stress.Thus if the stresses relaxed by the earthquakes tendto cluster around any direction, especially for strike-slip events, this direction is close to the correspondingdirection of the crustal deviatoric stress. See furtherSlunga (1981).

Now, after establishing the concepts needed, figure 6shows the direction of the horizontal principlecompression and the relative sizes of the horizontaldeviatoric stress for earthquakes in southern Sweden andDenmark, Slunga (1981, 1982, 1985), Slunga, Norrman,and Glans (1984), Slunga and Nordgren (1988), inFinland, Slunga (1979), Slunga and Ahjos (1986), andfinally in northern Sweden, this study.

S ;-•.". ST, S»ec=i ana Eenir.srit

Figure 6. The direction of the horizontal compression, thatmeans the direction of the principal compression of thehorizontal deviatoric stress: relaxed by the earthquakes,are given by the directions of the lines. The length ofthe lines are proportional to the relative size, RS, ofthe horizontal deviatoric stress. Each line is the verybest fitting fault plane solution of one earthquake.Totally 130 earthquakes are included. If RS equals unitythe length of the line will equal the diameter of thecircle, that means a pure strike-slip event on a verticalfault.

The scatter of the distributions of the compressivedirections for southern Sweden and northern Sweden arequite different. There is a clear clustering of largeRS-events in the direction N20W-N60W for southernSweden. Only two events have directions of compressionswith large RS-values inconsistent with rock stresseshaving principal horizontal compression within thisrange. Thus the southern Sweden data indicates that thehorizontal regional stress of that area has a NW-SEprincipal compression.

in northern Sweden the scatter is very uniform withinabout halx of the circle. If one interpretes thesefault plai.t solutions in terms of a regional stressfield its principal compression must be N60W in order to

avoid contradictions. However the lack of clusteringindicates that the stress is truely inhomageneous. We seethe picture of a complex pattern of fault movements.

If one interpretes all events of the Baltic Shield areatogether looking for the orientation of one regionalstress field giving the lowest number of contradictionsone again comes to N60W as the best fitting direction ofthe principal compression.

Slunga (1981) pointed out that this direction, WNW-NW,of the horizontal principal compression is in agreementwith a number of stress estimates in Europe north ofthe Alps based on a number of different geological andgeophysical methods.

1C

3.4 FAULT PLANE SOLUTIONS

3.4.1 THE FAULT PLANE SOLUTION ALGORITHM - METHOD ANDSIGNIFICANCE

Classical fault plane solution algorithms make use of theobserved first motion direction of the seismic wavesradiated from the source. As for regional recordings ofweak events typcally less than 3-5 clear first motions areobserved this method is of restricted value in such cases.This was the reason to include the amplitudes in the faultplane solution algorithm that was developed at FOA during1980-1982. The method have earlier been described andpublished, Slunga (1981), Slunga (1982). I will howevergive the main principles here.

- The observed signals (for this network the verticalcomponent of the P- and SV-waves) are deconvolved withthe instrumental response and corrected for the Q-damping. The corner frequency and the low frequencyspectral level are estimated from the spectra of thedeconvolved and corrected signal. The Q-model used is

Q = 320 * SQRT(frequency) for P-waves, and

Q = 480 * SQRT(frequency) for S-waves.

- Based on the location of the event the waves enteringthe time window used in the analysis above aredetermined. Body wave geometrical spreading is assumed(1/R, R=total distance) and the response of the freeground surface is determined for each ray. At shortdistances, up to 70km, only the direct waves areconsidered, at larger distances waves reflected from theMoho-discontinuity will be important. For events at lessthan 25km depth an crustal reflector at 25km depth isalso included. The ray amplitudes of the wave reflectedfrom the internal crustal reflector is assumed to be thesame as the direct wave while the amplitude of the rayreflected from the Moho-discontinuity is assumed to havea different distance dependency. At distances less thanthe critical reflection they are smaller than the directwave, around critical reflection up to 1.5 times thedirect wave and for larger distances falling off to thesize of the direct wave.

- The earthquakes have, in the fault plane solutions ofthis report, been treated as pure shear slip events, thatmeans the double couple radiation pattern for P- and S-waves have been used. For each ray direction theradiation factor is determined and multiplied with theray amplitude above (geometrical spreading, free surfaceresponse, etc.) which gives the expected observedspectral amplitude for the ray at the station. This

amplitude corresponds to the fault plane solution usedin computing the radiation factor. All rays enteringthe time window used for the spectral estimate aretreated in this way and the total amplitude is assumedto be given by the third root of the sum of the cubes ofthe individual ray amplitudes. The choice of the cubeinstead of square is due to comparison with full wavetheory computations (synthetic seismograms).

- The differencies between the observed and thetheoretical spectral amplitudes are then computed. Onlyfault plane solutions fitting the amplitude observationsas well as the first motion observations are accepted.Normally a range of acceptable mechanisms are found. Allfault plane solutions are investigated (typically 20 000are tested for each event).

Of special importance in the validation of the use of theamplitudes is the statistical treatment of the amplituderesiduals. I assume that the amplitude residuals (errors)have lognormal distribution, that means the logarithmicerrors follow a normal distribution. I also assume "apriory" that the amplitude residuals at different stationsare statistically independent (uncorrelated) while the P-and S-amplitude residuals at the same stations are highlycorrelated. The reason for this is that there are severalpossible causes to such a correlation: the ray paths arealmost the same, the same instrument is used, the samelocal receiver conditions etc. The following covariancematrix for the P and SV observation at the same stationwas used (e denotes the natural logarithm of the ratio ofobserved and theoretical amplitudes):

e(P) f 1/2 2/3~]e(SV) L 2/3 3/2J

which means a standard deviation factor of 2 for theP-wave amplitude errors and a factor 3.4 for the SV-wave.The correlation coefficient above is slightly less than0.8.

Statistically independent varibles are wanted in thestatistical evaluation of the fit between theoretical andobserved amplitudes. The covariance matrix above gives thefollowing independent residuals at each station: e(P), ande(P)-0.75 e(SV). The variance of the latter is 0.34. Thefit to the observations is then expressed by the size ofthe weighted sum of the squares:

e(P)*e(P)/0.5 + (e(P)-0.75e(SV))*(e(P)-0.75e(SV))/0.34.

These squares are summed over the N observing stations.The sum S has a chi-square distribution with (2N) degreesof freedom. The four free parameters are the seismic momentand the three angles defining the fault plane solution. Theresulting minimum of S, Smin, has then (2N-4) degrees of

freedom.

To get a measure of the statistical significance of theresulting source mechanisms, the following procedure wasadopted. First the sum S was minimized by only varying theseismic moment, while the spatial radiation factors forthe P- and S-waves were both kept constant, each equal toits spatial mean value. This minimum Sref is chi-squaredistributed with (2N-1) degrees of freedom. Afterestablishing this reference sum, we can use an F testwhere the ratio of the two sums, Sref/(2N-1) andSmin/(2N-4), is computed. This gives the significance ofthe resulting source orientation. Note that the conceptin computing Sref, the use of the mean values of theradiation factors, is generally accepted by seismologistsin analysing earthquakes recorded by local/regionalnetworks, most such seismic moments determinations are donein this way. The F-test gives the significance of thefurther step to include the fault plane solution in theanalysis.

The significance value of the F-test gives the probabilitythat similar or better reduction of the sum S would beachieved by pure chance. The distribution of the F-valuesas computed for 274 earthquakes recorded by the Swedishnetworks operated by FOA 1979-1988 is given in figure 7a.The expected cumulative distribution if the double-coupleradiation factor had no physical reality is also shown._One can see that 50% of the events have a significancethat is better (less) than 15%. This result is highlysignificant. Note that if the rays to the stations arewell away from the nodal lines the resulting fault planesolution will be nonsignificant although it may give aperfect fit to the data. The results also show that oneshould take the radiation pattern into consideration whenestimating the seismic moments as more than 25% of theevents show significant improvements (significance betterthan 5%).

c;c;

Figure 7a. The significance of the F-test when the fault planesolution algorithm has been applied to 274 earthquakes.~The x-axis gives the significance level of the resultingradiation pattern (source orientation). The y-axis givesthe distribution functions, the straight line for a randomdistribution, the dots mark the results for the earth-quakes. The deviation from the line is highly significant.

The fit between the theoretical and the observed spectralamplitudes can be expressed in terms of the estimatedstandard deviations for the amplitude residuals. As log-normal distributions are assumed the standard deviationfor the residuals can be expressed by the error factorfor instance for the P-waves, the corresponding errorfactor for the S-waves is above assumed to be 1.7 timeslarger. Figure 7b shows the estimated standard deviationfactor for the P-wave amplitudes as given by the faultplane solutions for the 274 earthquakes.

2 4 6 8 1C 12 14 IG 18Mumber of anpl. Stations, N

Figure 7b. The x-axis shows the number, N, of stations atwhich the P- and S-wave spectral amplitudes have been —observed. The y-axis shows the estimated standarddeviation factor for P-wave amplitudes. For each of the274 earthquakes the circles mark the estimated st. dev.factor based on the value of Smin. The solid line showsthe amplitude criterion used for accepting the mechanisms,it is based on the assumption that the standard deviationfactor is 1.6 (or less) for the P-waves. It can be seenthat all events have fault plane solutions satisfyingthis amplitude criterion.

The value of including the amplitude criterion (asillustrated by the solid curve in figure 7b) into thefault plane solution algorithm is evident from figure 7c.The value of a fault plane solution depends very much onits uniqueness. This can bs expressed as the percentage ofall source orientations that fullfills the fault planesolution criteria. In this case we have two criteria, theobserved clear first motion directions must be inagreement with the theoretical ones, and the amplituderesiduals must be in agreement with the assumption of anerror factor 1.6 for the P-amplitudes. The value of addingthe amplitude criterion to the conventional first motionrequirement is illustrated by figure 7c. Very few eventscan be given welldefined fault plane solutions by use ofonly first motions. This is typical in the study of smallearthquakes by local or regional networks. Only few clearfirst motions are normally observed. It can be seen infigure 7c that the number of events having well defined

fault plane solutions increases drasticly when theamplitude requirement is included.

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Figure 7c. The two figures show the results of applying thefault plane solution algorithm to 274 regionally recordedSwedish earthquakes. To the left an overview, to the ri^jhta blow-up. The uniqueness of the fault plane solutions isexpressed by the percentage of all source orientationsthat fit the criteria. If only first motion directions areused only the events below the horizontal dotted linegive a reasonable degree of uniqueness ( 5 % ) . When theamplitude criterion is added all events to the left of thevertical dashed lines have a uniqueness of 5% or better.This improvement is drastic and without the use ofamplitudes in the fault plane solutions our knowledgeabout the Swedish seismicity had been at a lower level.

So far I have shown that the inclusion of the amplituderadiation pattern (or equivalently the fault planesolution) into the seismic moment estimation algorithmgives significant improvements. It now only remains toshow that the amplitude criterion and the first motionrequirement give the same fault plane solutions. This isbest illustrated by the Lake Vänern earthquake Febr 131981, ML-3.3. For this event 12 clear first motions wereobserved, which gave a highly unique fault plane solutionalready from the first motion directions. Figure 7d showsthat the use of only the amplitudes, without any use thefirst motions, gives the same fault plane solution.

FAULT PLANE ORIENTATIONSGIVEN BY NORMAL VECTORSEQUAL AREA PROJECTION CQ4406391LOWER HEMISPHERE

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Figure 7d. The similarity of the fault plane solutions forthe Febr 13 1981 earthquake in the Lake Vänern area. Thecircles are lower hemisphere equal are projections. Thefault plane orientations are given by the position of thenormals within the circles. To the left all fault planeorientations fitting the 12 clearly observed first motiondirections are given (no use of amplitudes). To the ri-ghtall fault planes fullfilling the amplitude criterion isshown (no use of first motion observations). The bestfitting fault plane solution of the amplitude criterionis within the 1.4% fault plane solutions fitting the12 observed first motion directions.

The fault plane solution algorithm presented and validatedhere has been applied to the northern Sweden earthquakes.The results are given in the following paragraph.

3.4.2 THE RESULTING FAULT PLANE SOLUTIONS

The fault plane solutions can be illustrated andclassified according to the relative sizes of thehorizontal principal stresses computed from the faultplane solution, that means from the deviatoric stressreleased by the earthquake slip. This is illustrated infigure 8.

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Horizontal rel. compressionFigure 8. Each circle marks one earthquake and illustrates

its very best fitting fault plane solution. For a strike-slip earthquake at a vertical fault both the relativesize of the principal horizontal compression and therelative size of the horizontal principal tension willequal unity. The mechanisms pertaining to the othercorners of the square are also given. Note that strike-slip mechanisms are dominating but that there are manyclear reverse faulting earthquakes too. In this figureonly earthquakes having at least one first motiondirection for P-waves, having at least three stationsgiving spectral amplitudes, and having only 10% of thefault plane solutions as acceptable, are included.

in the earlier earthquake studies for southern Sweden andfor Finland Slunga (1981, 1982, 1985), Slunga and Ahjos(1986), and Slunga, Norrman, and Glans (1984), foundstrike slip faulting on subvertical planes to dominate.Even if strike-slip faulting is dominating also innorthern Sweden the many clear reverse faulting events infigure 8 are of great interest. Slunga (1985b) pointedout that in an area of tectonic stress build-up ofreverse faulting type large instabilities will be inducedin the entire brittle crust during deglaciation. Thusreverse faulting movements are expected at the time ofdeglaciation as has been reported by Lagerbäck (1979) innorthern Sweden. The number of reverse faultingearthquakes may be taken as an indication that an excessof horizontal stresses may have been accumulated by thetectonic processes in the area.

Each fault plane solution gives two possible fault planes.Figure 9a shows the dips of these planes for the northernSweden earthquakes. Only earthquakes having less than 10%acceptable fault plane solutions have been included.

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b o

Figure 9a. The dips of planes of the optimum mechanisms fornorthern Sweden earthquakes. The horizontal axis givesthe depth of the earthquake and the vertical axis givesthe deviation from the vertical. For each earthquake twocircles are given, one for each of the two possible faultplanes. Due to the ambiguity one cannot draw very farreaching conclusions from such a diagram but it seemsthe dips of the fault planes may be similar at all depths.

In figure 9b I give the same type of plot as figure 9a butnow for all earthquakes studied by Foa since 1979 andhaving less than 10% acceptable fault plane solutions.The 162 earthquakes of figure 9b are from southern andnorthern Sweden, Denmark, and Finland. See the referencesgiven in the discussion of the regional stress.

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Figure 9b. The two diagrams show dip versus depth forthe rather well defined fault plane solutions of 162earthquakes in Sweden, Finland, and Denmark. The leftdiagram shows the more vertical fault plane for eachearthquake, and to the right the more horizontal ones areshown.

One must remember that figures like figure 9 contain manydifferent possibilities, there may be systematicdifferencies at different depths between the distributionof the real fault plane on the vertical or horizontal one.It is however obvious that subhorizontal fault planes arevery rare but there are some examples within this dataset. The most clear is the event at slightly less than30km depth which is almost purely dip-slip (one faultplane horizontal). This event is from southwestern Sweden,

One can further illustrate the variation of the faultingmechanisms with depth by plotting functions of therelative horizontal principal stresses given by the faultplane solutions and computed as discussed in a previousparagraph. If we define tension as positive andcompression as negative the relative horizontal principalstresses, Shi (principal compression) and Sh2 (principaltension), will have the following ranges: Shi will be -1to 0, Sh2 will be 0 to 1. Then as previously the size ofthe relative horizontal deviatoric stress, RS, isdefined:

RS = ( Sh2 - Shi ) / 2 and be in the range 0 to 1.

Ane er valuable parameter is the sum, Shl+Sh2, whichwill be in the range -1 to 1.

For a strike-slip event on a vertical fault RS=1 and thesum will equal 0. Negative sum values show reversefaulting, crustal compression, and positive values shownormal faulting, crustal extension.

In figure 10 these fault mechanism measures are shownfor the 162 earthquakes.

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Figure 10. The relative size of the horizontal deviatoricstress, RS, is given to the left, and the arithmetic sumof the relative horizontal principal stresses is given tothe right. Each circle denotes the best fitting mechanismof one earthquake. Totally 162 earthquakes are included.

The mean value of the arithmetic sum in figure 10 is-0.06 +/-0.03. Thus there is a weak excess of horizontalcompressive stresses in the earthquake stress release inthe Baltic shield area. In principle this means thatthere may be a tectonic land uplift component.

As pointed out by Slunga, Norrman, and Glans (1984) tieearthquakes close to the Tornquist line has norm-1faulting components. If we divide the Baltic shi Id areawe get the following mean values of the arithmetic sum

of the horizontal relative principal stresses:

latituderange

54-57

57-61

65-69

N

N

N

number ofearthquakes

22

90

34

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.094 H

.097 H

the

r/- 0

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sum

.076

.045

.074

this is theTornquistarea

SW Sweden

N Sweden.

We see that the Tornquist area has an excess ofextension (normal faulting) while both SW Sweden andnorthern Sweden have excesses of compression. Thedominating faulting in all regions (but not for allearthquakes) is strike-slip, that means transpression

28

3.5 FAULT PLANE SOLUTIONS AND GEOPHYSICAL LINEAMENTS

In the studies of southern Sweden earthquakes it wasfound many cases where surface bedrock faults fitted verywell the fault plane solutions. The best example was aML=3.2 event at 9 km depth for which the fault planecould be uniquely estimated from the analysis ofaftershocks, Slunga, Norrman, and Glans (1984). When thisfault plane was extended up to the surface it coincidedwith a dominating some 30 km long surface fault.

It was also found that the strikes of the fault planesolutions normally were the same as the strikes of thedominating surface faults. A good example of this is thechange from N-S-, E-W-faults to NW-SE faults whencrossing the Törnquist line from the north, Slunga,Norrman, and Glans (1984).

As shown in figure 2 nine earthquakes are within the mapof geophysical lineaments produced by Henkel (1988). Iwill in the following compare the fault plane solutionsof these event to the geophysical lineaments on the mapby Henkel. As more events accumulate within the area ofmain interest (the area close to the Lansjärv fault) morecertain conclusions caii be drawn.

The earthquakes are in all pictures marked by circleswith radii showing the location uncertainty. I will showthe intersection'-, of the extended possible fault planeswith the surface. These intersections are defined by thelocation of the earthquake (epicenter and depth) togetherwith the fault plane solution. I will sometimes show allpossible fault plane intersections and sometimes only thevery best fitting possibilities. The lineaments marked bydots in the following maps just happens to have the rightsurface position and the right strike. In order to bepossible actual fault planes to the earthquake underconsideration the dip must also be in agreement. Eachfault outside the epicenter circle of the earthquake musthave a dip towards the circle and in agreement with thefocal depth range and distance from the circle. Only thenthe surface lineament may really mark the true faultplane of the earthquake. Thus if complete dip informationalso was available the uniqueness would be better.

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v A

V A f

Figure 11. The map shows the results for two earthquakesmarked by circles at the epicenters. The radii shows thelocation uncertainty. The dashed lines are the lineamentson the map by Henkel (1988). The solid straight linesshows the surface intersections of the roost likely faultplanes for each earthquake, that means the fault planesolution best fitting the observed amplitudes. Theseevents are further discussed in the text. The dottedparts of the lineaments fit the acceptable fault planesolutions of the event. In order to be a possible faultplane intersection for the earthquake the lineament musthave the right dip in the direction of the center of thecircle.

The earthquake 880225 1249GMT ML=0.1 (!to the left in figure 11, (map 27L):

deep crust,

We see that "all" the NW-SE faults are among the possiblefault plane intersections as marked by the dotted segments.As the event has a focal depth of 22-27 km it is quitepossible that none of the surface lineaments is relevant.However, one should note that one of the three wide zones,the first NE of the epicenter, in the map by Henkel has adip 60 deg SW at a point 15km north of the epicenter. Thedip required by the location and fault plane solution isabout 70 deg SW, which is the dip of the very best fittingfault plane solution marked the solid line NE of theepicenter. This indicates a possibly quite good agreement.The major lineament SW of the epicenter, also marked bydots, is dipping 73 deg SW according to Henkel, and thuscannot be the fault plane. The second major lineament tothe NE has no dip in the map by Henkel, to fit the earth-quake the dip must be 60 deg SW. The smaller faultlineaments are less likely as the event is below the upperseismic layer, 0-13km. in conclusion this deep earthquakeseems to give a good fit to one of the major NW lineamentsdipping SW.

* The earthquake 880219 2303GMT ML-0.4, upper crust,to the right in figure 11, {map 27L):

The epicenter of this event is close to one of the majorlineaments. This lineament is very similar to one of thefault planes of the best fitting mechanism as marked bythe solid lines in the map. The dip from the fault planesolution is very close to vertical. Ten kilometer to thenorth Henkel give the dip 81 deg E for this fault but healso gives the dip 75 deg W at a point about 8 km southof the epicenter. There may thus be a very good fitbetween the earthquake analysis and one of the wide zones.Another quite likely candidate marked by dots in the mapis the lineament east of the epicenter striking NNW. Thedip required, about 60 deg W, is rather common in the mapby Henkel. The fault also has a length, 15 km, well inexcess of the focal depth, probably 4-12km.

;,; v-;^pv^ V

Figure 12a. This figure is similar to figure 11 but for threeother events/ two in the upper crust and one in middlecrust. The circles mark the epicenters of the earthquakes,the radii show the location uncertainty. The solid linesmark in this case all acceptable fault planeintersections with the surface. For reference somelineaments from the map by Henkel (1988) are marked. Seefurther figure 12b where the circles are better visible.

\ 1%

ii

Figure 12b. The lineaments given by Henkel (1988) for thearea of the three events of figure 12a. The dotted linesmark the lineaments having positions and strikes thatfit the fault plane solutions.

* The earthquake 880404 1748GMT, ML-0.6, middle crust,to the right in figure 12a, b, map 26M:

The lineament going through the epicenter circle seems tobe a likely candidate. However, the dip for a point 10kmsouth of the epicenter is 59 deg W according to Henkel(1988). This makes this lineament less likely. Theclosest major lineament does not fit. In conclusion thereremains no definite candidate although both the NW-SE andNNE-SSW directions of the fault plane solutions are wellrepresented by surface lineaments in the area. There isfor instance a lineament NW of the epicenter which, ifextended SE, would fit the event.

* The earthquake 880307 1602GMT, ML=1.7, upper crust,the central event in figure 12a,b, map 26L:

There are no lineaments at all in the close vicinity ofthe epicenter. A check on the topographic map, 26L SO,shows that the surface topography is dominated by NNW-NW striking lineaments. The wide zone NE of the epicenteris among the possible faults. Its dip direction given byHenkel is also in agreement with the fault plane solution,Also this event may thus be a strike-slip event at amajor fault zone. The very best fitting mechanism ishowever normal faulting at E-W or NE-SW faults which arenot seen on the map by Henkel.

* The earthquake 880410 1948GMT, ML=0.7, upper crust,to the left in figure 12a,b, map 26L:

This earthquake has essentially two possible faultstrikes, NNW and ENE. Only the NNW fits the lineaments onthe map by Henkel. Two of the three dotted fits arerather curved and at least one of them has totallydifferent dip. Thus the short segment close to theepicenter seems to be a likely candidate. If it isdipping steeply to the west it may be the fault plane ofthis event. Note however again that the wide zone NE ofthe epicenter is close to fit the fault plane solution.

\

10 km

\ ,

i

Figure 13. The same as figure 11, and 13. The size of thecircle shows the location uncertainty and the solid linesshows the intersections of the extensions of the best .fitting fault planes with the surface. The dotted partsof the lineaments indicate that they do fit acceptablefault planes.

* The earthquake 880207 1923GMT, ML-0.6, upper crust,the event of figure 13, map 26M:

There are four lineaments striking NW-NNW fitting thefault plane solutions. The dips of these lineaments arenot known but in order to fit to this earthquake theymust be dipping NE with dips 40-90 deg depending on thedistance from the epicenter. Note however again that thewide N-S fracture zone passing through the epicenter fitsthe data of this earthquake provided that the zone isdipping steeply which seems to be the case for thesezones.

Figure 14. Similar to the previous figure. These two eventsare just at the southern boundary of the lineament mapby Henkel (1988). The solid lines show the best fittingsource mechanisms for the events. The dots marklineaments that fit acceptable source mechanisms.

* The earthquake 880318 1100GMT, ML-1.2, upper crust,the right event in figure 14, map 25M:

Two main directions are dominating among the acceptablefault planes, NE-SW and NW-SE. Both directions occur inthe area. Even if on of the wider zones, W of theepicenter, has been marked by dots it does not give avery good fit. The NNW-SSE zone just south of theepicenter seems more likely if it continues further north.The dip should be almost vertical for a fit.

* The earthquake 871220 1952GMT, ML=1.3f upp£r crust,the left event in figure 14, map 25M:

The surface intersections of the extensions of the faultplanes proposed by the fault plane solution fit five ofthe lineaments given by Henkel. We have no dip estimatesfor these lineaments. The best fitting fault planeintersections give no fit with lineaments. The planesNE of the epicentre may be fitting the extension of thewide NW-SE zone seen NNW of the epicenter. If this zonecontinues to SE it would very likely be the fault plane.

One should note that if more earthquake mechanisms areavailable in the interpretation more unique conclusionscan hopefully be made for the individual events. This isat least expected if the earthquakes ?re part of aconsistent deformation of the crust as is indicated bythe boi-h this and previous earthquake studies. One canthus expect much more conclusions in the later reportswithin this project.

The conclusions of this very preliminary investigationare:

- the major zones (the wide zones) are in most caseswithin the sets of possible fault planes

- the possibility that the earthquakes primarily occuron the major, wide zones cannot be excluded

- there are events that are likely to have fault planesoutside the set of wide zones in the map by Henkel.

3.6 SEISMIC MOMENTS, STATIC STRESS DROPS, FAULT RADII,AND FAULT SLIPS

The seismic moments focal depths and ranges of staticstress drops and fault slips are given in appendix 1.The values of these parameters are computed from theestimated corner frequencies. This is discussed by Slungaet al (1984) .

In figure 16 the static stress drops, peak slips, andseismic moments are related to the previous seismicity asgiven by Slunga et al (1984), Slunga and Ahjos (1986),and Slunga and Nordgren (1987).

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Figure 16. The static stress drops and the peak slips plottedagainst the seismic moments. The larger circles denotethe northern Sweden earthquakes while the smaller circlesdenote the previous seismicity in southern Sweden,Denmark, and Finland.

The size of the slip at the fault is typically in therange 0.1-3 mm for these small earthquakes. The ML«3.5event has a slip of 8-30 mm.

Figure 17 shows the depths and seismic moments of thenorthern Sweden events. It is clear from figure 17 thatthe detection threshold for the whole Norrbotten area forthe present 6-station network is about ML=1, for thecentral parts (the area of main interest in this project)it is around ML=0.7 during low-noise periods.

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Figure 17. The seismic moments and focal depths of thenorthern Sweden earthquakes analysed in this report

FAULT MOVEMENTS AND THE BALTIC SHIELD -EARTHQUAKES- AN ALTERNATIVE VIEW

In this paragraph I will present some ideas that arequite hypothetical. However, the present knowledge of theseismicity and of the irregularities in land upliftdiscussed below may be interpreted as leading to thehypothetical view below.

First I summarize some statements representing thepresent knowledge of relevance for the interpretation ofthe small Baltic Shield earthquakes:

- mostly strike-slip faulting on subvertical faults, thatmeans mostly horizontal slip

- typically 0.3-10mm peak slip- the size of the stress drop (static stress drop) does

not depend on the depth (for the same size events)- the earthquake mechanisms indicate a very consistent

regional stress field component in agreement withaspects of the plate tectonics

- the estimated fault surfaces are small, diameters lessthan 300 m for most events

- even earthquakes of magnitudes below ML«1 seems to bepart of the same systematic crustal deformations as thelarger earthquakes (up to ML=5 so far studied).

The last point may be quite significant. If one looks atthe Baltic shield seismicity as a relict from previous moresignificant crustal deformations one could expect to finda more scattered deformation picture for the very smallevents. This because they then would be late adjustmentsaround previous larger movements. The remarkableconsistency is much more easily understandable if thesmall events are directly linked to the present largescale tectonic deformations of the crust.

In Finland repeated geodetic levellings have indicatedvertical fault movements up to 30 mm at rates of up tothe order of 1 mm/year, Talvitie (19'?7), Verio (1979,1982a,b), and Kiviniemi (1980). Verio gives the followingstatements:

- vertical relative movements occur correlating with thecrustal faults

- movements take place both in seismicly active andnonactive areas.

One example given by Verio (1982b) is connected to two ofthe earthquakes studied by Slunga and Ahjos (1986). TheLappajärvi area was levelled 1972 and seven years later1979, the earthquakes occurred a couple of months beforethe relevelling. The earthquakes, strike-slip onsubvertical faults, both with the same mechanism, had -

peak slips of 10-30mm (ML=3.8 and 2.7). The verticaldifferential displacements were 10mm, which is magnitudeslarger than this Mo=lE+14 Nm earthquake will give. Itseems likely that considerable aseismic faulting (creep)has taken place between the levellings. This aseismicfaulting seems to have been of the same mechanism and onthe same fault as the earthquakes at the end of theperiod. In order to get the geodeticly observedvertical displacements the whole fault at a length ofabout 20 km must have slipped about 100 mm. This is ofthe same order of size as the estimated seismic peak slipof 30 mm. It thus seems possible to interprete theearthquakes as asperities locked during the aseismicsliding and then suddenly slipping seismicly. This is thesimplest way to interprete the remarkable geodeticobservations.

In a recent study of geodetic levelling data in EstoniaVallner et al (1988) stated that th' area can be dividedin crustal blocks exhibiting different vertical movementsand tilting. If these differential bitjk movements areinterpreted as fault movements and compared to the seismicactivity, (the largest earthquake for 350 years was the1976 earthquake with the reismic moment 3.5E+15 Nm, Slunga(1979)), one finds that the geodetic (aseismic) faultmovement is at least 20000 times more extensive than theseismic fault movements.

In southern Norway both Bakkelid (1986) and Anundsen (1988]found by geodetic measurements aseismic fault movements ofabout 1 mm/year vertically. Anundsen (1988) found also1 mm/year horizontal fault movements.

In conclusion there are several indications fromFennoscandia and the neighbouring countries of extensiveaseismic fault movements of the order of 10000 times moreextensive than the seismicly observed fault movements.

That a fault sliding movement is aseismic means just thatit cannot be detected by seismic measurements. This meansthat it does not produce earthquakes large enough to bedetected. It is well known that significant aseismicfault sliding occurs in the form of stable sliding inmany parts of the world even if it probably is beststudied in California.

The results summarized above suggest the following viewon the Baltic shield faulting:

- most of the fault movements is episodic aseismicsliding (creep, stable slip) along the crustal faults

- the earthquakes are small areas (asperities) thathappen to be locked during the aseismic fault movementsand suddenly break

- the fault area sliding aseismicly before an earthquakeoccurs (if parts of the fault is locked by an asperity)

may be up to more than 10000 times larger than theestimated earthquake fault area

- the most interesting geophysical parameter for thesesmall Baltic shield earthquakes xs then not the seismicmoment but the peak slip as it gives information aboutthe size of the aseismic fault movement.

In conclusion the earthquakes possibly occur when theaseismic slip is locked by asperities which then fail- _The estimated peak slip will then be a lower bound forthe size of the aseismic fault slip preceeding theearthquake.

This view on the Baltic shield earthquakes points out thepossibilty of a dominating role played by the aseismicsliding. The seismic event cnly shows that sliding hasoccurred and gives the fault plane orientation, thedirection of the slip, and a lower bound of the aseismicslip during the sliding event.

The concept of aseismic sliding preceeding the laterasperity failures giving rise to earthquakes is simpleand makes the earthquakes easily understandable. Theproblems are pushed to the understanding of the aseismicsliding, its mechanisms and general behaviour. Thisunderstanding is in fact quite good and numerical modelsfor fault behaviour based on laboratory results of rocksliding have been quite successful (Tse and Rice (1986),Stuart (1988)). These models give both seismic andaseismic fault movements.

in a study of the Californian seismicity Wesson andNicholson (1988) gave the following statements:

- larger earthquakes along faults exhibiting faultcreep tend to occur at the ends of creeping sections

- large earthquakes tend to occur adjacent to previouslarge earthquakes

- the occurrence of any significant earthquakeincreases the intermediate-term probability of futureearthquakes on adjacent fault segments.

All these three statements will be included if oneaccepts the following statement:

- slip (seismic or aseismic) on a fault segment (block)will increase the probability to have slip (earthquakeor creep) on adjacent fault segments (blocks).

This is the basic idea behind the efforts to estimatethe extension of the aseismic fault slip from thespatial distribution of the Swedish earthquakes as doneby Slunga (1988). In this kind of investigation onerequires a sufficient number of accurately located

earthquakes. The idea behind this investigation is asfollows:

- it is likely that after an earthquake there will be anincreased probability to have a following earthquake onthe very same fault close to the border of thepreviously sliding area (seismic or aseismic) as thestress will be increased there (the domino theorydiscussed above).

In the case that all fault sliding is seismic there mustbe expected to exist an increased probability to have thefollowing earthquake very close to the preceeding one,the distance should be of the order twice the radius ofthe fault area of the earthquakes. One thus expects adistance dependance with increased earthquake probabilityat very small distances for the earthquakes following anygiven earthquake. In the case that the earthquakes areasperities on mostly creeping faults one would expect nosuch increased probability at close distances.

One assumption that must be made (due to the short timeperiod for which we have good data) is that the seismicpreparation time (the time between stress concentrationand earthquake) is less than about one year. This seemsquite reasonable as the earthquakes are quite small, inmost cases less than ML=2.

For each earthquake I computed the distance to theclosest later earthquake. This was done for southwesternSweden, 100 earthquakes. In one case no restriction wasput on the closest later event, in the other case Irequired that the later event had to have an acceptablefault plane solution fitting a plane through the hypo-centers of the events and that also the first eventshould have a similar fault plane solution among itsrange of acceptable fault plane solutions. This latercase means that complete consistancy with the basic idea,that the two events are on the same fault plane and dueto a similar fault slip, was required. See figure 18.

0 10 20 30 40 50 60 70Closest later euent; km, 103 ev.

Figure 18. The figure is based on the main earthquakes insouthwestern Sweden, 54-61 deg north, 10-14.5 deg east,totally 100 events during 1980-1984. The x-axis gives the3D-distance to the closest later event, the y-axis givesthe accumulated distribution. The diagram shows the twoobserved distributions, the dotted line with no faultplane restriction, the solid line requiring consistancywith the main idea that the two events have similarsource mechanisms and are on the same fault plane.

in figure 19 the two observed distributions of figure 18is compared to two theoretical laterally uniformdistributions. The depth distribution is assumed to bethe one defined by the actual depth distribution of the100 events involved and is also given in figure 19.One of the theoretical distributions assumes laterallyuniform three-dimensional (3D) distribution of theevents, the other assumes laterally uniform distributionover a plane through the event, that means a laterally

uniform two-dimensional (2D) distribution. The 2D-distribution is what we would expect for the proposedasperity model if the asperities have a laterally uniformdistribution on the fault planes.

We see from figure 19 that at larger distances the upperobserved distribution (no fault plane restrictions) givesa good fit to a three-dimensional distribution up toabout 35 km. For larger closest event distances there isa clear deviation from also the uniform three-dimensionaldistribution (the events are not uniformly distributedover the whole SW Sweden area). For closer distancesthere is an excess of events. From the comparison withthe 2D-distribution we can conclude:

- there is no indication of an increased earthquakeprobability in the close vicinity (less than 7km) of anearthquake (this is the most important conclusion anda very strong support for my proposed model for theearthquake generation)

- there is an increased earthquake probability in thedistance range 9-15km (this may be taken as anindication of a crustal block structure of 9-15kmtypical dimension if the seismic svents are close toblock corners (fault intersections)).

—•CDenCDCD

uede

n60

7C

CO o

CD••3-

O NI

CO

- - oca

i i i i i i

; /Z^f !

- / / ' •

• /

- /

50 BO 700 10 20 3C 40Closest later euent, km, 103 ev.

Figure 19. The two solid lines are the two observeddistributions of figure 18. The dashed line is thetheoretically expected distribution for events having alaterally uniform 3D distribution. The dotted line is

the expected distribution for events having a laterallyuniform 2D (plane) distribution. The depth distributionof these 100 events is given by the diagram to the right.

From fitting the 2D-distribution to the observeddistribution in figure 19 one can estimate the faultlength of aseismic slip per earthquake. If the basicassumptions are reasonable (as they seem to be) theestimated length of the sliding fault segment perearthquake is 23-25km depending upon if the upper orlower observed curve is used. The discrepancy betweenthis value and the typical spacing of the earthquakes(9-15km) can be taken as an indication that for this dataset (ML down to 1.3) not all of the "block segments"sliding caused a detected earthquake.

One consequence implicit in my proposed model is thatthe earthquakes occur on faults having lengths of atleast 9-15km. This is in agreement with the observationsthat the earthquake fault planes in SW Sweden has thesame orientation (mostly N-S and E-w) as the majorfaults in the area.

The consequences on the estimated crustal deformations bythe view presented here can easily be roughly estimated.During the five years of measurements in the southwesternSweden about 20 main (aftershocks and swarms representedby the main event) earthquakes per year occur with a meanpeak slip of 1.3mm. Based on the hypothetical view on theearthquake generation presented here each of theseearthquakes can be taken as an indication of an event ofaseismic fault sliding at least an amount of 1.3mm. Ifthis sliding is assumed to have affected the whole faultat a length of 23 km it will mean that a total faultlength of 460 km moves 1.3 mm per year. Distributed overa fault length of 600 km (sothern Sweden) it means thatthe extreme points of southern Sweden move 1 mm relativeto each other per year. In achieving this result one mustalso rely on the observed consistency of the fault planesolutions of the SW Sweden events.

The real rate of deformation can be quite different fromthis speculative example as it contains many implicitassumptions:

- the estimated peak slips may be biased (they are ratheruncertain in general) and/or the fault slip may oftenbe larger than the seismic slip

- some faults may be sliding without any seismicity atall (for instance the lack of seismic events on theProtogene zone may possibly be due to the mechanicalproperties of the zone).

What is interesting to note is that arguments basedcompletely on the analysis of the microseismicity maylead to estimate of the horizontal crustal deformations

in SW Sweden of the orders of 1 mm per year. This isin remarkable agreement with the statement by Kakkuriat the symposium on neotectonics in Lejondal Sept 1988that the geodetic measurements in Finland indicatesa horizontal crustal deformation with a rate of 1 mm/yearper 10-100km.

Geodetic monitoring may give answers to the manyquestions about the role of the aseismic fault movementsand clarify the real rate of the Baltic shield crustaldeformations. Note however that it will be essential tocontinue the monitoring of the microseismicity asgeodetical measurements seldom can be extensive enough fora unique interpretation, together with seismic monitoringthe interpretation will be much stronger.

I also want to mention that the view on the Baltic shieldseismicity discussed here explains why the very small andby themselves insignificant ML=1 earthquakes show such aconsistent fault mechanism pattern. Within the view givenhere they are seismic manifestations of much moresignificant aseismic fault movements.

Finally, the view on the Baltic shield seismicitypresented here is not the only possible one at the presentstage. It is however in agreement with many aspects of theseismicity and of the geodeticly observed crustalmovements. This makes it one of the main hypotheticalmodels to have in mind in planning further research.

i REFERENCES

Anundsen, K., (1986). Variations in Quaternary (LateWeichselian relative sea-levels in southwest Norway;observations of isostatic/eustatic movements and activefaulting. Paper presented at the Neotectonics Symposium atLejondal Sept 5-6 1988. (Karl Anundsen, Dept. of Geology,Section B, Univ. of Bergen, N-5007 Bergen, Norway).

Bakkelid, S., (1986). The discovery in Norway of a stronglyactive geological fault and some of its practicalconsequences. Proceed, of the 100th General Meeting of theNordic Geodetic Commission, Sept-Oct, Helsinki, pp 237-245.

Båth, M. (1956). An earthquake catalogue for Fennoscandiafor the years 1891-1950. Sveriges Geologiska Undersökning,Avhandlingar och uppsatser, C 545, Stockholm.

Båth, M. (1979). Earthquakes in Sweden 1951-1976. SverigesGeologiska Undersökning, Avhandlingar och uppsatser,C 750, Uppsala.

Ben-Menahem, A., and Singh, S.J. (11,72). Computation ofmodels of elastic dislocations in the earth, in Methodsin Computational Physics, 12, pp. 299-375, Academic Press,New York.

Boatwright, J. (1980). A spectral theory for circularseismic sources; simple estimates of source dimension,dynamic stress drop and radiated seismic energy. Bull.Seism. Soc. Am., 70, pp. 1-27.

Brune, J.N. (1970). Tectonic stress and the spectra ofseismic shear waves from earthquakes. J. Geophys. Res.,75, pp. 4997-5009.

Cook, N.G.W. (1981). Stiff testing machines, stick slipsliding, and the stability of rock deformation. InMechanical Behaviour of Crustal Rocks, GeophysicalMonograph 24, AGU Washington D.C., pp. 93-102.

Eshelby, J.D. (1957). The determination of the elastic fieldof an ellipsoidal inclusion and related problems. Proc.Roy. Soc. London, 241, pp. 276-296.

FENCAT (1987). Fennoscandian seismic event catalogue.Compiled by Institute of Seismology, University ofHelsinki.

Henkel, H., Hult, K., Eriksson, L., and Johansson, L. (1983).Neotectonics in northern Sweden - geophysicalinvestigations. SKBF/KBS Technical report 83-57, SwedishNuclear Fuel and Waste Management Co, Box 5864 10248Stockholm.

Henkel, H. (1988). Tectonic studies in the Lansjärv region.SKB Technical Report 88-07, Stockholm.

Hill, D.P. (1982). Contemporary block tectonics: Californiaand Nevada, J. Geophys. Res., 87, pp. 5433-5450.

Lagerbäck, R. (1979). Neotectonic structures in northernSweden. Geol. Fören. i Stockholm Förh., 100, pp. 263-269.

Lagerbäck, R., Witschard, F. (1983). Neotectonics innorthern Sweden - geological investigations. SKBF TekniskRapport 83-58.

Madariaga, R. (1976). Dynamics of an expanding circularfault. Bull. Seism. Soc. Am., 66, pp. 639-666.

McKenzie, D.P. (1969). The relation between fault plane

48

solutions for earthquakes and the directions of theprincipal stresses, Bull. Seism. Soc. Am., 59, pp 591-601.

Savage, J.C. (1974). Relation between P-wave and S-wavecorner frequencies in the seismic spectrum. Bull. Seism.Soc. Am., 64, pp. 1621-1627.

Seismology 1984 (1985). Annual report from the division ofapplied seismology, Foa 2, 10254 Stockholm.

Silver, P.G. (1983). Retrieval of source-extent parametersand the interpretation of corner frequency, Bull. Seism.Soc. Am... 73, pp. 1499-1511.

Slunga, R.S. (1979). Source mechanism of a Balticearthquake inferred from surface wave recordings, Bull.Seism. Soc. Am., 69, pp. 1931-1964.

Slunga, R.S. (1981a). Earthquake source mechanismdetermination by use of body-wave amplitudes - anapplication to Swedish earthquakes. Bull. Seism. Soc. Am.,71, pp. 25-35.

Slunga, R.S. (1981b). Fault mechanisms of Fennoscandianearthquakes and regional crustal stresses. Geol. För. iStockholm Förhandlingar, 103, pp. 27-31.

Slunga, R. (1981c). Focal mechanisms of earthquakes inScandinavia - A review. Earth evolution sciences, 1, pp.61-65.

Slunga, R.S. (1982). Research on Swedish earthquakes 1980--1981. FOA Report C 20477-Tl.

Slunga, R.S., Norrman, P. and Glans A.-C. (1984a). Balticshield seismicity, the results of a regional network.Geophys. Res. Letters, 11, pp. 1247-1250.

Slunga, R.S., Norrman, P. and Glans A.-C. (1984b).Seismicity of southern Sweden. FOA Report C 20543-T1.

Slunga, R.S. (1985). The seismicity of southern Sweden,1979-1984, final report. Foa report C 20572-T1, April1985, ISSN 0347-3694, Stockholm.

Slunga, R.S. (1985b). Research on bedrock stability, (inSwedish), Foa report C 20578-T1, ISSN 0347-3694.

Slunga, R., and Ahjos, T. (1986). Fault mechanisms ofFinnish earthquakes, crustal stresses and faults.Geophysica, 22 1-2, pp. 1-13.

Slunga, R., and Nordgren, L. (1987). Earthquakemeasurements in southern Sweden Oct 1, 1986 - Mar 31,1987. SKB Technical Report 87-27, Swedish Nuclear Fueland Waste Management Co, Box 5864 10248 Stockholm.

Stuart, W. D. (1988). Forecast model for great earthquakesat the Nankai Trough Subduction Zone. PAGEOPH vol 126, pp619-641.

Talvitie, J. (1977). Seismotectonics of northern Finland andthe Fennoscandian shield. Univ. of Oulu, Dep. ofGeophysics, Contrib. 82.

Tse, S. T., and Rice, J. R. (1986). Crustal earthquakeinstability in relation to the depth variation offrictional slip properties. J. Geophys. Res. 91, pp 9452-9472.

Vallner, L., Sildvee, H., and Torim, A. (1988). Recentcrustal movements in Estonia. Journal of Geodynamics, vol9, pp 215-233.

Verio, A. (1979). Problemet med rörelser i jordskorpan vid

4?

grundavvägning i Finland (Problems with crustal movementsin connection with levellings in Finlans).- Det åttendenordiske geodetmöte, Bind 2, Oslo.

Veriö, A. (1982a). Muhoksen montun muotuilua (Remodelling ofthe Muhos grave). Geologi 2/82, Vammela.

Veriö, A. (1982b). På jakt efter den obekanta mekanismen ilandhöjningen. Nordiskt symposium: Landhöjning och kust-bygdsförändring Luleå 2-4 juni 1982, symposiepublikationvolym 1.

Wahlström, R. (1978). Magnitude scaling of earthquakes inFennoscandia, Seismological Institute, Uppsala University,Report 3-78.

Wesson, R. L., and Nicholson, C. (1988). Intermediate-term,pre-earthquake phenomena in California 1975-1986, andpreliminary forecast of seismicity for the next decade,PAGEOPH, vol 126, pp 407-446-

APPENDIX 1

THE EARTHQUAKE SOURCE PARAMETERS AND FAULT PLANESOLUTIONS

The source parameters of the following earthquakes aregiven:

Date

871011871017871017871220871226871229871230880104880108880110880118880131880202880206880206880207880208880219880225880227880229880304880307880318880322880322880322880329880330880330880401880404880404880404880407880408880410880416

OrigintimeGMT

060123.8040638.8072913.7195226.70829 8.1165643.5032452.3144335.8081423.1104938.1063436.0050212.2111321.0145134.2201544.0192256.2074844.32303 4.81249 9.30637 1.8140826.5215050.5160227.2110014.8040537.3202832.8235836.0060737.5022112.1120635.0013610.5022522.9023316.2174834.8212431.6185110.0194810.6175634.4

Epicenterlat N

66.33666.74264.31665.67567.75967.75465.39165.28067.53767.45467.24766.75667.49167.56067.65166.07167.70366.63166.70164.88564.69065.48066.31265.76767.48667.46365.42667.95265.22067.51867.49367.77967.66266.38767.97467.53966.17566.312

long E

19.89222.87820.89522.50019.55219.56222.94722.52821.57522.34123.72319.19521.88922.21019.36323.51723.35822.78221.99321.03222.73021.53822.13322.82022.26124.28722.60919.39020.03222.41322.19419.62122.11422.60120.78122.66521.90423.738

Focaldepth(km)

(26.0)8.2

(18.9)9.94.84.811.64.526.54.0

15.824.86.812.04.96.7

( 6.7)6.9

24.621.64.9

11.78.47.310.55.49.1

(12.8)8.08.99.08.28.618.529.14.3

( 9.6)6.2

Seismicmoment(Nm)

0.15E+120.35E+120.55E+130.19E+120.49E+140.92E+120.14E+120.10E+120.11E+130.40E+120.11E+120.12E+130.17E+120.79E+110.20E+120.37E+110.24E+120.53E+110.12E+110.17E+130.14E+130.44E+110.48E+120.15E+120.80E+110.95E+120.93E+110.79E+120.12E+130.27E+120.11E+120.49E+120.10E+130.38E+110.15E+120.91E+110.47E+110.85E+11

ML

1.21.52.71.33.62.01.21.02.01.61.02.11.20.91.30.61.40.70.12.22.10.61.71.20.92.01.01.92.11.41.01.72.00.61.21.00.70.9

For each event the following are given:

The arrival time observations and the results of thelocation algorithm.

The input data to the fault plane inversion, first motiondirections and spectral amplitudes for vertical P and S.

The output of the fault plane inversion algorithm: thedynamic source parameters, the very best fitting faultmechanism, and statistical information.

Plots showing all acceptable orientations of the P- andT-axes and of the fault plane normals. These are given inequal area projections of the lower hemisphere. A fourthcircular diagram gives all acceptable relative horizontaldeviatoric stresses. This plot of the horizontaldeviatoric stress is symmetric around the center of thecircle, each point marked in the circle is an endpoint ofa line going through the center to correspondingsymmetrical point. The lines marked by the endpointsgives the orientation and relative size of the horizontaldeviatoric stresses for acceptable solutions. Therelative size is 1 for a diameter (strike slip on avertical fault). The orientation of the line gives theorientation of the principal horizontal compression, theprincipal horizontal tension is normal to the li

The marks in the plots of the P- and T-axes and of thehorizontal deviatoric stresses have the following meaning:

0 well fitting mechanism0 optimum mechanisms.

The marks in the plot of the fault plane normals mean:

R well fitting right-lateral planeL well fitting left-lateral planeb well fitting plane both right- and left-lateral0 best fitting planes.

ORIGIN TIME 87 10 11 06H OlM 23.8S +/- 0.65SLATITUDE 66.336 +/- 0.012 DEG.LONGITUDE 19.8S2 +/- 0.094FOCAL DEPTH 26.0 +/- 24.2 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHHAKHAKVMKVMKKLX

PSPSP

0606060606

0101010101

39.8552.1140.9853.6546.71

-0.030.210.02

-0.170.01

28.01.8

26.11.7

18.9

98.998.9

106.3106.3144.7

47.647.6

132.8132.8100.5

P

P

UP

DOWN

x.l 144.7 100.5

INPUT DATA FOR FAULT PLANE SOLUTION

STN

HAKVMKKLX

DIST.KM99.

107.145.

AZIMUTHDEGREES

.7.8132.9100.7

OMEGA(PZ)METER-SEC

+ 0.16E-09- 0.11E-09

0.14E-09

OMEGA(SZ)METER-SEC

0.34E-090.22E-090.85E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.149E+12 NmLOCAL MAGNITUDE: 1.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)10.1HZ -19.5HZ ( 14.4HZ)

FAULT RADIUS RANGE 35m - 68m ( 47m)

STRESS DROP RANGE 0.20MPa - 1.47MPa ( 0.59MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.4mm - 1.3mm ( 0.7mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 167. 28. degreesT-AXIS 75. 3.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -14 degreesTHE RELATIVE SIZE 0.89

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 124. 72. 22. degreesPLANE B 207. 111. 199.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 214. 18. degreesPLANE B 117. 21.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.6C FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

4.26 % OF ALL MECHANISMS ARE ACCEPTABLE32.8 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS13.0 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 39.7%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.24THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.45FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 44 % LEVEL(F-VALUE: F( 5, 2) - 1. 5*7)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.21S-WAVES 0.22

5 •'•

S ORIENTATIONSEOUAL »PEA PROJECTIONLOWER HErtlSPHERK

OO 0 0

000 0 O

0 0 0 0 0 0 O• O O O 0000<X< 000 Q 00 O00 30 O 00 00 OOOC 00 OO 0 0 0

• i-PO 0 0 O O 00•O OOO O 00 00• 0-0• 0 0

• o

T-AXtS ORIENTATIONS€C'-Mt AFFA PROJECTIONLOWER HCnlSPHERE

0000 O O0 0 O

0O-0000 00 O

O 00

o o*O O OOOO 0 00 9 0 0 '

000 O O 000 O 00 00 •O OOOOOO O O 00 O OOO •

0 0 0 0 0 0 0 0 0 O*0 0 0 00

000 O OO0 0 0O O OOOO O •

:0

0 0 0O"

00000000000000^000«••

—oo-o-o-o——00000 0000 00 00000

oooooOOOOOO

ooooooooooooooooo00

• 0OOOOOO

OOOOOOOOOOOO

000

: OOOOOO: OOOOOOOOOO: OOOCOOOOOOO*: OOOOOOOOOOOOOO •ooooooooooooooo •ooooooooooooo •

OOOOOOOOOOOOO 0 0 •oooooooooo o oooooooo •

OOOOOOO OOOO OOOOOOOooooo o ooooooooooo

OOOO OOOOOOOOOOO 0 Cooooo

-OOOOOOooooo

OOOO

HORISONTAL DEVUTORIC STFESSRELATIVE SIZE AND 1 2 8 4 0 6 0 1 3OP1EHTATICN Or COHPFESSION

OO •OOOOOOOO : •

• OOOOOOO O: •• OOOOO OOO •

• OOOOOC O: •OOO OOOOO : *

OOOOO OOOOC : •OOOOOOOO O DOOOC : •

•OOOOOOOOOOOO OOOOO : •OOOOOOOOOOOOOOOO OOOOO: •

OOOOOOOOOOOOOOOOOO OOOO: •OOOOOOO OOOOOOOOOOOOOOOO •

• 0 0 0 O OOOOOOOOOOOOC O O•O 0 0 0 O OOOOOOOOOO :. 00-000 000-00• : OOOOOOOOOO O 0 0 0 O• 0 0 OOOOOOOOOOOOO O 0 0 0

• OOOOOOOOOOOOOOOO OOOOJOO:0OO0 OOOOOOOOOOOOOOOOOO

• : OOOOO OOOOOOOOOOOOOOOO: OOOOO OOOOOOOOOOOO': OOOOO O OOOOOOOO

• : OOOOO OOOOO• : OOOOO OOO* :0 OOOOOO •

• 000 OOOOO •• :O OOOOOOO •

• : OOOOOOOO: 00

»RRRRPRRSPBRFRRRRRFPRR

LbRPRRPPRLLLbPPFR

L

TAULT PLANE ORIENTATIONSGIVEN BY NORMAL VECTORSEQUAL AREA PROJECTIONLOWER HEHrSPKEFE

F

LLLLLL

LLLLLLLL

•t-LLLLLL•LLLL•LLLL•LLLLLLLbLLL•LLLLL

LLLLLLLLLLLLLLLLLLi.ll

LLLLLLL•LLLL

LLL

1 2 9 4 0 6 0 1 )

LLLFP

PRPPPDFFRCPPRRRRRP

ftPPPFP

•BRFFFRP.R

LLLLLLL

ILILILRRRR LLLLLLL

FBFP LLL LLLLLLLLL:FRFFFPLLLLLLLLLLI.LLLLLLMFFRRbLLLLLLLLLLLLLLLLLL

RRBLLLLLLLLLLLLtLLLLLLL—bLLLLLLLLLLLLLLLLL--- '_RRFFbLLLLLLLLLLLL •»FFFFRbLLLLLLLLLLIP.RFFFF LLLILLLILL •

FRP.FF LLLLLLLLLLL LF FFFJt LLLLDLLLLL

LL LLLL*LLLLL

t-LL

RFRFFRPPP R

ORIGIN TIME 87 10 17 04H 06M 38.8S +/- 0.67SLATITUDE 66.742 +/- 0.025 DEG.LONGITUDE 22.878 +/- 0.113

4.9 KMFOCAL DEPTHHAK no Rg

8.2 +/-

STA ARR. TIMEHAK P 04 06 48.89 -0.04HAK S 04 06 56.59 0.17KLX S 04 07 0.49 -0.01VMK P 04 07 0.41 0.18VMK S 04 07 15.81 -0.47

RES. WEIGHT DIST. AZIMUTH41.5 61.4 289.53.0 61.4 289.52.4 76.1 174.9

20.8 132.6 206.71.2 132.6 206.7

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

HAKVMK

DIST.KM60.

131.

AZIMUTHDEGREES

290.6206.3

OMEGA(PZ)METER-SEC

+ 0.30E-090.12E-09

OMEGA(SZ)METER-SEC

0.11E-080.42E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.353E+12 NmLOCAL MAGNITUDE: 1.5

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)12.5H2 -30.0HZ ( 18.5HZ)

FAULT RADIUS RANGE 23m - 55m ( 37m)

STRESS DROP RANGE 0.92MPa - 12.7lMPa ( 2.98MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 1.6mm - 9.3mm ( 3.5mm)

5 C

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 168. -12. degreesT-AXIS 80. 13.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -10 degreesTHE RELATIVE SIZE 0.95

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 124. 108. 1. degreesPLANE B 214. 91. 162.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 34. 18. degreesPLANE B 124. 1.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 2 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

10.85 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS21.2 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 71.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.07

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.26S-WAVES 0.25

-AXIS ORIENTATIONStOU»L AREA PROJECTION l2?t>0«06«LOWER HEMISPHERE

O O •0 0 1 0 0 : 0 0 0 '

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FAULT PLANE ORIENTATIONSCIVEN SV NORMAL VECTORSEOUAL AREA PROJECTIONLOWER HERISPHERE

L L LLLLLLLLLLLL LLLL

LLLLLLLLLLLLLLLI.LLLLLLLLLLLLLLLLLLLLLL

LLLLLLLLLLLLLLLLLLLLLLLLbbbbLLbLLLLLLL

LLlLbbbbbbbbLLLLLLLL•LLbbbbbbbbLLLLLLLLL•LLbbbbbbbLLLbbbLLL• bbbbbb LLLbbbbLL• RbbbbbL Cbbbbbc.

• bbbbbb bbbbbLR RbbbbLL RbbbbbR-RRbRbbLLRRbbbbRPPRRbPbL LPPbbbRP•PRRRPRLbPRRRbPRRRPRRP. PP.P.RRRRRRftRRRRftPRRRRRPRRRPPRPP•PPRRPR PPPPRRPRPRRPRRR•PRRPPPRR

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bbbbbbbP LbbbbPPPPPP»Lbbbbbbb b t b b t p P P R P fLbbbbbL RbbbbPRRPPP*

LLbbbbLLRPRbbbbbb •LLLLLLLb RRbbbbbLL LLLl.LLLLLLLRRPbbbbbLLLLLLLI.

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E8

ORIGIN Tint 87 1U 17 07H 29M 13.7S +/- 1.39SLATITUDE 64.316 +/- 0.081 DEG.LONGITUDE 20.895 +/- 0.484 ***FOCAL DEPTH 18.9 +/- 11.1 KM

STA ARR. TIME RES.VMK P 07 29 38.22 -0.01VMK S 07 29 56.56 -0.16KLX P 07 29 46.82 -0.11KLX S 07 30 13.20 1.08HAK P 07 29 55.94 -0.01

WEIGHT17.31.02.20.11.5

DIST.155.9155.9219.9219.9293.0

AZIMUTH11.911.926.226.25.7

P

P

P

UP

UP

UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXHAK

DIST.KM

155.219.292.

AZIMUTHDEGREES

11.826.25.7

OMEGA(PZ)METER-SEC

+ 0.24E-08+ 0.11E-08+ 0.16E-08

OMEGA(SZ)METER-SEC

0.48E-08- 0.12E-07

0.65E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.554E+13 NraLOCAL MAGNITUDE: 2.7

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)3.3H2 -30.0HZ ( 4.0HZ)

FAULT RADIUS RANGE 23m - 209m ( 172m)

STRESS DROP RANGE 0.27MPa -199.28MPa ( 0.47MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 1.6mm -128.4mm ( 2.3mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 63. -29. degreesT-AXIS 153. 0.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 63 degreesTHE RELATIVE SIZE 0.88

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -76. 111. 201. degreesPLANE B 202. 70. 22.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 194. 21. degreesPLANE B 292. 20.

STATISTICAL INFORMATION

OF 4 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 4 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.82 % OF ALL MECHANISMS ARE ACCEPTABLE13.4 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS13.6 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 23.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.19THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.36FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 29 % LEVEL(F-VALUE: F( 5, 2) - 2.83)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.22S-WAVES 0.27

-AXIS ORIENTATIONSEQUAL AFEA PROJECTIONLOWES HCMI5PHERE

O 00 OC 0000 00 00 O00 O O 00 O O

•00 O O OO O O0 0 0 0 0 0 0 0 0 0 0 0 '

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T-AXIS ORIENTATIONSECUAL AREA PROJECTION 1 2 9 0 0 7 2 ? !LOWER HCKISPKCRE

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HORIZONTAL 0EVIATORIC STRESSRELATIVE S U E ANDORIENTATION Of COMPRESSION

129001393

rAULT PLANE ORIENTATIONSGIVEN »T NORIWL VECTORSEQUAL AREA PROJECTIONLOWER HtKISPHEPE

0 OOOOO• OOOO O• 0 000 0• 0—OOOOOOOOOO-0-O—• OOOOOOOOOOOOO 000 O• ooooooooooooooooooo•oooooooooooooooooOOOOOOOOOOOOO 00OOOOOOOOOOOOO 0•OOOOOOOOOO 0• 00 000 0

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•

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LLLLLLLLL •LLLLL L

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bPLP bR R PRRRR R R •

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L L L LL LLLL L

LLLL LLOOO LLLLLL LLLLLLLLLLLLLLLLLLLLL

LLU.LLLLLL:IL L LL :

ORIGIN TIME 87 12 20 19H 52M 26.7S +/- 0.33SLATITUDE 65.675 +/- 0.021 DEG.LONGITUDE 22.500 +/- 0.033FOCAL DEPTH 9.9 +/- 3.2 KM

STAVMKVMKKLXKLXLJVLJVKPMKPMHA KHA KMUGMUG

ARR.PSPSPSPSP

sp

s

191919191919191919191919

TIME525252525252525352535253

33.7538.7635.0041.1344.9658.2946.630.3250.217.2658.7822.60

RES.0.00

-0.19-0.03-0.050.200.25

-0.01-0.98-0.06-0.630.310.26

WEIGHT52.74.2

47.53.6

25.21.6

22.71.4

18.71.12.50.1

DIST.42.042.050.150.1

110.4110.4122.0122.0145.8145.8200.6200.6

AZIMUTH271.2271.229.728.7

352.3352.38.48.4

343.6343.6354.4354.4

P UP

P UP

INPUT DATA

STN

VMKKLXLJVKPMHAKMUG

DIST.KM44.51.

112.123.148.202.

FOR FAULT

AZIMUTHDEGREES

273.4 +26.5 +

351.87.7

343.3354.1

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.27E-090.21E-090.16E-090.16E-090.16E-090.22E-09

OMEGA(SZ)METER-SEC

0.10E-080.40E-090.11E-080.72E-090.65E-090.12E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.187E+12 NmLOCAL MAGNITUDE: 1.3

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)8.9Hz -12.6Hz ( 10.7Hz)

FAULT RADIUS RANGE 54m - 77m ( 64m)

STRESS DROP RANGE 0.18MPa - 0.50MPa ( 0.3lMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.4mm - 0.9mm ( 0.6mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS -2. 85. degreesT-AXIS 60. -2.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -30 degreesTHE RELATIVE SIZE 0.50

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 155. 43. 96. degreesPLANE B 146. 133. -84.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 245. 47. degreesPLANE B 56. 43.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

2.97 % OF ALL MECHANISMS ARE ACCEPTABLE20.1 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS14.8 % OF THESE FITTED ALSO THZ AMPLITUDES

THE PART OF WELL FITTING PLANES IS 32.0%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.19THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.24FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 7 % LEVEL(F-VALUE: F(ll, 8) - 2.74)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.30S-WAVES 0.25

-AXIS ORIENTATIONSEQUAL ARC» PROJECTIONLOWER HEm SPHERE

T-AXIS ORIENTATIONSEQUAL AHEA PROJECTIONLOWER HEMISPHERE

O :O 00 00 O00 000 00 000 0 0 0 0 000 0 0 000 0 00 000 00 0 00 0 00 000 0 0 0 0 00 00-0-00 O-O-OO

o oooo

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HORIZONTAL DEVJATOPIC STRESSS I Z E ANCON Or COMPRESSION

OOOCO :OOOO'JOCC :

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oooooocooooooooOOOOGOOOOOOOOO: OOOOOO! OOOOOOOO! OOOOOOOOI OOOOO

PAULT PLANt ORIENTATIONSGIVEN BY NORHAL VECTORSEQUAL AREA PROJECTIONLOWEP HEMSPHERE

1 3 5 ( 1 9 5 2 3

• RPRRRRRRbbL• II PJtbLL

t

LLLL•

LLL LL LLLLLLLLLLLLL-LLLLLbbLbLLLLLL LLbbbbbbLLLLLLLLLOObbbPP

• LLLLLLLbbObbbtR• LLLLLLLbbbbRPR• LLLLLbbbbbF• LLLbbbbRRR• LLLbKbURP

L LRPRR• RPRR• RRRR• RPPP

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P.

RR P •PPR

R R*RR RPPFP

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LLbbSbfct RLbLtbbbtb

bbbLbLbbbLbLL-

LLLRLLLLb RPPPLLLLLbhRRLLLLL RP

LbLLL L •LLLLLL •LLLLLLLLLLLL

ORIGIN TIME 87 12 29 16H 56M 43.5S +/- 0.70SLATITUDE 67.754 +/- 0.032 DEG.LONGITUDE 19.562 +/- 0.092FOCAL DEPTH 4.8 +/- 4.3 KM

STAMUGMUGHAKHAKLJVLJVKPMKPMKLXVMK

ARR.PSPSPspspp

16161616161616161616

TIME57575757575757575757

1.6014.794.15

19.2410.5230.8612.7435.2620.9321.66

RES.0.02

-0.120.00

-0.110.030.19

-0.110.42

-0.02-0.05

WEIGHT25.11.6

21.91.3

16.00.96.40.42.01.9

DIST.110.7110.7126.5126.5166.8166.8182.5182.5242.1248.3

AZIMUTH106.0106.0136.2136.2136.2136.2126.1126.1139.5157.9

P UP

INPUT DATA

STN

MUGHAKLJVKPMKLXVHK

DIST.KM

110.126.166.182.242.248.

FOR FAULT

AZIMUTHDEGREES

105.8 +136.2136.2126.1139.5158.0

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.13E-08

OMEGA(SZ)METER-SEC

0.64E-080.44E-09 + 0.17E-080.74E-090.73E-090.53E-090.37E-09

0.27E-080.22E-080.27E-080.12E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.916E+12 NmLOCAL MAGNITUDE: 2.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)5.0HZ -10.6HZ ( 7.6Hz)

FAULT RADIUS RANGE 65m - 138m ( 90m)

STRESS DROP RANGE 0.15MPa - 1.45MPa ( 0.54MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.7mm - 3.0mm ( 1.6mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 30. -58. degreesT-AXIS 86. 19.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-_AXESTHE AZIMUTH OF COMPRESSION 2 degreesTHE RELATIVE SIZE 0.51

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 210. 147. 221. degreesPLANE B 156. 69. 64.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 120. 57. degreesPLANE B 246. 21.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

19.36 % OF ALL MECHANISMS ARE ACCEPTABLE25.7 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS75.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 88.5%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.20THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.25FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 32 % LEVEL(F-VALUE: F(ll, 8) » 1.41)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.28S-WAVES 0.24

c c

-AXIS OSTENTATIONSEQUAL AREA PROJECTIONLOWE» HEMISPHERE

0 0 00 OO OO O O O •

0 0 0 0 0 0»0 0 0 0 0 0 O"o o o o o o o*O O 00 O O 0 0*O 00 O 00000 O •O O 00 O OOO *

O 00 00 00 O O •O 000 0 0 0 0 '

10 OO O O 00 O •1 00 00 O 00O Of O O 00 O0-0-00-0-00-0

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00 00 O OOO 00 O OO O 00 OO O 000 00 OOOOO •O 00 O 00 O OOO 00 O O •

O O O O 00 O O OOOOOO 0 0 0 •O O O 0 0 O O 0 : 0 O 0 0 O •

0 0 0 0 0 0 0 0 0 0 : 0 0 0 0 0 0 ••O OOOO 0 0 0 0 OOOO O 00 O •

O 0 0 0 0 0 0 : 0 O O O O •0-00 0 0 0 0:0 0 0 »

•0 0 0 0:00 •O 0:0

T-AX1S ORIENTATIONSEQUAL AREA PROJECTIONLOWER HEMISPHERE

0 0 0OOOO OOO 000 0 •

OOOOOOOOOOO OOOOOO 0 OOO 00OOOOOOOOOOOOOO OOO 0 OOOOOOOOOOOOOOOOOOOOOOOO OOO

OOOOOOOOOOOOOOOOOOO:OOOOOOOOOOOOOOOOOOO :OOOOOOOOOOOOOOOOO :oooooooooooooooooo

136316565

0 OOOOOOOOOOOOOOOOOO00 OOOOOOOOO

OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO

0000900000000000 1 00 OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 0 :O OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 0 OOO: OCOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO 0 OOOOOO OO 00 OOOOOOOOOOOOOOOOOOOOOOOO 0000000:0 OOOOOOOOOOOOOOOOOOOOO-000000-O- OOOOOOOOOOOOOOOOOOOOOOO 00 I OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOooooooooooooOOOOOOOO 0OOOOOOO OOOOOOO 0OOO OO00 00

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HORIZONTAL 0EV1AT0RIC STRESSRELATIVE SIZE AND 136316565ORIENTATION Or COrtPRESSION

OOOOOOO 0• OOOOOOOOOOOOOOO

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oooooooooooooooooooooooooo• OOOOOOQOOOOOOOOOOOOOOOOOOOOO

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• 0 0 OOOOOOOOOOOOOOOOOOOOOOO• OOOO OOOOOOOOOOOOOOOOO• OOO00-0-0--OO-00--0-0-0O0O0• OOOOOOOOOOOOOOOOO OOOO• OOOOOOOOOOOOOOOOOOOOOOO 00

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OOOOOOOOOOOOOOOOOOOOOOOOOOOOO •• oooooooooooooooooooooooooooooo *• oooooooooooooooooooooooooooooo •• OOOOOOOOOOOOOOOOOOOOOOOOOOOOO •OOOOOOOOOOOOOOOOOOOOOOOOOOOO •oooooooooooooooooooooooooo •OOOOOOOOOOOOOOOOOOOOO 0 •

oooooooooooooooooo •OOOOOOOOOOOOOOO •

0 OOOOOOO

TAULT PLANE ORIENTATIONSGIVEN BY WRnAL VECTORSEQUAL AREA PROJECTION 136 316565LOWE» HEMISPHERE

LLLLLLLLLLLLLLLLLL •

LLLLLLLLI.LLLLLLL RRPRRRRLLLLLLLLLLLLLLLLLLLLLbRRRtRPRbRFLLLLLi.LLLLLLLLLLLLLLLLRPPPPPRF.RPPP*LLLLLLLLLLLLLLLLLLLLLLbRR RR R b FPR

LLLLLLLLLLLLLLLLLLLLbLbbR R bLbLbfcPPPFLLL LL LLLLLLLLbLLLLbbLLL bbLb bRbRbPbPbR

LLLL L bbbbbLbbbbbbbRRbLL bbbbbbbbbRbRPRL RbLbbbbbbbbbbbRbRbbbLLLbLbLbbbbbRbRP• R RP.bbbbbbbbbbbLbbRbRbLLbLLbbbbbbbbbbP.RR• RRRRRbbbbbbbbbbbbbbRRRLbLLLLLLbbbbbbbbbbbR

RR RRRRRRRRbbbbbbbbbbbbbbRR bLLLLLLLLbbbbbbbbbRRPRRRRRRRRRRRbbbbbbbbbbbbbbRLLLLLLLLLLLbbbbbbbbbRbRRRRRRRRRRRRbbbbbbbbbbbbRbLLLLLLLLLLLLbbbbbbbbbbbERRRRRRRRRRRbbbbbbbbbbbbbLLLLLLLLLLLLbbbbbbbbbbbbRRRRRRRRRRRRKbbbbbbbRbRRbLLLLLLlLLLOLbbbbbbbtbtsbbRRRRRRRRRRRPRbRbPbPbRbbLLLLLLLLLOLObbbbbbbbbbbbRRRRRRORRRRRRbbRbbbRRRLLLLLlLLLLLOObbbbbbfcbObbb*RRRROOORRRbRRbbRRRPbLLLLLLLLLbbOOObbbtbeCbbbLRRRPROORRRRbbRRbbRbLL L R RbbbbbObbtbbbbbBLLRRRRRRRRbRbRbbRRRRLLP.LRRRbbbbbbbObbbbbbbbLLRRRRRbbbbbbbRbbRLL :RbbbbbbbbbbbbbbbLbc*RRbbbbRRRRbbRbL LbPbbbbbbbbbbbbbbbbLLLRbbRbR RRRRL LbbbbbbbbbftbfccbbLLLL

RtlRb P. LlLbLbbLLbtsbBLtsLUlR LLbLbLLbLbLLLLLL

• L LLLLLLLLLLLLLLLLL

ORIGIN TIME 87 12 30 03H 24M 52.3S +/- 0.62SLATITUDE 65.391 +/- 0.034 DEG.LONGITUDE 22.947 +/- 0.052FOCAL DEPTH 11.6 +/- 3.0 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHVMK P 03 25 4.00 -0.02 37.3 70.8 297.8VMK S 03 25 12.76 0.14KLX P 03 25 4.81 0.01KLX S 03 25 13.84 -0.14LJV P 03 25 15.79 0.04KPM S 03 25 34.51 -0.02HAK P 03 25 21.18 -0.10

2.635.42.4

18.81.0

70.875.775.7

145.6151.2

297.82.92.9

346.3359.6

6.4 182.5 340.5

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXLJVKPttHAKMUG

DIST.KM66.72.

141.148.177.230.

AZIMUTHDEGREES

295.65.5

347.00.4

340.9351.0

OMEGA(PZ)METER-SEC

- 0.22E-090.14E-090.27E-090.15E-090.14E-090.20E-09

OMEGA(SZ)METER-SEC

0.24E-090.32E-090.05E-090.11E-080.32E-090.88E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT; 0.144E+12 NmLOCAL MAGNITUDE: 1.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)ll.OHz -17.3HZ ( 14.1HZ)

FAULT RADIUS RANGE 39m - 62m ( 48m)

STRESS DROP RANGE 0.26MPa - l.OOMPa ( 0.54MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.5mm - 1.3mm ( 0.8mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 147. -1. degreesT-AXIS 231. 84.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -33 degreesTHE RELATIVE SIZE 0.51

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE * 51. 135. 99. degreesPLANE B 243. 134. 82.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 321. 45. degreesPLANE B 153. 44.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE ANL1 INCLUDED IN THE FIGURES

3.21 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS6.5 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 37.8%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.31THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.40FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 8 % LEVEL(F-VALUE: F(ll, 8) - 2.69)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.27

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ORIGIN TIME 88 01 04 14H 43M 35.8S +/- 0.59SLATITUDE 65.280 +/- 0.034 DEG.LONGITUDE 22.528 +/- 0.036FOCAL DEPTH 4.5 +/- 3.3 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHVMK P 14 43 46.05 0.03 41.0 62.5 316.1VMK S 14 43 53.49 -0.10 3.0 62.5 316.1KLX P 14 43 50.62 -0.04KLX S 14 44 1.85 0.22LJV P 14 44 0.85 -0.09LJV S 14 44 19.56 0.03KPM P 14 44 2.78 0.15HAK P 14 44 5.99 -0.11

30.22.0

91.091.0

14.514.5

17.5 154.5 354.01.0 154.5 354.0

16.1 165.7 5.86.1 188.9 347.0

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXLJVKPMHAK

DIST.KM63.91.

154.166.189.

AZIMUTHDEGREES

316.114.5

354.05.7

347.0

OMEGA(PZ)METER-SEC

- 0.13E-090.82E-100.90E-100.97E-100.90E-10

OMEGA(SZ)METER-SEC

0.11E-090.19E-090.25E-090.22E-090.15E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.104E+12 NmLOCAL MAGNITUDE: 1.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)13.0HZ -23.2HZ ( 17.6Hz)

FAULT RADIUS RANGE 29m - 53m ( 39m)

STRESS DROP RANGE 0.30MPa - 1.73MPa ( 0.76MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.5mm - 1.7mm ( 1.0mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 164. -1. degreesT-AXIS 254. 16.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -16 degreesTHE RELATIVE SIZE 0.96

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 30. 102. 169. degreesPLANE B -62. 101. 12.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 300. 12. degreesPLANE B 208. 11.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

5.76 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS11.4 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 47.9%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.20THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.27FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 1 % LEVEL(F-VALUE: F( 9, 6) - 6.98)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.29S-WAVES 0.20

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ORIGIN TIME 88 01 08 08H 14M 23.2S +/- 0.41SLATITUDE 67.537 +/- 0.022 DEG.LONGITUDE 21.575 +/- 0.093FOCAL DEPTH 26.5 +/- 3.3 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUG P 08 14 28.58 0.00 69.9 21.8 112.3MUG S 08 14 32.67 0.04 6.3 21.8 112.3HAK P 08 14 34.72 0.01HAK S 08 14 43.32 -0.02LJV P 08 14 39.61 -0.04LJV S 08 14 52.08 0.08VMK P 08 14 54.39 0.16VMK S 08 15 17.79 0.00

38.32.7

68.4 180.668.4 180.6

27.2 101.8 165.11.7 101.8 165.12.4 207.3 179.80.1 207.3 179.8

P UP

P UP

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

HAKLJVVMKMUG

DIST.KM67.

100.205.20.

AZIMUTHDEGREES

181.5165.4180.2108.6

OMEGA(PZ)METER-SEC

+ 0.35E-09- 0.38E-09

0.28E-09+ O.OOE+00

OMEGA(SZ)METER-SEC

0.40E-080.38E-080.33E-080.00E+00

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.111E+13 NmLOCAL MAGNITUDE: 2.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)7.3HZ -14.4H2 ( 10.6HZ)

FAULT RADIUS RANGE 47ra - 94m ( 6 5 m )

STRESS DROP RANGE 0.58MPa - 4.43MPa ( 1.77MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 1.4mm - 5.3mm ( 2.9mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 107. 5. degreesT-AXIS 183. -69.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -74 degreesTHE RELATIVE SIZE 0.55

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -4. 44. 240. degreesPLANE B 215. 53. -65.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 86. 46. degreesPLANE B 305. 37.

STATISTICAL INFORMATION

OF 3 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 3 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

0.35 % OF ALL MECHANISMS ARE ACCEPTABLE3.6 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS9.8 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 6.8%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.24THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.46FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 41 % LEVEL(F-VALUE: F( 5, 2) - 1.79)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.25S-WAVES 0.26

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EF. TIME: 104930 REF.GROUP: 0ORIGIN TIME 88 01 10 10H 49M 3Ö.1S +/- O.23SLATITUDE 67.454 +/- 0.014 DEG.LONGITUDE 22.341 +/- 0.038FOCAL DEPTH 4.0 +/- 4.3 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUG P 10 49 40.30 0.01 80.5 12.7 274.3MUG S 10 49 41.78 -0.15 7.8 12.7 274.3HAK P 10 49 49.35 0.07 38.5 60.1 210.2HAK S 10 49 57.53 0.01 2.7 68.1 210.2KPM P 10 49 51.52 0.00 33.2 81.8 162.3KPM S 10 50 1.14 -0.24 2.2 81.8 162.3LJV S 10 50 3.37 -0.22 2.0 89.6 184.9KLX P 10 50 3.70 -0.05 17.1 157.8 160.6

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKKPMLJVKLX

DIST.KM13.60.81.89.

157.

A7,1MUTHDEGREES

276.1210.3162.218 4..:168.5

OMEGA(PZ)METER-SEC

+ 0.30E-080.13E-090.15E-090.11E-090.26E-09

OMEGA(SZ)METER-SEC

0.82F.-080.32E-090.73E-090.75E-090.68E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.397E+12 NmLOCAL MAGNITUDE: 1.6

^HEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)7 . 0 H Z - 1 2 . 0 H Z ( 9.4HZ)

FAULT FJVDIUS RANGE 57m - 98m ( 7 3m)

STRESS DROP RANGE O.lOMPa - 0.9lMPa ( 0.44MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.6mm - 1.7mm ( 1.

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 141. -41. degreesT-AXIS 80. 30.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -22 degreesTHE RELATIVE SIZE 0.58

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 118. 144. —11 - degreesPLANE B 199. 84. 125.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 28. 54. degreesPLANE B 289. 6.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.00 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS1.9 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 18.1%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.26THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.35FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 13 % LEVEL(F-VALUE: F( 9, 6) - 2.60)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.23

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T-AXIS ORIENTATIONSEOUAL AP.EA PROJECTIONLOWER HCKISPHEP.E

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ORIGIN TIME 88 01 18 06H 34M 36.OS +/- 0.44SLATITUDE 67.247 +/- 0.013 DEG.LONGITUDE 23.723 +/- 0.076FOCAL DEPTH 15.8 +/- 2.5 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHKPM P 06 34 46.92 -0.01KPM S 06 34 55.03 0.04MUG P 06 34 48.60 0.01LJV P 06 34 51.58 -0.02LJV S 06 35 3.17 0.07KLX P 06 34 57.65 0.02

39.62.835.229.11.9

65.665.676.195.095.0

213.4213.4289.1226.5226.5

20.3 135.3 193.4

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

KPMMUGLJVKLX

DIST.KM69.80.99.

138.

AZIMUTHDEGREES

215.8287.3227.7195.1

OMEGA(PZ)METER-SEC0.79E-10

- 0.14E-090.30E-100.11E-09

OMEGA(SZ)METER-SEC

0.15E-090.13E-090.19E-090.14E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.109E+12 NmLOCAL MAGNITUDE: 1.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)9.0Hz -12.7Hz ( 10.9HZ)

FAULT RADIUS RANGE 54m - 76m ( 63m)

STRESS DROP RANGE O.llMPa - 0.30MPa ( 0.19MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.3mm - 0.5mm ( 0.4mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 100. -18. degreesT-AXIS 186. 11.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -82 degreesTHE RELATIVE SIZE 0.93

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -38. 111. 185. degreesPLANE B 234. 85. 21.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 232. 21. degreesPLANE B 324. 5.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 4 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

0.13 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS0.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 3.1%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.46THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.71FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 14 % LEVEL(F-VALUE: F( 7, 4) - 3.17)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.4 3S-WAVES 0.27

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ORIGIN TIME 88 01 31 05H 02M 12.2S +/- 0.53SLATITUDE 66.756 +/- 0.015 DEG.LONGITUDE 19.195 +/" 0.086FOCAL DEPTH 24.8 +/- 4.7 KM

STAHAKHAKLJVLJVMUGMUGVMKVMKKPMKLX

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05050505050505050505

TIME02020202020202020202

29.1141.8333.2549.1335.4653.0137.5656.7337.8941.00

RES.-0.13-0.180.100.240.080.180.000.07

-0.01-0.04

WEIGHT26.31.720.91.318.61.116.61.016.46.1

DIST.105.7105.7131.9131.9146.9146.9161.4161.4163.7188.0

AZIMUTH78.778.793.693.656.256.2137.0137.088.3112.4

P

P

P

PP

DOWN

DOWN

DOWN

DOWNDOWN

INPUT DATA

STN

HAKLJVMUGVMKKPMKLX

DIST.KM105.132.146.162.163.188.

FOR FAULT

AZIMUTHDEGREES

78.9 -93.8 -56.3137.1 -88.5 -112.5 -

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.44E-090.11E-080.11E-080.44E-090.63E-090.47E-09

OMEGA(SZ)METER-SEC

0.13E-080.39E-080.28E-080.12E-080.16E-080.15E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.119E+13 NmLOCAL MAGNITUDE: 2.1

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)ll.OHz -30.0HZ ( 15.9HZ)

FAULT RADIUS RANGE 23ra - 62m ( 43m)

STRESS DROP RANGE 2.1lMPa - 42.87MPa ( 6.38MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 3.3mm - 24.8mm ( 7.0mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 115. -12. degreesT-AXIS 24. -6.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -66 degreesTHE RELATIVE SIZE 0.97

THE TWO POSSIBLE FAULT PLANESSTRIKE OIP SLIP

PLANE A 70. 94. -13. degreesPLANE B 159. 77. 176.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 340. 4. degreesPLANE B 249. 13.

STATISTICAL INFORMATION

OF 5 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 5 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.84 % OF ALL MECHANISMS ARE ACCEPTABLE12.7 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS14.5 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 20.9%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.30THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.38FOR SINGLE P-WAVE OBSERVATIONS

THE DOUELE COUPLE SOLUTION IS SIGNIFICANTAT 17 % LEVEL(F-VALUE: F(ll, 8) - 1.97)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.28S-WAVES 0.23

8 4

-AXIS ORIENTATIONSEQUAL AREA PROJECTIONLOWER HEHI5PHERE

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85

ORIGIN TIME 88 02 02 llH 13M 21.IS +/- 0.37SLATITUDE 67.491 +/" 0.020 DEG.LONGITUDE 21.889 +/- 0.043FOCAL DEPTH 6.8 +/" 2.5 KM

STAMUGMUGHAKHA KKPMKPMLJVLJVVMK

PSP

sp

sp

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TIME131313131313131313

22.7023.9931.6339.4636.2247.2136.7547.9253.35

RES.0.000.06

-0.09-0.12-0.12-0.370.260.070.02

WEIGHT87.89.039.92.9

29.61.9

29.31.92.5

DIST7.57.564.964.993.393.394.294.2202.7

. AZIMUTH115.8115.8192.8192.8151.3151.3172.5172.5183.9

P UP

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

HAKKPMLJVMUG

DIST.KM65.93.94.7.

AZIMUTHDEGREES192.9151.3172.5115.3

OMEGA(PZ)METER-SEC

- 0.19E-090.14E-090.11E-09

+ O.0OE+00

OMEGA(SZ)METER-SEC

0.25E-090.58E-090.55E-09O.OOE+00

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.167E+12 NmLOCAL MAGNITUDE: 1.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)10.8HZ -16.5HZ ( 13.6Hz)

FAULT RADIUS RANGE 41m - 63m ( 50m)

STRESS DROP RANGE 0.28MPa - l.OOMPa ( 0.56MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.6mm - 1.3mm ( 0.9mm)

86

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 44. 5. degreesT-AXIS -31. -71.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 45 degreesTHE RELATIVE SIZE 0.54

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -27. 43. -62. degreesPLANE B 117. 53. 246.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 63. 47. degreesPLANE B 207. 37.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

6.95 % OF ALL MECHANISMS ARE ACCEPTABLE32.8 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS21.2 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 54.0%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.14THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.25FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 15 % LEVEL(F-VALUE: F( 5, 2) - 6.59)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.17S-WAVES 0.24

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PLANE ORIENTATIONSBY NORMAL VECTORSAREA PROJECTIONHEMISPHERE

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• LLLLLLLLLLLL LLL LLL

ORIGIN TIME 88 02 06 14H 51M 34.2S +/- 0.42SLATITUDE 67.560 +/- 0.024 DEG.LONGITUDE 22.210 +/- 0.050FOCAL DEPTH 12.0 +/- 2.0 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUG P 14 51 37.07 0.01 80.1 13.1 213.0MUG S 14 51 39.22 0.03HAK P 14 51 46.68 -0.06HAK S 14 51 56.07 0.06KPM P 14 51 49.64 -0.07KPM S 14 52 1.35 0.20KLX P 14 52 1.63 0.32

7.835.1

2.429.1

1.9

13.1 213.76.4 201.976.4 201.994.8 161.294.8 161.2

6.9 170.6 167.4

P UP

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKKPMLJVKLX

DIST.KM13.76.95.

101.171.

AZIMUTHDEGREES

212.9201.9161.1181.1167.4

OMEGA(PZ)METER-SEC

+ 0.22E-090.52E-10

- 0.87E-100.89E-100.95E-10

OHEGA(SZ)METER-SEC

0.87E-090.14E-090.24E-090.27E-090.23E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.789E+11 NmLOCAL MAGNITUDE: 0.9

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)10.7HZ -16.7H2 ( 13.7H2)

FAULT RADIUS RANGE 41m - 64m ( 50m)

STRESS DROP RANGE 0.13MPa - 0.49MPa ( 0.27MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.3mm - 0.6mm ( 0.4mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 170. -1. degreesT-AXIS 80. 25.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXLSTHE AZIMUTH OF COMPRESSION -10 degreesTHE RELATIVE SIZE 0.91

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 122. 108. 18. degreesPLANE B 218. 107. 161.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 32. 18. degreesPLANE B 128. 17.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

5.22 % OF ALL MECHANISMS ARE ACCEPTABLE27.2 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS19.2 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 46.9%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.19THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.25FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 10 % LEVEL(F-VALUE: F( 9, 6) - 2.84)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.27S-WAVES 0.22

90

-AXIS ORIENTATIONSEQUAL AREA PROJECTIONLOWER HEMISPHERE

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91

ORIGIN TIME 88 02 Ob 20H 15M 44.OS +/- 0.86SLATITUDE 67.651 +/- 0.037 DEG.LONGITUDE 19.363 +/- 0.112FOCAL DEPTH 4.9 +/- 4.5 KM

STAMUGMUGHAKLJVLJVKPMKPMKLX

ARR.PSPPSPSP

2020202020202020

TIME1616161616161616

3.0216.814.35

10.6931.0713.4735.0820.89

RES.0.01

-0.19-0.040.010.430.07

-0.36-0.15

HEIGHT23.91.5

22.216.20.96.30.42.0

DIST.116.4116.4124.9165.0165.0183.2183.2239.3

AZI99.399.3

129.6131.2131.2121.5121.5136.0

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGLJVKPMKLXVMK

DIST.KM116.165.183.240.242.

AZIMUTHDEGREES

99.7131.5121.8136.2155.0

OMEGA(PZ)METER-SEC0.16E-090.25E-090.18E-090.28E-090.85E-10

OMEGA(SZ)METER-SEC

0.10E-080.58E-090.93E-090.62E-090.20E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.202E+12 NmLOCAL MAGNITUDE: 1.3

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.6Hz - 9.3Hz ( 6.7H2)

FAULT RADIUS RANGE 74m - 150m ( 102m)

STRESS DROP RANGE 0.03MPa - 0.22MPa ( 0.08MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.1mm - 0.5nun ( 0.3mm)

92

THE ORIENTATION O" THE RELAXED STRESSAZIMUTH DIP

P-AXIS 49. 5. degreesT-AXIS -35. -47.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 51 degreesTHE RELATIVE SIZE 0.72

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -4. 54. -34. degreesPLANE B 107. 63. 221.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 86. 36. degreesPLANE B 197. 27.

STATISTICAL INFORMATION

OF 0 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 0 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

34.91 % OF ALL MECHANISMS ARE ACCEPTABLE100.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS34.9 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 83.3%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.35THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.48FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 32 % LEVEL(F-VALUE: F( 9, 6) - 1.49)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.18S-WAVES 0.24

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ORIGIN TIME 88 02 07 19H 22M 56.2S +/- 0.42SLATITUDE 66.071 +/- O.013 DEG.LONGITUDE 23.517 +/- 0.071FOCAL DEPTH 6.7 +/- 5.0 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTH

KLX S 19 23P 19 23

2.82 0.01KPM P 19 23 9.52 -0.02KPM S 19 23 19.17 -0.17LJV P 19 23 10.84 0.04VMKVMK

P 19 23 12.33 0.00S 19 23 24.03 -0.15

69.66.333.42.330.928.11.8

22.122.181.281.289.098.498.4

269.2269.2340.5340.5317.7244.6244.6

P

P

DOWN

DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

KLXKPMLJVVMKHAK

DIST.KM22.81.89.98.

129.

AZIMUTHDEGREES

269.5340.8317.9244.5316.5

OMEGA(PZ)METER-SEC

- 0.57E-10- 0.32E-10

0.37E-100.23E-100.42E-10

OMEGA(SZ)METER-SEC

0.54E-090.16E-090.84E-100.98E-100.91E-10

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.368E+11 NmLOCAL MAGNITUDE: 0.6

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)3.4Hz - 6.5HZ ( 4.9Hz)

FAULT RADIUS RANGE 106m - 202m ( 140m)

STRESS DROP RANGE O.OOMPa - O.OlMPa ( O.OlMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.0mm ( 0.0mm)

9f

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 138. -12. degreesT-AXIS 193. 70.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -45 degreesTHE RELATIVE SIZE 0.50

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 28. 144. 119. degreesPLANE B 242. 121. 71.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 298. 54. degreesPLANE B 152. 31.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.98 % OF ALL MECHANISMS ARE ACCEPTABLE19.1 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS10.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 33.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.32THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.43FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 30 % LEVEL(F-VALUE: F( 9, 6) - 1.56)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.21S-WAVES 0.25

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ORIGIN TIME 8» 02 08 07H 48M 44.4S +/- 0.54SLATITUDE 67.703 +/- 0.031 DEG.LONGITUDE 23.358 +/- 0.061FOCAL DEPTH 6.7 +/~ 23.3 KM

WEIGHT DIST. AZIMUTH41.2 62.1 245.03.0 62.1 245.0

25.8 107.6 190.71.6 107.6 190.71.5 116.5 222.6

23.9 116.5 222.621.6 128.0 204.41.3 128.0 204.4

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0707070707070707

. TIME4849494949494949

54.542.391.9614.8717.283.395.33

20.18

RES.-0.030.290.00

-0.05-0.12-0.010.07

-0.45

INPUT DATA

STN

MUGKPMHAKLJVKLXVMK

DIST.KM64.

110.119.130.185.241.

FOR FAULT

AZIMUTHDEGREES

243.8191.0222.3204.4184.9200.0

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.39E-090.88E-100.90E-100.95E-100.20E-090.85E-10

OMEGA(SZ)METER-SEC

0.75E-090.37E-090.33E-090.42E-090.38E-090.22E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.237E+12 NmLOCAL MAGNITUDE: 1.4

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)13.4HZ -30.0HZ ( 19.2Hz)

FAULT RADIUS RANGE 23m - 51m ( 35m)

STRESS DROP RANGE 0.76MPa - 8.52MPa ( 2.23MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 1.3mm - 6.3mm ( 2.6mm)

9S

THE ORIENTATION OP THE RELAXED STRESSAZIMUTH DIP

P-AXIS 166. -18. degreesT-AXIS 82. 16.

THE HORIZONTAL DfcVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -10 degreesTHE RELATIVE SIZE 0.91

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 124. 114. -1. degreesPLANE B 214. 89. 155.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 34. 24. degreesPLANE B 304. 1.

STATISTICAL INFORMATION

OF 0 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 0 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

4.26 % OF ALL MECHANISMS ARE ACCEPTABLE100.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS

4.3 % OF THESE FITTED ALSO THE AMPLITUDESTHE PART OF WELL FITTING PLANES IS 30.0*

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.33THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.42FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 4 % LEVEL(F-VALUE: F(ll, 8) - 3.24)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.25S-WAVE5 0.22

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ORIGIN TINE 88 02 19 23H 03H 4.8S +/- 0.42SLATITUDE 66.631 +/- 0.016 DEG.LONGITUDE 22.782 +/- 0.024FOCAL DEPTH 6.9 +/- 7.0 KN

STA ARR. TIME RES. HEIGHT DIST. AZIMUTHKPN P 23 03 7.52 0.03 78.2 14.6 21.2KPM S 23 03 9.32 -0.21 7.5 14.6 21.2LJV P 23 03 9.41 -0.02 64.3 27.5 275.2LJV S 23 03 13.04 0.13 5.6 27.5 275.2HAK S 23 03 22.71 -0.07 2.9 63.1 301.6KLX S 23 03 23.01 -0.08 2.9 64.2 170.0

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

KPMLJV

DIST.KN14.27.

AZIMUTHDEGREES

23.1273.7

OMEGA(PZ)METER-SEC

+ 0.55E-100.12E-09

OMEGA(SZ)METER-SEC

0.26E-090.26E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.531E+11 NmLOCAL MAGNITUDE: 0.7

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)3.2Hz - 6.4Hz ( 4.7Hz)

FAULT RADIUS RANGE 107m - 215m ( 146m)

STRESS DROP RANGE O.OOMPa - 0.02MPa ( O.OlMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - O.lnun ( 0.0mm)

101

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 150. -12. degreesT-AXIS 63. 14.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -28 degreesTHE RELATIVE SIZE 0.95

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 106. 106. 1. degreesPLANE B 197. 91. 162.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 16. 18. degreesPLANE B 107. 1.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 2 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

3.36 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS6.8 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 42.7%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.06

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.42S-WAVES 0.28

102

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ORIGIN TIME 88 02 25 12H 49M 9.3S +/- 0.41SLATITUDE 66.701 +/- 0.026 DEG.LONGITUDE 21.993 +/- 0.031FOCAL DEPTH 24.6 +/- 2.9 KM

STALJVLJVHAKKPMKPM

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1212121212

TIME4949494949

13.4916.6015.6516.8622.48

RES.0.000.000.000.00

-0.01

WEIGHT85.28.6

60.753.64.3

DIST.9.29.231.540.740.7

AZIMUTH123.5123.5322.980.980.9

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

LJVKPM

DIST.KM18.43.

AZIMUTHDEGREES

145.294.7

OMEGA(PZ)METER-SEC

+ 0.45E--100.22E-10

OMEGA(SZ)METER-SEC

0.83E-100.29E-10

DYNAMIC SOURCE PARAMETEFS

SIZE MEASURESSEISMIC MOMENT: 0.115E+11 NmLOCAL MAGNITUDE: 0.1

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (13Ckm)5.5HZ -10.8HZ ( 8.0HZ)

FAULT RADIUS RANGE 63m - 125m ( 86m)

STRESS DROP RANGE O.OOMPa - 0.02MPa ( O.OlMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.0mm ( 0.0mm)

104

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 70. -18. degreesT-AXIS 5. 53.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND '.'-AXESTHE AZIMUTH OF COMPRESSION 76 degreesTHE RELATIVE SIZE 0.58

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP '

PLANE A 18. 142. 34. degreesPLANE B 136. 111. 123.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 288. 52. degreesPLANE B 46. 21.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 2 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

3.33 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS6.7 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTIi!^ PLANES IS 39.4%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.03

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.30S-WAVES 0.23

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ORIGIN TIME 88 02 27 06H 37M 1.8S +/- 0.81SLATITUDE 64.885 +/- 0.047 DEG.LONGITUDE 21.032 +/- 0.121FOCAL DEPTH 21.6 +/- 4.5 KM

STAVMKVMKKLXKLXLJVLJVKPMHAKHAKMUG

ARR.PSPSPsppsp

06060606060606060606

TIME37373737373737373837

16.8728.0727.1746.3333.0757.0535.3336.181.75

43.56

RES.0.00

-0.060.010.080.110.48

-0.260.18

-0.13-0.13

WEIGHT29.81.916.61.02.50.12.22.10.11.5

DIST.92.692.6

161.4161.4204.4204.4225.8229.1229.1291.5

AZIMUTH16.016.034.234.214.214.221.55.85.88.6

P DOWN

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN DIST. AZIMUTH OMEGA(PZ)KM DEGREES METER-SEC

VMK 92. 16.5 - 0.19E-09KLX 161. 34.5 + 0.58E-09

OMEGA(SZ)METER-SEC

0.18E-080.48E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.171E+13 NraLOCAL MAGNITUDE: 2.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)11.6HZ -22.3HZ ( 15.5Hz)

FAULT RADIUS RANGE 30m - 59m ( 44m)

STRESS DROP RANGE 3.55MPa - 25.2lMPa ( 8.46MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 5.3mm - 19.7mm ( 9.5mm)

7 C ?

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 125. 51. degreesT-AXIS 95. -35.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -13 degreesTHE RELATIVE SIZE 0.29

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 136. 17. 29. degreesPLANE B 198. 98. 255.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 226. 73. degreesPLANE B 108. 8.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 2 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.57 % OF ALL MECHANISMS ARE ACCEPTABLE9.6 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS

16.3 % OF THESE FITTED ALSO THE AMPLITUDESTHE PART OF WELL FITTING PLANES IS 26.9%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.17

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.50S-WAVES 0.22

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109

ORIGIN TIME 88 02 27 06H 37M 1.8S +/- 0.81SLATITUDE 64.885 +/- 0.047 DEG.LONGITUDE 21.032 +/- 0.121FOCAL DEPTH 21.6 +/- 4.5 KM

STAVMKVMKKLXKLXLJVLJVKPMHAKHAKMUG

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ARR.06060606060606060606

TIME37373737373737373837

16.8728.0727.1746.3333.0757.0535.3336.181.75

43.56

RES.0.00

-0.060.010.080.110.48

-0.260.18

-0.13-0.13

WEIGHT29.81.9

16.61.02.50.12.22.10.11.5

DI5T.92.692.6

161.4161.4204.4204.4225.8229.1229.1291.5

AZIMUTH16.016.034.234.214.214.221.55.85.88.6

P DOWN

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN DIST. AZIMUTH OMEGA(PZ)KM DEGREES METER-SEC

VMK 92. 16.5 - 0.19E-09KLX 161. 34.5 + 0.58E-09

OMEGA(SZ)METER-SEC

0.18E-080.48E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.171E+13 NmLOCAL MAGNITUDE: 2.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)11.6HZ -22.3HZ ( 15.5HZ)

FAULT RADIUS RANGE 30ra - 59m ( 44m)

STRESS DROP RANGE 3.55MPa - 25.2lMPa ( 8.46MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 5.3mm - 19.7mm ( 9.5mm)

110

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 125. 51. degreesT-AXIS 95. -35.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -13 degreesTHE RELATIVE SIZE 0.29

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 136. 17. 29. degreesPLANE B 198. 98. 255.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 226. 73. degreesPLANE B 108. 8.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 2 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.57 % OF ALL MECHANISMS ARE ACCEPTABLE9.6 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS16.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 26.9%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.17

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.50S-WAVES 0.22

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OUGIN TIME 88 02 29 14H 08M 2 6 . 5 S + / - 0 .33SLATITUDE 6 4 . 6 9 0 + / - 0 . 0 1 2 DEG.LONGITUDE 2 2 . 7 3 0 + / - 0 . 0 2 7FOCAL DEPTH 4 . 9 + / - 4 . 8 KM

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141414141414141414

. TIME080908080908090909

46.711.09

51.6751.9010.0052.1010.001.382.53

RES.0.06

-0.34-0.040.02

-0.630.07

-0.90-0.03-0.09

WEIGHT22.61.4

17.517.41.0

17.21.02.22.1

DIST.122.9122.9154.5155.6155.6156.5156.5221.0230.8

AZI334.6334.65.1

232.2232.272.272.2353.51.9

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXLJVKPMHAK

DIST.KM

120.151.218.227.252.

AZIMUTHDEGREES

334.25.3

353.52.0

348.4

OMEGA(PZ)METER-SEC

+ 0.82E-090.10E-080.97E-090.90E-090.71E-09

OMEGA(SZ)METER-SEC

0.72E-080.41E-080.30E-080.28E-080.16E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.141E+13 NmLOCAL MAGNITUDE: 2.1

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.9HZ - 8.6HZ ( 6.6Hz)

FAULT RADIUS RANGE 80ra - 140m ( 104m)

STRESS DROP RANGE 0.22MPa - 1.19MPa ( 0.54MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 1.0mm - 3.1mm ( 1.8mm)

113

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 47. 62. degreesT-AXIS 83. -23.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 0 degreesTHE RELATIVE SIZE 0.40

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 199. 25. 125. degreesPLANE B 161. 111. -75.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 289. 65. degreesPLANE B 71. 21.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

31.23 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS63.9 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 97.3%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.20THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.27FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 18 % LEVEL(F-VALUE: F( 9, 6) - 2.14)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.25

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115

ORIGIN TIME 88 03 04 21H 50M 50.5S +/- 0.49S ***LATITUDE 65.480 +/- 0.028 DEG. 22.km from n:o 71 ***LONGITUDE 21.538 +/- 0.048 V Pite} 130213391 Rg ***FOCAL DEPTH 11.7 +/- 1.9 KM ***VKK

STA ARR. TIMEVMK P 21 50 54.62 0.02VMK S 21 50 57.51 -0.14KLX P 21 51 5.98 -0.04KLX S 21 51 17.77 0.31LJV S 21 51 28.67 0.24LJV P 21 51 12.17 -0.02

RES. WEIGHT DIST. AZIMUTH69.2 22.5

22.594.8

1.9 94.81.2 134.2

20.5 134.2

6.2-29.1

5.85.8

45.645.612.012.0

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN DIST.KM

VMK 24.KLX 95.LJV 135.

AZIMUTH OMEGA(PZ)DEGREES METER-SEC

1.9 + 0.18E-0944.5 0.29E-1011.3 0.43E-10

OMEGA(SZ)METER-SEC

0.21E-090.78E-100.16E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.438E+11 NmLOCAL MAGNITUDE: 0.6

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.5Hz -11.9HZ ( 7.7Hz)

FAULT RADIUS RANGE 57m - 153m ( 89m)

STRESS DROP RANGE O.OlMPa - O.lOMPa ( 0.03MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.2mm ( 0.1mm)

116

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 81. 17. degreesT-AXIS 172. 3.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 82 degreesTHE RELATIVE SIZE 0.96

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -54. 80. 166. degreesPLANE B 218. 104. -10.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 36. 10. degreesPLANE B 128. 14.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

7.98 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS16.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 56.4%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.07THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.12FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 3 % LEVEL(F-VALUE: F( 5, 2) - 32.84)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.28

117

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0 0 : •O O O O : •' 0 0 0 0 0 0 0 : O •oo ooo oo oo ooo o o o o o o o o o o o o o o oo*

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• 00 0 0 0 0 0 0 0 0 0 0 0 0 0 O O O O O O O O O O •O O O O O O O O O O O : O O O O O O 0 0 0 00*OO-OOO-OO-OO-O——« - O-OO-OO-OO-O—OO*•O O O 00 O 00 : O 00 00 00 O"O 00 00 00 O : 00 000 00 •

000 00 00 t 00 O 000*00 O O : O O 000 O*

•00 O : O OO OO*O i OO 00 •

T-AJIS ORIENTATIONSEQUAL AREA PROJECTION J06421S05LONER HEMISPHERE

00000* 000OOOOOOOOOO t OOOOOOOOO

OOOOOOOOOO : 0 0 0 0 0 0 0 00 0 : ooooo

•0 : OOOOO00

I 0OOOOO i OOOOOOOOOOOOO t OOOOOOO OOO *

0 0 0 0 0 0 0 0 0 0 0 0 0 OOOOOOOODOOOOOOOOODOO*OOOOOOOOOOOOOOOOOOOOOOOODOODOOOOOOOOOooooooooooooooooooooooooooooooooooo

ooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

oooooooooooooooooorooooooooooooooo

HORIZONTAL DEVIATORIC STRESSRELATIVE SIZE ANDORIENTATION Or CORFRESSION

OOOOOO Ooooooooooooo•oooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo• OOOOOOOOOOOOOOOOOOOooooooooooooooooooo•OOOOOOOOOO-OOOOOOOOoooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo0000 OOOOOOOOOOO

• 0 00 0

0 00 0 •OOOOOOOOOOO OOOO

oooooooooooooooooooooooooooooooooooo

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-oooooooo-oooooooooo*ooooooooooooooooooo

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OOOOOOOOOOOOOO'oooooooooooo

0 OOOOOO

TAULT PLANE ORIENTATIONSGIVEN IY NORMAL VECTORSEOUAL AREA PROJECTION J06421505LOWER HEMISPHERE

RR •MtRRRItFRR t L LL

RRRRRRRbRbbbbbbbLLLLLLLLLLLItRRRRRRbbbbbbbbbbbbbbbbbLLLLLLL

• »RRRbbbbbbbbbbbbbbbDbbbbbLlLOLLLLI I ' ItRbbbbbbbbbbbbbbbbbbbbbbbbbLLlLLLL

RRR bbbbLbbbLLLRLUtLLRLbbbbLLLLbLLLLLL*RKRRF bbbLLbL L : R LLLLLLLLLL

RRHRFF LL : LLLLLLLLRRRRR : LLLLL•RRRR : LLLL• : LLL

• : LL

•L LLL L : RLLLLLLLLLLLLLLLL LL LL LLbAbRRRRRRFR RFRRLLLLLIXLLLLLLLLLLLLbbbbbbbftbbbRRRRRRRRRR •ILLLlLlLLLLLLLLLLLbbLbbbbbRbbbRRRRFRRRRRRR •LLLLLLLLLLLLLLLLLLbbbbbbbbbbbRRRRFRRRRRRFRFFF•LLLLLLLLLLLLLLLLLLLLbbKRRRRFRRFRRRRRPRFFFFR*LLLLLLLLLLLLLLLLLLLLLlKMRRRRPPRRRRRPRPRPPRLLLLLLLLLLLLLLLLLL : MRRRRKRRRRRRRRORRK

LLLLLLLLLLLLLLLL :*III>RRRRIIRRR RRR RRLLLLLLLLLLLLL

LLLLLLLLLLLLLLL L

L

•RKRRRRRRRft• MftltRRRRRRR*RRRRRRRRRRRRRRFFRII

118

ORIGIN TIME 88 03 07 16H 02M 27.2S +/- 0.10SLATITUDE 66.313 +/- 0.004 DEG.LONGITUDE 22.134 +/- 0.019FOCAL DEPTH 8.1 +/- 6.0 KM

STALJVLJVKLXKLXKPMKPMHAKHAKVMKVMKMUGMUG

ARR.PSPSPSPSPSPS

161616161616161616161616

TIME020202020202020202020203

33.5838.2935.3740.8837.0144.0439.1547.9739.4348.1848.223.37

RES.0.030.030.10

-0.36-0.08-0.350.00

-0.01-0.03-0.350.08

-0.20

WEIGHT55.44.5

48.23.7

42.13.1

36.52.535.72.5

21.51.3

DIST.38.238.248.948.960.260.272.972.974.974.9128.4128.4

AZIMUTH2.22.2

123.7123.734.434.4339.8339.8199.6199.6358.3358.3

P UP

P UP

INPUT DATA

STN DIST.

LJVKLXKPMHAKVMKMUG

KM39.49.61.73.75.129.

FOR FAULT

AZIMUTHDEGREES

2.4 +123.334.4 +

340.0199.6358.4

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.38E-090.35E-090.26E-090.27E-090.23E-090.68E-09

OMEGA(SZ)METER-SEC

0.24E-080.25E-080.84E-090.12E-080.99E-090.24E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.349E+12 NmLOCAL MAGNITUDE: 1.5

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)2.6Hz - S.lHz ( 4.8Hz)

FAULT RADIUS RANGE 85m - 265m ( 143m)

STRESS DROP RANGE 0.008MPa - 0.247MPa ( 0.05lMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.1mm - 0.7mm ( 0.2mm)

119

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 121. 63. degreesT-AXIS 165. -20.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 82 degreesTHE RELATIVE SIZE 0.45

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -77. 29. 128. degreesPLANE B 241. 113. -71.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 13. 61. degreesPLANE B 151. 23.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

0.83 % OF ALL MECHANISMS ARE ACCEPTABLE33.7 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS2.4 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 21.1%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.27THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.34FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS NOT SIGNIFICANTNOT EVEN AT 50 % LEVEL(F-VALUE: F(ll, 8) - 0.80)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.26S-WAVES 0.35

120

- A I I S ORIENTATIONSEOUAL AREA PROJECTIONLOWER KEHISPKCRE

T - A X I 3 ORIENTATIONSEQUAL AREA PROJECTIONLONE* HEMISPHERE

• O• OOOOOOO• 000000

0 000000 OOOOOOO0- OOOOOOPOO-• 000000000

J067U02J

-.. _ 9 9 ? 91 OOOOOO 00000000 *

oooooooooooooooooooooooooooooooooooooooooooooo oooo ooooooo

00000

oooooooooooo oooooo00000 OOOOOO OOOOOOOOOOOOOO 00000000

OOOOOOOOOOOOOOOOOOO OOOOOOO*ooooooooooo

00tOOOOO

OOOOOOO0<

HORIZONTAL DEVIATORIC STRESSRELATIVE SIZE ANDORIENTATTON Of COMPRESSION

J06716023

FAULT PLANE ORIENTATIONSGIVEN BY NORMAL VECTORSEOUAL AREA PROJECTIONLONER KEHISPRERE

J06716023

• 000• 000000000•oooooooooooooooo•oooooooooooooooo•oooooooooooooooo—• oooooooo• oooooooo• 0000

0000 'oooooooo •oooooooo •

—oooooooooooooooo»oooooooooooooooo»oooooooooooooooo»

000000000 •000 •

00

RRRRRP.RRR : RRRRRRRRRR ! RR

RRRRR ! R• RRRR :

RRRR :RRRRRRRR : LLL

RRRRRRRbbLLLLLLMtRRRbbbOOOLLL

RRbbbbLLLL:LL

LLLLLLLLLL

LLLLLLLLLLLLL

• LLLLL•LLLLLLLL

LLLLLLLLLLLLLL

LLLLLLLLLL

LLLL

: RRP.RRRIIIIRRRLULDRRHRRItRROOOORRRKRRR

ILLbbbbbbbbROOOOORRRRRRRLbbbbbbbRRRRRRRRRIHR

: RR

121

ORIGIN TIME 88 Oi 18 11H OOM 14.7S +/- 0.32SLATITUDE 65.767 +/- 0.018 DEG.LONGITUDE 22.820 +/- 0.044FOCAL DEPTH 7.3 +/- 3.3 KM

STAKLXKLXVHKVMKLJVLJVKPMKPMHAKHAKMUG

ARR.P 11S 11P 11S 11P 11S 11P 11S 11P 11S 11S 11

TIME00 20.00 24.00 24.00 31.00 31.00 44.00 32,00 45,00 37,00 54,01 8,

RES.62 0.0482 -0.0720 -0.0212 -0833362 -0.1926 -080 0.0460 -0.1247 0.00

WEIGHT DIST,57.9 34.94.8 34.9

.080.160.21.19.84

43.53.2

57.57.

26.8 103.4103.110.

1.725.21.6 110.4

19.4 141.11.1 141.10.3 192.4

AZIMUTH15.915.9

260.9260.9343.8343.81.91.9

337.0337.0350.1

P UP

P DOWN

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

KLXVMKLJVKPMHAK

DIST.KM35.58.

103.110.141.

AZIMUTHDEGREES

16.0260.5343.71.9

336.9

OMEGA(PZ)METER-SEC

+ 0.37E-09- 0.13E-09

0.23E-09+ 0.19E-09

0.18E-09

OMEGA(SZ)METER-SEC

0.66E-090.77E-090.50E-090.74E-090.43E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.147E+12 NraLOCAL MAGNITUDE: 1.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)2.9HZ - 6.9HZ ( 4.8HZ)

FAULT RADIUS RANGE 100m - 237m ( 143m)

STRESS DROP RANGE O.OOMPa - 0.06MPa ( 0.02MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.2mm ( 0.1mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 95. 45. degreesT-AXIS 175. -10.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 88 degreesTHE RELATIVE SIZE 0.72

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -56. 51. 151. degreesPLANE B 233. 112. -43.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 34. 39. degreesPLANE B 143. 22.

STATifTICAL INFORMATION

OF 3 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 3 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

2.72 % OF ALL MECHANISMS ARE ACCEPTABLE24.3 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS11.2 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 34.2%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.19THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.25FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 6 % LEVEL(F-VALUE: F( 9, 6) = 3.75)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUM

P-WAVES 0.26S-WAVES 0.25

123

-AXIS ORIENTATIONSEOUAL AREA PROJECTIONLOME» NENISPHERE

•00 00 0 0 0> 0 00

0 00 000 O0 0

00 0 00 000 0 0

--000-O0-OO-O • ' —0 0 00 0 0000 OO 000

T-AZIS ORIENTATIONSCOUAL MEA rROJECTION J07I1LOWER KEKISrHERE

0000000000OOOOOOOOOODOOOOOO 00

•oooooooooooooooooooo

* 000000 00• 00

0 000 00 00 000 00 O 0 000 0 0 01-00-00-00-0-0 00 00 00 000 0 00 0000 0 00 0 00 00 0 0

000*

0*0000 0000 O O

000000 O 0000000

ooooooooooooooooO 00 000 OOOOO 00

000000 000•00000 000000000 00

000000 O

HORISONTAL DEVIATOF-IC STRESSRELATIVE SIZE ANDORIENTATION OF COPIPRESSION

• OOOOO• OOOOO• 000000• oooooooooo•0000000000000•00000000000000•oooooooooooooo"OOOOOOOOOOOOO--•00000000000•00000000000•oooooooooo•oooooooooo• 0000000

J07«lI002

rAULT PLANE ORIENTATIONSGIVEN BY NORMAL VECTORSEQUAL AREA PROJECTIONLONER HEMISPHERE

0000000 *oooooooooo»OOOOOOOOOO'00000000000»00000000000»

—OOOQOOOOOOOOO'oooooooooooooo»oooooooooooooo»ooooooooooooo»

oooooooooo •000000 •OOOOO •

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R»RR :•RRRRR :

RRRR 1•RRRRM R

• RJtRRRRRRR• RRRRRRRRRRRR

RRRRRRFRRBRRRR 1•RRRRP.RR R•

••

•*

• LLLLLLLL LLLLL• LLLLLLL LLLLLLLLL

• L L LLLLLLLLLLL• LLLLLLLL

• :* ;

• LL LI LL LLL L•LLLLLLLLLLLLLLLL

LLLILLLLLLLLLLLLLLLLLLLLL

• LL L•

•

»[ •! •r LLLLLLLL •rLLLLLLLLLLLLLL •:LLLLLILILLLILLLLLL:LLLLLLLLLLLLLLL L»LLLLLLLLOOLOLLLLL L L»: LLLLLLLLLLLLLL LL •! tLLLLLLLLL LL •: LLL LL L •: •

:

• *: RRRRRIIIIRRRRIIFR •: RRRRRRDIIRRRIIRPItlt*: RURKPPPPRRRPRR-I RRRRRItPRRRRliP »I RRRRROORORRRR*: RRRRPRQRIIIIRRR'i RRRRRRRRRKR»1 RRRRRRRR: KRRRR!

124

ORIGIN TIME 88 03 22 04H 05M 37.3S +/- 0.31SLATITUDE 67.486 +/- 0.018 DEG.LONGITUDE 22.261 +/- 0.043FOCAL DEPTH 10.5 +/- 2.3 KM

STAMUGMUGHARHAKKPMKPMLJVLJVKLX

ARRPSPSPSPsp

040404040404040404

. TIME050505050506050606

39.5941.2548.7456.9851.352.08

52.613.623.17

RES.0.01

-0.05-0.01-0.22-0.070.240.11

-0.09-0.05

WEIGHT84.68.5

37.82.731.72.1

29.71.9

16.6

DIST9.79.7

69.769.786.386.393.093.0

162.1

. AZIMUTH253.8253.8206.2206.2160.8160.8182.6182.6167.6

INPUT DATA

STN

HAKKPMLJVKLXVMKMUG

DIST.KM69.86.92.

161.203.9.

FOR FAULT

AZIMUTHDEGREES

206.4160.6182.6167.5188.8257.7

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.47E-100.82E-100.59E-100.15E-090.63E-10

- 0.00E+00

OMEGA(SZ)METER-SEC

0.15E-090.21E-090.23E-090.41E-090.17E-090.00E+00

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.799E+11 NmLOCAL MAGNITUDE: 0.9

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)9.3HZ -13.2HZ ( 11.4HZ)

FAULT RADIUS RANGE 52m - 74m ( 60m)

STRESS DROP RANGE 0.09MPa - 0.24MPa ( 0.16MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.2mm - 0.4mm ( 0.3mm)

125

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 79. -23. degreesT-AXIS -9. 4.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 79 degreesTHE RELATIVE SIZE 0.92

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 37. 109. -15. degreesPLANE B 122. 76. 160.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 307. 19. degreesPLANE B 212. 14.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

13.27 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS26.9 % OF THESE FITTfcD ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 74.7%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.23THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.30FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 22 % LEVEL(F-VALUE: F( 9, 6) - 1.88)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.18S-WAVES 0.19

-AXIS ORIENTATIONSEOUAL AIICA MOJCCTIOKL O N »

O 0 0 0:0 •0* 0 00000 00 •

0 0000 0 0 •oo oo O;o o o o o o •

0 0 O O 000 0 0 0 0 0 0 0 0 *• o I O O O O O O O O O ** 1 O OO O OOOOO O •• l O 00 O 000 00 •* O 00 O : O 00 O 000 00*

• 0 0 0 0 0 0 0 0 0 O O O O O O O OO-OOO 00 00 00 O O 000 OOOOO 00 00 00 O O'

• 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 •OOOOOO 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00*00-000-00 OO-O-OO—O-O-OO-O-OO-OO-OO-O—OO»•O O O 00 C 00 O 00 000 :0 0000 O 00 00 00 00 O*O 00 OO 00 O 00 O 0000 00 O 0000 O 00 00 00 •000 00 00 O 00 000 O OOO OO O O O O OO O*00 O 00 O 000 00 O O O OO O ••00 O O O 00 00 OOOOO O 00 00 •O 00 O o O :0 00 O 000 O 00 O •

O O O O O : O O O O O 000 *• 0 0 0 0 l O O O O O O O O O *

•O O 0 : 0 O OO 000 O O O• O 0000 O 00 O O OO O*

• O 0 :0 O O O O 00 •• O 0 :0 O O 00 O •

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T-AJtIS ORIENTATIONStOUAl A»£A HOJtCTIO»LOMCK REMSMlUt

J0I104OS3

000000900000 O *

ooooooooooooooooooooooo o *•oooooooooooooooooooooooooooooo •

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OOOOOOOOOOOOOOOO 00000000000 OOOOOOOOOOOO 0000000000

00 OOOOOOOOOOOOO :0OO0O0000000O

OOOiO OOOOOOOOOOO00000000 OOOOOOOOOOOO

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HORIZONTAL CEVIATORIC STRESSRELATIVE Sitt AND

or coxmessioN

• , o •• OOOOOOO •

• 0000 0000000000000 •• ooooooooooooooooooo o •• OOOOOOOOOOOOOOOOOOOOOOO O OOOOO*

• oooooooooooooooooooooooo ooooooooooo• OOOOOOOOOOOOOOOOOOOO O OOOOOOOOOOOO• 000000000000000000 OOOOOOOOOOOOOOOO• OOOOOO OOOOOOOOOOOO 00000000000000000• o oooooooo o ooooooooooooooooooooooooo•OOOOOOOOOOOOOOO I OOOOOOOOOOOOOOOOOOOOOO

•OOOOOOOOOOOOOOOOOO I OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO : OOOOOOOOOOOOOOOOOOOOoooooooooooooooooooo ooooooooooooooooooooOOOOOOOOOOOOOOOOOOOO : OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOCOOOOO : OOOOOOOOOOOOOOOOOO*

OOOOOOOOOOOOOOOOOOOOOO : OOOOOOOOOOOOOOO*ooooooooooooooooooooooooo o oooooooo o •00000000000000000 OOOOOOOOOOOO OOOOOO •OOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOO •OOOOOOOOOOOO O OOOOOOOOOOOOOOOOOOOO •ooooocooooo oooooooooooooooooooooooo •

•OOOOO O OOOOOOOOOOOOOOOOOOOOOOO •• o ooooooooooooooooooo •* 0000000000000 0000 *

• OOOOOOO •

fAULT fUNE ORIENTATIONSCIVCN >T NOlUtAL VECTORStOUAL ARE* HOJtCTIOH J0II04053LOMEK HIHISfHtRt

L LCLLLLLLLLLbUb LLLLLLLLLLLLLL

bbbbLHRRbLbLLLLLLLLLLL LLRbbbbLbbbRRRRbbbbbbbLLLLl. L l l b b

RbbblLbMRRRRbbbbbbbbLLULLLLLLbbbbDHbtbbbbbRiiiutitbbbbbbbbbLLLl.LLLLLLbt.bbb

bbbbbbbbbbbbbRbbbbbLbLbLLLLLLLLLLLLLbbbbL•RbbbObbbbbbbbLbbLLLLLLLLlLLLLLLLLllLb L •• bbbbbbbbbbbbbbbbbbbLLl.LLll.LU.LLl. L •HRR bbbbbbbbbbbbbbbbLLLLLLLLLL •bbbbbR LRbbbbbbbbLbbbLLLLLLL •bbbbbb It bbbbbbbbbbbbbLLL R t ••LbbbbbbL LLLbbbbbbbbbbbbbLLLL ••LLbbbbbbb : bbbRbbbbbRbbbbbLLL L*•LLLbbbLD-Lbb-« RRRRRRRbbbbbbLLL—•LL L LbbbRR : MUtRRbbbbbbbtLLL*• LLLLRRbRRRRR R : MbbdbbbbbbbbL• L LLbRRbRbbbbRR : bbbbbbbbbb• LLLLLbbbbbbbbbbbbbbLR RbbbbbR• LLLLLbbRbbbbbbbbbbbbbbbRR R Rbb• LbLL^LbbbbbbbbbbbbbbbbbbRRRRM Hit '• LLLbLbLLLbRRbRRbbLbbbbDbbRbbbRRRRRRRRRRbR•bbbbbbbbbbbbbbbbbbbbbbbbbbbbR«bRR«bRbRbRibbbbbbbbbbbbbbbbbLbbbbbbbbRbbRRRbbbbblbbbbbbObbbbbbbbbbbbbbbbbRbRRRRRbbbbRLbbbbbbbbbbbbbbbbbbbbRKRRRRbbbR

bLb ILLbbbbbbRRRbRRRRRRRbRbLLLLLLLLLLbRbRRHRRR

L LLLLLLLL R

127

ORIGIN TIME 88 03 z^ 20H 28M 32.8S +/- 0.10SLATITUDE 67.463 +/- 0.012 DEG.LONGITUDE 24.287 +/- 0.013FOCAL DEPTH 5.4 +/- 3.5 KM

STASOSOMUGMUGKPMKPMSODSODLJVHAKHAKKLXKIRKIRVHK

ARR.PSPSPSPSPPSPPsp

202020202020202020202020202020

TIME282828282829282928282928292929

48.0058.5048.5459.8749.150.92

49.001.00

54.0054.379.89

59.620.50

20.108.73

RES.0.35

-0.07-0.02-0.270.08

-0.11-0.37-0.550.07

-0.12-0.530.030.25

-0.6'/-0.31

HEIGHT30.42.0

28.81.9

27.9•1.827.41.8

21.420.81.2

16.27.00.42.1

DIST.90.590.596.196.199.399.3101.1101.1129.2132.6132.6165.4169.8169.8232.4

AZIMUTH92.092.0

271.0271.0217.9217.994.794.7226.6244.3244.3200.1286.2286.2212.3

P UP

INPUT DATA

STN

MUGKPMLJVHAKKLXVMK

DIST.KM95.99.129.132.166.232.

FOR FAULT

AZIMUTHDEGREES

270.5216.9225.9243.7199.5211.9

PLANE SOLUTION

OMEGA(PZ)METER-SEC

+ 0.14E-080.48E-090.54E-090.46E-090.98E-090.25E-09

OMEGA(SZ)METER-SEC

0.44E-O80.25E-080.33E-080.14E-080.31E-080.12E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.949E+12 NmLOCAL MAGNITUDE: 2.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)9.lHz -16.2HZ ( 11.8HZ)

FAULT RADIUS RANGE 42m - 75m ( 58m)

STRESS DROP RANGE 0.95MPa - 5.37MPa ( 2.08MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 2.3mm - 7.3mm ( 3.9mm)

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 167. 28. degreesT-AXIS 123. -54.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -1 degreesTHE RELATIVE SIZE 0.42

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 119. 26. -33. degreesPLANE B 239. 76. 248.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 209. 64. degreesPLANE B 329. 14.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

11.35 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS21.9 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 63.1%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.23THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.29FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 4 % LEVEL(F-VALUE: F(ll, 8) - 3.32)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.22

129

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130

ORIGIN TIME 88 03 22 23H 58M 36.OS +/- 0.62SLATITUDE 65.426 +/- 0.038 DEG.LONGITUDE 22.609 +/- 0.042FOCAL DEPTH 9.1 +/- 3.2 KM

STA ARR. TIMEVMK P 23 58 45.14 0.00VMK S 23 58 51.82 -0.05

0.000.02

RES. WEIGHT DIST. AZIMUTH

KLX P 23 58 48.22KLX S 23 58 57.22KPM P 23 59 0.06 -0.05HAK P 23 59

44.7 55.2 301.53.3

36.02.5

55.2 301.574.374.

18.2 149,

14.914.95.0

3.97 0.13 6.8 174.0 344.7

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXHAK

DIST.KM54.74.

173.

AZIMUTHDEGREES

301.816.0345.0

OMEGA(PZ)METER-SEC0.54E-100.69E-100.11E-09

OMEGA(SZ)METER-SEC

0.15E-090.11E-090.15E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.926E+11 NmLOCAL MAGNITUDE: 1.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (:30km)13.1HZ -30.0H2 ( I8.8H2)

FAULT RADIUS RANGE 23m - 52m ( 36m)

STRESS DROP RANGE 0.28MPa - 3.33MPa ( 0.82MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.5mm - 2.4mm ( 1.0mm)

131

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 84. 5. degreesT-AXIS 173. -10.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 83 degreesTHE RELATIVE SIZE 0.98

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -51. 79. 184. degreesPLANE B 218. 86. -11.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 39. 11. degreesPLANE B 308. 4.

STATISTICAL INFORMATION

OF 0 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 0 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

3.61 % OF ALL MECHANISMS ARE ACCEPTABLE100.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS

3.6 % OF THESE FITTED ALSO THE AMPLITUDESTHE PART OF WELL FITTING PLANES IS 28.3%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.18THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.32FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 18 I LEVEL(F-VALUE: F( 5, 2) - 5.28)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.33S-WAVES 0.26

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133

ORIGIN TIME 88 03 29 06H 07M 37.5S +/- 0.99SLATITUDE 67.952 +/- 0.046 DEG.LONGITUDE 19.390 +/- 0.128FOCAL DEPTH 12.8 +/- 12.9 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUGMUGHAKHAKLJVKPM

PSPSPP

060606060606

070808080808

57.7713.161.2118.677.139.17

-0.020.370.02

-0.11-0.080.11

22.31.4

18.51.16.22.5

124.5124.5147.2147.2187.5201.3

114.8114.8140.2140.2139.3130.0

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKLJVKPM

DIST.KM

125.148.188.202.

AZIMUTHDEGREES

114.6139.9139.1129.8

OMEGA(PZ)METER-SEC

- 0.12E-080.37E-090.45E-090.57E-09

OMEGA(SZ)METER-SEC

0.35E-080.11E-080.31E-080.27E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.793E+12 NraLOCAL MAGNITUDE: 1.9

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.8HZ - 8.8Hz ( 6.6Hz)

FAULT RADIUS RANGE 78m - 143m ( 104m)

STRESS DROP RANGE 0.12MPa - 0.72MPa ( 0.30MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.5mm - 1.8mm ( 1.0mm)

134

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 87. 40. degreesT-AXIS 79. -50.

THE HORIZONTAL DEVIATOP.IC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -78 degreesTHE RELATIVE SIZE 0.11

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 29. 7. -55. degreesPLANE B 173. 85. 266.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 119. 83. degreesPLANE B 263. 5.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLAP.ITY MISFITS

AMPLITUDES FOR P AND S AT 4 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

28.99 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS59.1 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 93.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.18THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.27FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 19 % LEVEL(F-VALUE: F( 7, 4) - 2.60)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.26S-WAVES 0.21

155

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HEHISFHERE

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136

ORIGIN TIME 88 03 30 02H 21M 12.IS +/- 1.04SLATITUDE 65.220 +/- 0.068 DEG.LONGITUDE 20.032 +/- 0.126FOCAL DEPTH 8.0 +/- 6.5 KM

STA ARR. TIME RES.VMK P 02 21 26.59 0.00VMK S 02 21 37.27 -0.02KLX P 02 21 38.96 -0.03LJV P 02 21 42.08 0.11HAK P 02 21 44.03 -0.20

WEIGHT31.02.07.16.22.5

DIST.88.788.7

167.5187.4202.6

AZIMUTH53.953.954.330.319.3

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

VMKKLXLJVHAKKPM

DIST.KM89.

168.188.203.216.

AZIMUTHDEGREES

53.954.330.319.336.0

OMEGA(PZ)METER-SEC

+ 0.41E-090.11E-080.13E-080.49E-090.45E-09

OMEGA(SZ)METER-SEC

0.22E-080.73E-080.40E-080.10E-080.23E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.125E+13 NmLOCAL MAGNITUDE: 2.1

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)8.8HZ -12.9HZ ( 10.8Hz)

FAULT RADIUS RANGE 53m - 78m ( 63m)

STRESS DROP RANGE 1.13MPa - 3.57MPa ( 2.09MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 2.8mm - 6.1mm ( 4.3mm)

137

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 111. -69. degreesT-AXIS 103. 20.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 12 degreesTHE RELATIVE SIZE 0.38

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 189. 155. -84. degreesPLANE B 196. 66. 93.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 99. 65. degreesPLANE B 286. 24.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

28.75 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS56.9 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 93.0%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.34THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.46FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS NOT SIGNIFICANTNOT EVEN AT 50 % LEVEL(F-VALUE: F( 9, 6) « 0.93)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.26S-WAVES 0.27

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3.9

ORIGIN TIME 88 03 30 12H 06M 35.OS +/- 0.33SLATITUDE 67.518 +/- 0.019 DEG.LONGITUDE 22.413 +/- 0.045FOCAL DEPTH 8.9 +/- 3.2 KM

STAMUGMUGHAKHAKKPMKPMLJVLJVKLX

ARRPSPSPSPSP

121212121212121212

. TIME060606060607060707

38.1440.4347.4756.7549.380.0151.022.221.35

RES.0.00

-0.03-0.020.08

-0.03-0.010.12

-0.38-0.05

WEIGHT75.27.135.32.4

31.22.1

28.51.8

16.3

DIST.17.017.075.975.987.987.997.197.1164.3

AZINUTH248.4248.4209.5209.5165.7165.7186.5186.5170.2

P UP

INPUT DATA

STN

HAKKPMLJVKLXVMKMUG

DIST.KM76.88.97.

165.209.17.

FOR FAULT

AZIMUTHDEGREES

209.4165.7186.4170.1190.5247.6 +

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.12E-090.19E-090.18E-090.26E-090.81E-100.00E+00

OMEGA(SZ)METER-SEC

0.34E-090.52E-090.10E-080.43E-090.40E-090.0OE+0O

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.270E+12 NmLOCAL MAGNITUDE: 1.4

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)6.6H2 - 9.1HZ ( 7.9Hz)

FAULT RADIUS RANGE 75m - 104m ( 87m)

STRESS DROP RANGE O.lOMPa - 0.27MPa ( 0.18MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.3mm - 0.7mm ( 0.5mm)

140

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 149. 11. degreesT-AXIS 63. -19.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -28 degreesTHE RELATIVE SIZE 0.93

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 105. 69. -6. degreesPLANE B 197. 84. 202.-

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 195. 21. degreesPLANE B 287. 6.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

9.61 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS18.8 I OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 58.0%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.25THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.34FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 17 % LEVEL(F-VALUE: F( 9, 6) - 2.26)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.22S-WAVES 0.21

141

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142

ORIGIN TIME 88 04 01 01H 36M 10.5S +/- 0.38SLATITUDE 67.493 +/- 0.023 DEG.LONGITUDE 22.195 +/- 0.046FOCAL DEPTH 9.0 +/- 2.2 KM

STAMUGMUGHAKKPMKPMLJVKLXKLXVMK

ARR.PSPPSPPSS

010101010101010101

TIME363636363636363637

12.4013.6021.8124.8435.4326.1136.5955.887.59

RES.0.02

-0.19-0.07-0.07-0.100.28

-0.16-0.530.43

WEIGHT88.09.038.031.22.129.516.40.90.1

DIST.7.37.369.288.088.093.7

163.4163.4204.3

AZIMUTH241.8241.8203.7159.2159.2180.8166.6166.6187.9

P UP

INPUT DATA

STN

HAKKPMLJVKLXVMKMUG

DIST.KM69.88.93.

163.204.7.

FOR FAULT

AZIMUTHDEGREES

204.0 +159.2180.9166.6187.9244.8 +

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.94E-100.15E-090.10E-090.13E-090.76E-10O.OOE+00

OMEGA(SZ)METER-SEC

0.22E-090.42E-090.43E-090.68E-090.38E-090.00E+00

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.110E+12 NmLOCAL MAGNITUDE: 1.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)12.6HZ -22.0HZ ( 15.9H2)

FAULT RADIUS RANGE 31m - 54m ( 43m)

STRESS DROP RANGE 0.29MPa - 1.56MPa ( 0.59MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.5nun - 1.6mm ( 0 .8mm)

143

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 146. 40. degreesT-AXIS 48. 9.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -38 degreesTHE RELATIVE SIZE 0.78

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 103. 70. 37. degreesPLANE B 179. 124. 204.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 193. 20. degreesPLANE B 89. 34.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

6.47 % OF ALL MECHANISMS ARE ACCEPTABLE23.4 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS27.6 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 55.2%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.16THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.22FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 8 % LEVEL(F-VALUE: F( 9, 6) - 3.23)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.25S-WAVES 0.16

144

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145

ORIGIN TIME 88 04 04 02H 25M 22.9S +/- 0.73SLATITUDE 67.779 +/- 0.032 DEG.LONGITUDE 19.621 +/- 0.097FOCAL DEPTH 8.2 +/- 4.2 KM

STAMUGMUGHAKHAKLJVLJVKPMKLXVMK

ARR.PSPSPSPPP

020202020202020202

TIME252525252526252626

40.7553.9343.6558.4449.7910.3051.980.030.88

RES.-0.020.100.02

-0.350.040.53

-0.03-0.04-0.10

WEIGHT25.61.6

21.91.3

16.00.96.42.01.9

DIST.108.6108.6126.2126.2166.6166.6181.7242.1249.5

AZI107.7107.7138.0138.0137.6137.6127.4140.5158.8

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKLJVKPM

DIST.KM

109.127.167.182.

AZIMUTHDEGRESS

107.9137.9137.6127.4

OMEGA(PZ)METER-SEC0.39E-09

- 0.20E-090.25E-090.36E-09

OMEGA(SZ)METER-SEC

0.29E-080.70E-090.12E-080.12E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.491E+12 NmLOCAL MAGNITUDE: 1.7

SHEAR WAVE CORNER FREQUENCY KANGE AT CLOSE DISTANCES (130km)4.8Hz - 8.4Hz ( 6.4Hz)

FAULT RADIUS RANGE 82m - 143m ( 107m)

STRESS DROP RANGE 0.07MPa - 0.39MPa ( 0.17MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.3mm - 1.Onun ( 0.6mm)

146

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 103. -29. degreesT-AXIS 27. 24.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -70 degreesTHE RELATIVE SIZE 0.77

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 67. 129. -4. degreesPLANE B 154. 87. 141.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 337. 39. degreesPLANE B 244. 3.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 4 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

31.54 % OF ALL MECHANISMS ARE ACCEPTABLE50.0 % ACCEPTABLE DUE TO FIRST MOTION OBSFRVATIONS62.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 95.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.14THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.21FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 24 % LEVEL(F-VALUE: F( 7, 4) - 2.14)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.24S-WAVES 0.19

147

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LLbLbbbbbbbbbbORbbbbbbbbbbbbbbRbbRRbLLbL-LbLLbbbBbbbbbbbObRbbbbbbbbbbRbbbbbbLLLblLLO

LLLLI.bbbbbbbbbbbbbbbbbbbbbbbbbbbbbLLLLl.l.LblbbLbLbbbbbbbbbbbbbbbbbbbbbbbbbbbbbLLLLLLLLLtLLL

LbLLbbbbbObbbbbbbbbbbbbbbbbbbbLLl!.bbbLbb[.!.ll.(.bbLbLbLbbbbbbbbbbbbbbbbbbbbbbbbLLLbbbbLbLbbbLLLLbL

tLLLLbbbbbbbbbbbbbbbbbbbbbbLbLbbbbbbLbbLbblLbLbLbibLLbbbbbbbbbbbbbbbbbbbbbbLLtbbbbbbbbbLbbLbbbLLLbILLLLbbbbbbbbbbbbbbbbbbRbLLLLLbbbbbbbbbbbbbbbLbLbLLLLLbbbbbbbbbbbbt.bbbbbRRbRRbbbbbbbbbbbbbbbbbLLl.btLLLLbLbbbbbbbbbLbbbbRbbbbRbbbbbbbbbbbbbbbbbblbLbLLLLLbbLbbbbbbLbbRRbbbbbbbbbbbbbbbbbbbbbbDbbLLbLLLLLLbbbbbLbbbbRRRbbbbbbbbbbbbbbbbbbbbbbbbbbLbLLLLLLbbbLbbbbRRRbbbbbbbbbbbbbbbbbbbbbbbbbbbLbLOOllLbbbbbRRRbRbbbbbbbbbbbbbbbbbbbbbbbbbbLLbLLLlLbbbRRRRbRbRbbbbbbbbbbbbbbbbbbbbbbbbLLbLlLLbbRbRRRRbKbbbbbbbbbbbbbbbbbbbbbbbbbbb

LbRRbl>l<RI>bbbbbbbbbbbbbbbbbbbbbbbbbbI.bL•bbRRRR RRRbbbbbRbbbbbbbbbbbbftbbbbb•RbRb RRbbbRbbRbbbbbbbbbbbbbbb

RRR RRbbbbRbbbbbbbRbRbbb• RRRRbRbRRRbbRb

II UK RbRb

146

ORIGIN TIME 88 04 04 02H 33M 16.2S +/- 0.18SLATITUDE 67.662 +/- 0.012 DEG.LONGITUDE 22.114 +/- 0.034FOCAL DEPTH 8.6 +/- 2.2 KM

STAMUGMUGKIRKIRHAKKPMKPMLJVLJVKLXKLXSOSOVMKVMK

ARR.020202020202020202020202020202

TIME33 20.33 23.33 28.33 36.33 30.33 33.33 46.33 34.33 48.33 45.34 7.33 46.34 8.33 50.34 18.

RES.10 -0.0222 0.1950 0.0750 -0.9536 0.1239 -0.27

0.110.020.44

21 -0.1217 -0.0100 0.3500 0.2359 -0.2540 1.33

635954

WEIGHT DIST.69.2 22.56.235.82.5

31.9

24.71.56.4

22.574.674.6•85.7

26.0 1061.6 106.9

112.5112.5182.6

0.4 182.66.3 184.80.3 134.82.2 222.50.1 222.5

AZIMUTH187.6187.6286.3286.3196.5160.9160.9178.8178.8166.8166.896.496.4

186.3

P DOWN

P DOWN

P DOWN

186.3

INPUT DATA

STN

MUGHAKKPMLJVKLXVMK

DIST.KM26.90.

109.116.185.226.

FOR FAULT

AZIMUTHDEGREES

194.6 -198.2163.4 -180.7 -168.2187.2

PLANE SOLUTION

OMEGA(PZ)METER-SEC0.19E-080.47E-090.73E-090.47E-090.91E-090.39E-09

OMEGA(SZ)METER-SEC

0.15E-070.17E-080.33E-080.32E-080.53E-080.28E-08

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.101E+13 NmLOCAL MAGNITUDE: 2.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.7HZ - 9.6H2 ( 7.0HZ)

FAULT RADIUS RANGE 71m - 146m ( 98m)

STRESS DROP RANGE 0.14MPa - 1.19MPa ( 0.46MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.7mm - 2.7mm ( 1.5mm)

14 9

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 162. -29. degreesT-AXIS 64. -14.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -22 degreesTHE RELATIVE SIZE 0.84

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 115. 100. -32. degreesPLANE B 199. 59. 169.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 25. 10. degreesPLANE B 289. 31.

STATISTICAL INFORMATION

OF 3 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 3 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 6 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

8.77 % OF ALL MECHANISMS ARE ACCEPTABLE32.3 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS27.2 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 58.3%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.27THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.35FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 34 % LEVEL(F-VALUE: F(ll, 8) - 1.35)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.27S-WAVES 0.22

ISO

-AXIS ORIENTATIONSEQUAL AREA PROJECTION JO9S02332LOWER HEH1SPHERE

0 0 *0 00 O 0:0 •

0*00 00 O O ! •O 00 O O 00 000 *

• 00 O O OO OOOsO O O O O •* O O 00 00 O 0000 O O O O O

* OOOO 00 O 0000 O O O 00 O• O O O O O O O O O O O O O O 0000• OO 0000 00 O: O 00 O O• 0 0 : 00 O O• O I O O O• : O O

•O O :O 00 O O :

0 0 0 0 :OO O o :

OO O O t•O OOOO O I i

0 0 0 0 0 : 0 0 0 0 00*00 0 0 0 0:0 O O 00 O •

•0 0 0 O:OOOO O •O 0:0

T - A I I S ORIENTATIONSEQUAL AREA PROJECTIONLOMEI HEMISPHERE

O000

• O OOOOOOOOOO : 000* OOOOOOOOOOOOOOOOQDO O 00000 000

< ooooooooooooooooooooooooooooooooooo oo«* oooooooooooooooooooooooooooooooooooooo*OOOOOOOOOO 000 00 00 :00OOO0OOO00000O0000OO00*•ooooooooo ooooo i oooooooooooooooooooo •oooooooooooooooooooo 10 O OOOOOOOOOOOOOOooooooooo^wooooooooooooooowjooooooooooooo o

oooooooooooooooooooooooooooooooooooooooo•ooooooooooooooooooooooooooooooooo o

• OOOO O 0 0 OOOOOOOOOOO '

HORIZONTAL DEVIATORIC STRESSRELATIVE SIZE AND JO9S033ORIENTATION OP COMPRESSION

• OOOOOO: ••0000000000000 O •

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• oooooooooooooooooooooo• oooooooooooooooooooo

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TAVLT PLANE ORIENTATIONSGIVEN BY NORMAL VECTORSEQUAL AREA PROJECTIONLOWER HEMISPHERE

J0950J332

L ; RP.RR»LLLL : RP.ORRRR

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•Lt.LLL[.:.t.LI.I.LU.bLbbbbbbbbbbbbbRR!iRRRRR •LLLLLLLLLLLLLLLbbbbbRftRftbbbbRbbbRRRRRRR •

•LLLLLLLLLLL : KbbRbbbRRRR •• LL LLLLLLLLL : HRRbbRbHRIIRR • » •

*L LLLLLLLLLLLLLLLXLLb : KRRRRRbRbRbRRRRFRRR• LLLLOOOLLLLLLLlLLLbbbbbbRRRRRRbbRRRR RP.

LLLLLLLLlLLI,LLbbbbbbbbP.RP.ItRRRR LLLLLLLLUbbbRRbR

RltbRbRb L :RRRbbbbbbbbb :

R • RRRbbbbbbbbbbbLLLLLL LR R RRRRRbbbbbbbbbbbbbbLLLLLLLLLLLLLLLL

•RRRLRl KRORbbbbbbbbbbbbLLLLLLLLLLLLLL L*•KRRRbRL RRRMIbRbbbbbbbLLLLLLLLLbLLLLLLL

RRRbKbbLL Lb bRLbbbRbbbbbLLLLLRRMbRbLbL L RRRRRRRRRRbRHbRLllLl.'

MRRRRbRbbbbbRbRRRRmbbbbbRbLLL«RRR«6bl>t.bbbbbbbbbbbbbbLLLL

RltKRRRbtbbbbbbbLLLI.R »R R

157

ORIGIN TIME 88 04 04 17H 48M 34.8S +/- 0.08SLATITUDE 66.387 +/- 0.005 DEG.LONGITUDE 22.601 +/- 0.025FOCAL DEPTH 18.5 +/- 1.6 KM

STALJVLJVKLXKLXKPMKPMHAKHAKVMKVMK

ARR.PSPSPSPSPs

17171717171717171717

TIME48484848484848484849

41.3346.1942.0847.4042.4348.0247.4456.7149.760.37

RES.-0.010.060.020.00

-0.02-0.060.04

-0.040.01

-0.52

WEIGHT57.44.753.64.351.84.135.42.4

30.12.0

DIST.35.635.640.640.643.343.375.775.791.491.4

AZIMUTH327.2327.2151.4151.418.018.0322.9322.9210.7210.7

P UP

P UP

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN DIST.KM35,41,

LJVKLXKPMHAK

43.75.

VMK 92.

AZIMUTHDEGREES

327.1151.518.2322.8210.6

OMEGA(PZ)METER-SEC

+ 0.79E-10+ 0.83E-10+ 0.56E-10

0.49E-100.13E-10

OMEGA(SZ)METER-SEC

0.21E-090.26E-090.19E-090.31E-090.98E-10

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.377E+11 NraLOCAL MAGNITUDE: 0.6

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)4.7HZ - 7.0HZ ( 6.0Hz)

FAULT RADIUS RANGE 98m - 146m ( 115m)

STRESS DROP RANGE O.OlMPa - 0.02MPa ( O.OlMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.0mm ( 0.0mm)

752

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 66. 22. degreesT-AXIS 160. 9.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 67 degreesTHE RELATIVE SIZE 0.91

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -69. 81. 157. degreesPLANE B 205. 113. -10.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 21. 9. degreesPLANE B 115. 23.

STATISTICAL INFORMATION

OF 3 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 3 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.07 % OF ALL MECHANISMS ARE ACCEPTABLE13.8 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS7.8 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 17.2%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.24THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.32FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 4 % LEVEL(F-VALUE: F( 9, 6) - 4.19)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.22S-WAVES 0.30

253

-AXIS ORICNTATIONSCOUAL A»CA PROJECTIONLOWER HEMISPHERE

T - A I 1 3 ORIENTATIONSEQUAL M E * PROJECTIONLOVER REMSPHERE

00000*

J09S174I4

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t O O O 00 O O*O OO 00 O O

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• ocOOOOOOOOOO 00OOOOOOOOOOOOOO0000 0000000

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OOOOOO 00 O*OOOOOOOOOOOOOOooooooooo ooooo

OOOOOOO 0 0 0 0OOOOOOOOOOOOOO

oo oooooooooo00*

FAULT PLANE OKIENTATIOMSGIVEN BY NORMAL VECTORSEQUAL AREA PROJECTION J 0 9 5 1 7 4 I 4LOWER HEMISPHERE

• I ILL L• : LLLLOLOLLL*L

• LLLLLLLLLLLLL LL L• IU.LILLLLL

RR R LLLLLLLLL• RRRIIRR RbbbbLLLLLLL

•RRRRRRRRRRRRbbbbbL L:•RR :

t

RRRRHRRRRRRRftRRORRR

LL LLLL•LLLLLLLLL

LLLLLLLLULL

L*

I LbbRRRRRRRRR RRRRR*L LLbRRRRR R R •

LLL LLLL L R

154

ORIGIN TIME 88 04 07 21H 24M 31.6S +/-LATITUDE 67.974 +/- 0.033 DEG.LONGITUDE 20.781 +/- 0.092FOCAL DEPTH 29.1 +/- 2.5 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUG P 21 24 44.64 -0.04 34.4 78.4 136.3MUG S 21 24 54.83 0.34HAK P 21 24 51.16 0.07HAK S 21 25 5.07 -0.67LJV S 21 25 15.13 -0.09KPM P 21 24 57.08 -0.01KPM S 21 25 16.69 0.21

2.3 78.4 136.322.8 121.9 163.71.4 121.9 163.71.0 159.0 157.3

16.3.164.0 145.10.9 164.0 145.1

P DOWN

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKKPM

DIST.KM78.121.164.

AZIMUTHDEGREES

136.0163.7145.0

OMEGA(PZ)METER-SEC

- 0.17E-090.88E-100.54E-10

OMEGA(SZ)METER-SEC

0.55E-090.36E-090.70E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.148E+12 NmLOCAL MAGNITUDE: 1.2

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)6.8Hz -10.2HZ ( 8.4HZ)

FAULT RADIUS RANGE 67m - 101m ( 82m)

STRESS DROP RANGE 0.06MPa - 0.2lMPa ( 0.12MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.2mm - 0.4mm ( 0.2mm)

55

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 178. -18. degreesT-AXIS 96. 23.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 1 degreesTHE RELATIVE SIZE 0.87

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 136. 120. 4. degreesPLANE B 223. 93. 150.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 46. 30. degreesPLANE B 138. 3.

STATISTICAL INFORMATION

OF 1 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 1 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 3 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

13.78 I OF ALL MECHANISMS ARE ACCEPTABLE50.0 I ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS27.3 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 86.2%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.20THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.38FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 43 % LEVEL(F-VALUE: F( 5, 2) - 1.67)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.34S-WAVES 0.24

15C

-AXIS ORIENTATIONSEQUAL AlltA HOJtCTIONLOMCR HEMSrKtRC

J0*t2U<5T-AXJS ORIENTATIONS(ou*i *»" ncjtctioHion* icnisnicK

• 0 O:0 0 0 »• 0 0 00000 00 O Q O •

• 00 O O 00 OOOO O O O O •• 00 O O 00 0OO:0 0 0 '

* O O 00 OO O OOOO O O O O O •• OOOOOO OO O OOOO O O O OO O O 0 0*

• O O O O O O O O O O O O O O O O 0 0 0 O •• O O O OO OOOO 00 Oi O O OO OO •OO 000 OO 00 000 I O OO*OO OO O 00 00 O O t 00*000 OO 00 OO 0 0 : 0 0 0 OO O O*

' 0 0 0 0 0 0 0 : 00 00 OO O O *00 O 000 0 0 0 : 00 O O OO O O •oo-ooo-oo-oo-o o o-oo-oo-oo-o •-o o o oo o o .- o oo oo oo o*o oo oo oo o o i oo ooo oo •

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15:

ORIGIN TIME 88 04 08 18H 51M 10.OS +/- 0.45SLATITUDE 67.539 +/- 0.026 DEG.LONGITUDE 22.665 +/- 0.051FOCAL DEPTH 4.3 +/- 4.8 KM

STA ARR. TIME RES. WEIGHT DIST. AZIMUTHMUGMUGKPMKPMLJVKLX

PSPSSP

181818181818

515151515151

14.6518.1324.4635.2039.0836.83

0.000.020.000.08

-0.210.00

63.75.5

31.02.11.7

16.2

28.128.188.488.4104.2165.4

252.0252.0173.2173.2193.1174.3

P

P

DOWN

UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

MUGHAKKPMLJVKLX

DIST.KM28.84.88.101.165.

AZIMUTHDEGREES

252.2215.5173.3192.7174.3

OMEGA(PZ)METER-SEC

- 0.43E-090.53E-10

+ 0.69E-100.72E-100.65E-10

OMEGA(SZ)METER-SEC

0.35E-090.14E-090.18E-090.24E-090.12E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.913E+11 NmLOCAL MAGNITUDE: 1.0

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)9.7HZ -14.2Hz ( 11.7HZ)

FAULT RADIUS RANGE 48m - 71m ( 58m)

STRESS DROP RANGE O.llMPa - 0.3lMPa ( 0.19MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.3mm - 0.5mm ( 0.4mm)

158

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 61. 5. degreesT-AXIS -27. -23.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 62 degreesTHE RELATIVE SIZE 0.92

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A 15. 70. -13. degreesPLANE B 109. 78. 200. •

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 105. 20. degreesPLANE B 199. 12.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 5 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

2.37 % OF ALL MECHANISMS ARE ACCEPTABLE31.0 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS7.7 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 26.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.20THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.26FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT BETTER THAN 1 % LEVEL(F-VALUE: F( 9, 6) - 9.23)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.38S-WAVES 0.22

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ORIGIN TIHE 88 04 10 19H 48M 10.6S +/" 0.24SLATITUDE 66.175 +/- 0.006 DEG.LONGITUDE 21.904 +/- 0.023FOCAL DEPTH 9.6 +/- 14.5 KM

STA ARR. TIMEKLX P 19 48 19.34 0.05

S 19 48 25.56 -0.14

RES. WEIGHT DIST. AZIMUTH46.2 52

KLX S 19 48 25.56 -0.14 3.5 52,LJV P 19 48 19.70 0.02 44.9 54,LJV S 19 48 26.56 0.19 3.3 54VMK P 19 48 20.13 0.09 43.7 57,VMK S 19 48 25.90 -1.10 3.2 57,KPM P 19 48 23.43 -0.10 34.3 78,KPM S 19 48 32.79 -0.26 2.3 78,

4 102.84 102.8

12.312.3194.8194.834.234.2

P DOWN

P UP

INPUT DATA FOR FAULT PLANE SOLUTION

STN

KLXLJVVMKKPM

DIST.KM53.54.58.78.

AZIMUTHDEGREES

103.312.6194.534.5

OMEGA(PZ)METER-SEC

- 0.58E-100.46E-100.66E-10

+ 0.57E-10

OMEGA(SZ)METER-SEC

0.95E-100.31E-090.87E-100.16E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.470E+11 NmLOCAL MAGNITUDE: 0.7

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)-0.7HZ - 6.5Hz ( 4.3Hz)

FAULT RADIUS RANGE 106m —985m ( 160m)

STRESS DROP RANGE O.OOMPa - 0.02MPa ( O.OOMPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.0mm - 0.lmm ( 0.0mm)

161

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 126. 11. degreesT-AXIS 212. -18.

THE HORIZONTAL DEVIATORIC STRESS AS GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION -55 degreesTHE RELATIVE SIZE 0.93

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -10. 69. 186. degreesPLANE B 258. 85. -21."

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 80. 21. degreesPLANE B 348. 5.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 4 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

1.51 % OF ALL MECHANISMS ARE ACCEPTABLE28.6 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS5.3 I OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 21.1%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.19THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.28FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 4 % LEVEL(F-VALUE: F( 7, 4) - 6.24)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.27S-WAVES 0.27

161

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ORIGIN TIME 88 04 16 17H 56M 34.4S +/- 0.33SLATITUDE 66.312 +/- 0.007 DEG.LONGITUDE 23.738 +/- 0.060FOCAL DEPTH 6.2 +/- 4.0 KM

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TIME56565656565657575657

41.3446.4644.5251.7857.1453.818.028.28

58.5216.74

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WEIGHT52.74.2

41.33.02.323.51.41.4

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. AZIMUTH229.7229.7323.5323.5299.3306.3306.3235.2330.7330.7

P DOWN

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INPUT DATA FOR FAULT PLANE SOLUTION

STN DIST.KM

KLX 42.KPM 62.HAK 119.VMK 121.

AZIMUTHDEGREES

230.1323.6306.4235.3

OMEGA(PZ)METER-SEC

- 0.89E-10+ 0.10E-09

0.66E-100.91E-10

OMEGA(SZ)METER-SEC

0.16E-090.50E-090.24E-090.21E-09

DYNAMIC SOURCE PARAMETERS

SIZE MEASURESSEISMIC MOMENT: 0.849E+11 NmLOCAL MAGNITUDE: 0.9

SHEAR WAVE CORNER FREQUENCY RANGE AT CLOSE DISTANCES (130km)5.9HZ -13.6HZ ( 9.lHz)

FAULT RADIUS RANGE 50m - 116m ( 75m)

STRESS DROP RANGE 0.02MPa - 0.28MPa ( 0.09MPa)

RANGE OF THE PEAK SLIP AT THE FAULT 0.lnim - 0.5mm ( 0.2mm)

164

THE ORIENTATION OF THE RELAXED STRESSAZIMUTH DIP

P-AXIS 82. -18. degreesT-AXIS 164. 22.

THE HORIZONTAL DEVIATORIC STRESS AS- GIVEN BY THE P- AND T-AXESTHE AZIMUTH OF COMPRESSION 78 degreesTHE RELATIVE SIZE 0.87

THE TWO POSSIBLE FAULT PLANESSTRIKE DIP SLIP

PLANE A -56. 119. 177. degreesPLANE B 212. 93. 29.

THE NORMAL DIRECTIONS OF THE FAULT PLANESAZIMUTH DIP

PLANE A 214. 29. degreesPLANE B 122. 3.

STATISTICAL INFORMATION

OF 2 FIRST MOTION POLARITY OBSERVATIONSAT LEAST 2 ARE REQUIRED TO FIT

THE OPTIMUM MECHANISM HAS 0 POLARITY MISFITS

AMPLITUDES FOR P AND S AT 4 STATIONS ARE USEDONLY MECHANISMS GIVING AN ESTIMATED STANDARDDEVIATION OF THE AMPLITUDE ERROR FACTOR OF LESSTHAN 1.60 FOR SINGLE P-WAVE OBSERVATIONS ARETAKEN AS ACCEPTABLE AND INCLUDED IN THE FIGURES

3.49 % OF ALL MECHANISMS ARE ACCEPTABLE32.4 % ACCEPTABLE DUE TO FIRST MOTION OBSERVATIONS10.8 % OF THESE FITTED ALSO THE AMPLITUDES

THE PART OF WELL FITTING PLANES IS 42.6%

THE AMPLITUDE FIT OF THE OPTIMAL MECHANISMGIVES A MEAN ERROR FACTOR OF 1.10THIS CORRESPONDS TO A STANDARD DEVIATION FACTOR OF 1.14FOR SINGLE P-WAVE OBSERVATIONS

THE DOUBLE COUPLE SOLUTION IS SIGNIFICANTAT 2 % LEVEL(F-VALUE: F( 7, 4) - 10,03)

THE MEASURE OF THE MISFIT TO AN EARTHQUAKE SPECTRUMP-WAVES 0.23S-WAVES 0.25

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List of SKB reports

Annual Reports1977-78TR121KBS Technical Reports 1-120.Summaries. Stockholm, May 1979.

1979TR 79-28The KBS Annual Report 1979.KBS Technical Reports 79-01 - 79-27.Summaries. Stockholm, March 1980.

1980TR 80-26The KBS Annual Report 1980.KBS Technical Reports 80-01 - 80-25.Summaries. Stockholm, March 1981

1981TR81-17The KBS Annual Report 1981.KBS Technical Reports 81-01 -81-16.Summaries. Stockholm, April 1982.

1982TR 82-28The KBS Annual Report 1982.KBS Technical Reports 82-01 - 82-27Summaries. Stockholm, July 1983.

1983TR 83-77The KBS Annual Report 1983.KBS Technical Reports 83-01 -83-76Summaries. Stockholm, June 1984.

1984TR 85-01Annual Research and Development Report1984Including Summaries of Technical Reports Issuedduring 1984. (Technical Reports 8401-84-19)Stockholm June 1985.

1987TR 87-33SKB Annual Report 1987Including Summaries of Technical Reports Issuedduring 1987Stockholm, May 1988

1988TR 88-32SKB Annual Report 1988Including Summaries of Technical Reports Issuedduring 1988Stockholm, May 1989

Technical Reports

7989TR 89-01Near-distance seismological monitoring ofthe Lansjärv neotectonic fault regionPart II: 1988Rutger Wahlström, Sven-Olof Linder,Conny Holmqvist, Hans-Edy MårtenssonSeismological Department, Uppsala University,UppsalaJanuary 1989

TR 89-02Description of background data in SKBdatabase GEOTABEbbe Eriksson, Stefan SehlstedtSGAB, LuleåFebruary 1989

TR 89-03Characterization of the morphology,basement rock and tectonics in SwedenKennert RöshoffAugust 1988

1985TR 85-20Annual Research and Development Report1985Including Summaries of Technical Reports Issuedduring 1985. (Technical Reports 85-01-85-19)Stockholm May 1986.

1986TR 86-31SKB Annual Report 1986Including Summaries of Technical Reports Issuedduring 1986Stockholm, May 1987

TR 89-04SKB WP-Cave ProjectRadionuclide release from the near-field ina WP-Cave repositoryMaria Lindgren, Kristina SkagiusKemakta Consultants Co, StockholmApril 1989

TR 89-05SKB WP-Cave ProjectTransport of escaping radionuclides fromthe WP-Cave repository to the biosphereLuis Moreno, Sue Arve, Ivars NeretnieksRoyal Institute of Technology, StockholmApril 1989

TR 89-06SKB WP-Cave ProjectIndividual radiation doses from nuclidescontained in a WP-Cave repository forspent fuelSture Nordlinder, Ulla BergströmStudsvik Nuclear, StudsvikApril 1989

TR 89-07SKB WP-Cave ProjectSome Notes on Technical IssuesPart 1: Temperature distribution in WP-Cave: when

shafts are filled with sand/water mixturesStefan Björklund, Lennart JosefsonDivision of Solid Mechanics, Chalmers Uni-versity of Technology, Gothenburg, Sweden

Part 2: Gas and water transport from WP-Caverepository Luis Moreno, Ivars NeretnieksDepartment of Chemical Engineering, RoyalInstitute of Technology, Stockholm, Sweden

Part 3: Transport of escaping nuclides from theWP-Cave repository to the biosphere.Influence of the hydraulic cageLuis Moreno, Ivars NeretnieksDepartment of Chemical Engineering, RoyalInstitute of Technology, Stockholm, Sweden

August 1989

TR 89-08SKB WP-Cave ProjectThermally incuded corrective motion ingroundwater in the near field of theWP-Cave after filling and closurePoiydynamics Limited, ZurichApril 1989

TR 89-09An evaluation of tracer tests performedat StudsvikLuis Moreno1, Ivars Neretnieks1, Ove Landström21 The Royal Institute of Technology, Department of

Chemical Engineering, Stockholm2 Studsvik Nuclear, NyköpingMarch 1989

TR 89-10Copper produced from powder by HIP toencapsulate nuclear fuel elementsLars B Ekbom, Sven BogegårdSwedish National Defence Research EstablishmentMaterials department, StockholmFebruary 1989

TR 89-11Prediction of hydraulic conductivity andconductive fracture frequency by multi-variate analysis of data from the Klipperåsstudy siteJan-Erik Andersson1, Lennart Lindqvist2

1 Swedish Geological Co, Uppsala2 EMX-system AB, LuleåFebruary 1988

TR 89-12Hydraulic interference tests and tracer testswithin the Brendan area, Finnsjön study siteThe Fracture Zone Project - Phase 3Jan-Erik Andersson, Lennart Ekman, Erik Gustafsson,Rune Nordqvist, Sven TirénSwedish Geological Co, Division of EngineeringGeologyJune 1988

TR 89-13Spent fuelDissolution and oxidationAn evaluation of literature dataBernd GrambowHanh-Meitner-lnstitut, BerlinMarch 1989

TR 89-14The SKB spent fuel corrosion programStatus report 1988Lars O Werme1, Roy S Forsyth2

1 SKB, Stockholm2 Studsvik AB, NyköpingMay 1989

TR 89-15Comparison between radar data andgeophysical, geological and hydrologicalborehole parameters by multivariateanalysis of dataSerje Carlsten, Lennart Lindqvist, Olle OlssonSwedish Geological Company, UppsalaMarch 1989

TR 89-16Swedish Hard Rock Laboratory -Evaluation of 1988 year pre-investigationsand description of the target area, theisland of ÄspöGunnar Gustafsson, Roy Stanfors, Peter WikbergJune 1989

TR 89-17Field instrumentation for hydrofracturingstress measurementsDocumentation of the 1000 m hydro-fracturing unit at Luleå University ofTechnologyBjarni Bjarnason, Arne TorikkaAugust 1989

TR 89-21Rock quality designation of the hydraulicproperties in the near field of a final repo-sitory for spent nuclear fuelHans Carlsson1, Leif Carlsson1, Roland Pusch2

1 Swedish Geological Co, SGAB, Gothenburg,Sweden

2 Clay Technology AB, Lund, SwedenJune 1989

TR 89-18Radar investigations at the Saltsjötunnelpredicitions and validationOlle Olsson1 and Kai Palmqvist21 Abem AB, Uppsala, Sweden2 Bergab, GöteborgJune 1989

TR 89-19Characterization of fracture zone 2,Finnsjön study-siteEditors: K. Ahlbom, J.A.T. Smellie, Swedish

Geological Co, UppsalaPart 1: Overview of the fracture zone project at

Finnsjön, SwedenK. Ahlbom and J.A.T. Smellie. SwedishGeological Company, Uppsala, Sweden.

Part 2: Geological setting and deformation history ofa low angle fracture zone at Finnsjön,SwedenSven A. Tirén. Swedish Geological Com-pany, Uppsala, Sweden.

Part 3: Hydraulic testing and modelling of a low-angle fracture zone at Finnsjön, SwedenJ-E. Andersson1, L. Ekman1, R. Nordqvist1

and A. Winberg2

1 Swedish Geological Company, Uppsala,Sweden

2 Swedish Geological Company, Göteborg,Sweden

Part 4: Groundwater flow conditions in a low anglefracture zone at Finnsjön, SwedenE. Gustafsson and P. Andersson. SwedishGeological Company, Uppsala, Sweden

Part 5: Hydrochemical investigations at Finnsjön,SwedenJ.A.T. Smellie1 and P. Wikberg2

1 Swedish Geological Company, Uppsala,Sweden

2 Swedish Nuclear Fuel and Waste Manage-ment Company, Stockholm, Sweden

Part 6: Effects of gas-lift pumping on hydraulic bore-hole conditions at Finnsjön, SwedenJ-E- Andersson, P. Andersson and E. Gus-tafsson. Swedish Geological Company, Upp-sala, SwedenAugust 1989

TR 89-20WP-Cave - Assessment of feasibility,safety and development potentialSwedish Nuclear Fuel and Waste ManagementCompany, Stockholm, SwedenSeptember 1989

TR 89-22Diffusion of Am, Pu, U, Np, Cs, I and Tc incompacted sand-bentonite mixtureDepartment of Nuclear Chemistry, Chalmers Univer-sity of Technology, Gothenburg, SwedenAugust 1989

TR 89-23Deep ground water microbiology inSwedish granitic rock and it's relevancefor radionuclide migration from aSwedish high level nuclear waste repo-sitoryKarsten PedersenUniversity of Göteborg, Department of Marinemicrobiology, Gothenburg, SwedenMarch 1989

TR 89-24Some notes on diffusion of radionuclidesthrough compacted claysTrygve E EriksenRoyal Institute of Technology, Department ofNuclear Chemistry, Stockholm, SwedenMay 1989

TR 89-25Radionuclide sorption on crushed andintact granitic rockVolume and surface effectsTrygve E Eriksen, Birgitta LocklundRoyal Institute of Technology, Department ofNuclear Chemistry, Stockholm, SwedenMay 1989

TR 89-26Performance and safety analysis ofWP-Cave conceptKristina Skagius1, Christer Svemar2

1 Kemakta Konsult AB2 Swedish Nuclear Fuel and Waste Management CoAugust 1989

TR-89-27Post-excavation analysis of a revisedhydraulic model of the Room 209 fracture,URL, Manitoba, CanadaA part of the joint AECL/SKB characte-rization of the 240 m level at the URL,Manitoba, CanadaAnders Winberg1, Tin Chan2, Peter Griffiths2,Blair Nakka2

1 Swedish Geological Co, Gothenburg, Sweden2 Computations & Analysis Section, Applied

GeoscienceBranch, Atomic Energy of Canada Limited,Pinawa, Manitoba, Canada

October 1989

ISSM)2X4-J7i7

CM Tryrh AB, Bromma 19II9