Transcript
Mühendislik Bilimlerinde Özel
Konular
MUBİ9035 - Mühendislik Bilimleri Bölümüİstanbul Üniversitesi
A FR IC A N P LA TE
8
B LACK SEA
3
1
24
9
8 7
6 5
13 12
11 10
15 14
1617
18
19
20
21
24
M >2.9h< 39km1981-1988
Shear ZoneExtensional ZoneCom pressional ZoneGPS control points
23 24 25 26 27 28 29 30 3133
34
35
36
37
38
39
40
41
42
43
Mw 6.4 1995
Mw 5.8 1997
Mw 6.6 1982
Mw 6.6 1983
Mw 6.8 1981
Mw 6.2 1996
Mw 5.6 1996
25
Mw 5.5 1994
22
23
23 24 25 26 27 28 29 30 3133
34
35
36
37
38
39
40
41
42
43
23
8 7
6
12
11
15
17
18
19
20
21
24
25
23
22
23
1
4
9
13
5
10
14
16
0 20
40
60
80
100
120
140
160
180
200
220
240
260
280
Shear Strain
nstrain/a
23 24 25 26 27 28 29 30 3133
34
35
36
37
38
39
40
41
42
43
-70
-60
-50
-40
-30
-20
-10
0 10 20 30 40 50 60 70 80 90 100
110
8 7
6
12
11
15
17
18
19
20
21
24
Compr. Extens.
nstrain/a
25
23
22
23
1
4
9
13
5
10
14
16
Contour maps of GPS derived shear and dilatation are shown in the maps above (middle and right maps, respectively). GPS strains were derived by Kahle et al. (2000) from GPS velocity data presented by McCloskey et al. (2000) for the western Turkey and eastern Mediterranean area examined in this paper. Average shear and dilatation in each seismic zone were estimated by averaging contour values of shear and dilatation observed on the regular grid of points highlighted in the map above.
GPS control points are shown along with events of magnitude M>3.0 recorded between 1981 and 1998. The 25 seismic zones into which the area was subdivided for analysis and comparison are also outlined.
Geodetical strain and earthquake hazard:
Example from western Turkey
A FR IC AN PLA TE
8
BLA CK SEA
3
1
24
9
8 7
6 5
13 12
11 10
15 14
1617
18
19
20
21
24
M >2.9h< 39km1981-1988
Shear ZoneExtensional ZoneCom pressional ZoneGPS control points
23 24 25 26 27 28 29 30 3133
34
35
36
37
38
39
40
41
42
43
Mw 6.4 1995
Mw 5.8 1997
Mw 6.6 1982
Mw 6.6 1983
Mw 6.8 1981
Mw 6.2 1996
Mw 5.6 1996
25
Mw 5.5 1994
22
23
D2 D15 D2 D15 D2 D15 b ML-MU
Shear
Dilitation1 1.44 1.1 1.73 1.22 1.4 1.01 1.51 2.6-5.0 161.79 19.38
2 1.43 1.07 1.81 1.33 1.43 1.12 1.39 2.6-5.5 201.07 3.633 1.62 1.42 1.9 1.28 1.49 1.26 1.47 3.1-4.8 164.82 12.884 1.24 0.84 1.86 1.5 1.02 0.64 1.11 3.5-6.0 191.60 25.857 1.53 1.24 1.94 1.48 1.48 1.23 1.24 3.2-6.0 101.71 55.878 1.32 0.86 1.85 1.13 1.37 0.92 1.16 3.2-4.9 189.45 3.889 1.18 0.83 1.86 1.4 1.14 0.64 0.97 3.0-5.3 146.38 11.555 1.07 0.73 1.85 1.59 0.95 0.57 1.75 2.6-4.7 41.02 36.216 1.33 0.92 1.81 1.56 1.22 0.78 1.81 2.7-4.8 78.75 33.68
10 0.89 0.58 1.46 0.95 0.87 0.46 1.35 3.0-4.8 70.32 44.6911 1.48 1.2 1.83 1.37 1.53 1.24 1.39 3.0-5.8 102.35 40.9612 1.52 1.26 1.89 1.37 1.53 1.39 1.5 3.2-5.1 72.75 75.8313 1.36 1 1.86 1.71 0.75 0.41 1.1 3.1-5.5 89.26 25.5114 1.4 1.08 1.79 1.26 1.4 1.19 1.32 2.9-5.5 78.81 53.6615 1.57 1.26 1.93 1.36 1.59 1.31 1.28 3.1-5.4 78.25 54.3916 1.38 0.99 1.42 0.97 1.24 0.94 1.4 3.1-5.4 47.99 38.1217 1.42 1.05 1.78 1.44 1.37 1 1.22 3.2-5.4 50.59 37.2218 1.61 1.32 1.9 0.81 1.64 1.43 1.25 3.6-4.9 58.89 80.9119 1.43 1.18 1.88 1.16 1.2 0.88 0.67 3.5-5.2 38.75 22.0920 1.74 1.5 1.81 1.04 1.77 1.64 1.44 3.5-5.3 68.88 20.7621 1.44 1.09 1.79 1.51 0.92 0.55 1.21 3.7-5.0 95.04 18.2722 1.68 1.38 1.87 1.12 1.63 1.39 1.49 3.2-4.6 54.22 10.2123 1.63 1.04 1.82 1.27 1.61 0.99 1.24 3.8-5.7 107.79 -22.8724 1.65 1.23 1.57 0.93 1.75 1.47 1.08 3.7-5.5 103.39 -40.3925 1.45 1.09 2 1.07 1.55 1.08 1.21 3.5-5.8 75.28 -16.12
The study area was divided into three regional tectonic subdivisions consisting of a region of shear in the north associated with the Northern Anatolian Fault Zone (NAFZ), a region dominated by extension in the back-arc region of central Turkey, and a region of compression along the Aegean subduction zone. Seismotectonic parameters (Dq and b) and geodetic strains (shear and dilatation) are shown in the table at right for each of the 25 seismic zones.
Local Variations of Complex Variables
D2 D15 D2 D15 D2 D15 b Shear Dilitation
1.43/1.39 1.07/1.05 1.86/1.85 1.33/1.33 1.4/1.33 1.01/0.97 1.24/1.26 164.8/165.3 12.88/19
1.41/1.37 1.06/1.05 1.84/1.78 1.36/1.29 1.3/1.27 0.97/0.97 1.34/1.34 71.54/67.3 39.5/45.3
1.64/1.6 1.16/1.22 1.82/1.81 1.1/1.16 1.62/1.54 1.24/1.19 1.23/1.28 85.16/84.1 -3/-5
Median/mean values of multifractal correlation dimensions D2 and D15 are tabulated for the full range, 2 to 10km range and 10 to 40 km range for each tectonic subdivision of the study area (shear, extension, and compression). The median/mean values of b, shear, and dilatation are also listed for each tectonic region.
Over the full range: D2 measured in the region of compression is statistically greater than D2 in the regions of extension and shear. D15 is less than D2 in all cases.
Over the 2-10 km scale: Statistically significant differences between regions are not observed.
Over the 10-40km scale: The larger value of D in the region of compression suggests that differences observed over the full range are primarily associated with variations occurring at larger 10-40km scales.
Regional comparison between seismicity and GPS strain
The correlation coefficient, r = 0.81
The probability (p) that the slope of the regression line could actually be zero is 0.026 in this case.
D1.1 1.2 1.3 1.4 1.5 1.6 1.7
b
0.7
0.9
1.1
1.3
1.5
1.7
95% confidence band
Cross-plot of b values and D2 from the Northern Anatolian Fault Zone
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.97 0.81 -0.29 0.28 0.5 -0.39 -0.49 0.49 0.96 0.74 -0.26 0.08D15 0 0.75 -0.38 0.31 0.25 -0.4 -0.39 0.65 0 0.77 -0.28 0.23b 0.03 0.05 -0.1 -0.06 0.39 0.37 -0.1 -0.06 0.06 0.05 -0.1 -0.06Shear 0.52 0.4 0.83 -0.79 0.26 0.39 0.83 -0.79 0.57 0.54 0.83 -0.79Dilat 0.55 0.5 0.9 0.03 0.26 0.12 0.9 0.03 0.86 0.63 0.9 0.03
•Over the full range: A significant positive correlation is observed between seismic clustering (D) and the Gutenberg-Richter b value along the NAFZ strike slip zone.
•Over the 10 -40 km scale: A nearly significant relationship between b and D is observed (r = 0.74, p = 0.06) and suggests that the relationship is primarily associated with deeper or regional scale seismicity since significant correlation is not observed over the 2 to 10 km scale.
•No correlation was observed between seismicity ( b, D2, D15) and GPS strain.
Correlation between seismicity and GPS strain
PositiveCorrelation
NegativeCorrelation
Low-magnitude events(Preshocks)
Large-magnitude events
Afterthoughts on the Izmit Earthquake
Increased b and decreased DC suggest that the rise in the level of low magnitude seismicity and high intensity clustering along the western portion of NAFZ did not completely release stress transferred into this segment of the fault zone (Oncel et al., 1995, Non.Lineer.Geophysics; Oncel and Wilson, 2001, BSSA).
This combination of factors - westward migration along with increased levels of low magnitude
seismicity and higher intensity seismic clustering - are indicators of increased seismic risk in the area.
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.98 -0.29 0.18 0.4 0.48 -0.13 0.18 0.2 0.98 0 0.13 0.67D15 0 -0.38 0.18 0.46 0.12 0.28 0.31 -0.44 0 -0.05 0.15 0.73b 0.36 0.23 0.18 0.21 0.69 0.38 0.18 0.21 1 0.88 0.18 0.21Shear 0.57 0.59 0.57 0.13 0.57 0.34 0.57 0.13 0.68 0.65 0.57 0.13Dilat 0.19 0.13 0.51 0.67 0.54 0.15 0.51 0.67 0.02 0.01 0.51 0.67
•Over the 2-10 km scale: Significant correlation is not observed between seismic clustering and dilatation.
•Over the full range: Significant correlation between b and D is not observed.
•Over the 10 -40 km scale: In this subdivision, seismic clustering (D2 and D15) correlate positively with dilatation (r = 0.67 and 0.73 with p = 0.02 and 0.01 respectively). The correlations suggest that increased rates of extension produce increasingly dispersed seismicity.
Correlation between seismicity and GPS strain
D2 D15 b Shear Dilat D2 D15 b Shear Dilat D2 D15 b Shear DilatD2 0.76 0.51 -0.25 0.03 0.21 0.44 -0.54 0.38 0.9 0.22 -0.22 -0.41D15 0.08 0.71 -0.68 0.47 0.69 -0.02 0.26 0.46 0.01 0.39 -0.44 -0.1b 0.3 0.12 -0.83 0.73 0.38 0.97 -0.83 0.73 0.68 0.45 -0.83 0.73Shear 0.64 0.14 0.04 -0.6 0.26 0.62 0.04 -0.6 0.68 0.39 0.04 -0.6Dilat 0.96 0.34 0.1 0.21 0.46 0.37 0.1 0.21 0.43 0.84 0.1 0.21
•One would expect seismicity to correlate moreso with dilatation in a subduction zone. However, dilatation along the subduction zone is on average only slightly negative. •Dilatation is positive in the areas to the northeast (17 nstrain/a) and negative (-29 nstrain/a) farther west along the subduction zone. This combination of positive and negative dilatation along the subduction zone is probably responsible for the lack of a more significant correlation between b and dilatation. •The change of dilatation from positive to negative as one goes east to west along the subduction zone suggests a transition in plate interaction from transtensional to transpressive.
•Over the full range: Variations of b value correlate negatively with shear (r = -0.83, p = 0.04) in the zones of this subdivision. The correlation of b to dilatation is weakly positive (r = 0.73, p = 0.1).
Correlation between seismicity and GPS strain
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