T.R. ISTANBUL METROPOLITAN MUNICIPALTY DEPARTMENT OF EARTHQUAKE RISK MANAGEMENT AND URBAN DEVELOPMENT DIRECTORATE OF EARTHQUAKE AND GROUND ANALYSIS PRODUCTION OF MICROZONATION REPORT AND MAPS EUROPEAN SIDE (SOUTH) GEOLOGICAL – GEOTECHNICAL STUDY REPORT ACCORDING TO THE CONSTRUCTION PLANS AS A RESULT OF SETTLEMENT PURPOSED MICROZONATION WORKS FINAL REPORT (SUMMARY REPORT) OCTOBER 2007 ISTANBUL OYO INTERNATIONAL CORPORATION
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T.R. ISTANBUL METROPOLITAN MUNICIPALTY
DEPARTMENT OF EARTHQUAKE RISK MANAGEMENT AND URBAN DEVELOPMENT DIRECTORATE OF EARTHQUAKE AND GROUND ANALYSIS
PRODUCTION OF MICROZONATION REPORT AND MAPS
EUROPEAN SIDE (SOUTH)
GEOLOGICAL – GEOTECHNICAL STUDY REPORT ACCORDING TO THE CONSTRUCTION PLANS AS A RESULT OF SETTLEMENT
PURPOSED MICROZONATION WORKS
FINAL REPORT (SUMMARY REPORT)
OCTOBER 2007 ISTANBUL
OYO INTERNATIONAL CORPORATION
TABLE OF CONTENTS
1 OBJECTIVE AND SCOPE …………………………………………………………… 1 1.1 Objective of the Work ……………………………..………………………………… 1 1.2 Scope of the Work …………………………………………………………………… 1
1.3 Work Organization …………………………………………………………….......... 2
2 INTRODUCTION OF THE WORK AREA AND WORKING METHODS………… 3 2.1 Location of the Work Area ………………………………………………………… 3
2.2 Database, Mapping and Working Methods …………………………………………. 5 2.3 Summary of the Work ..……………………………………………………………. 6
3 GEOGRAPHICAL LOCATION AND GEOMORPHOLOGY…………………….. 7
5 GEOLOGY…………………………………………………………….…………..…... 10 5.1 General Geology ………………………..……........................................................... 10 5.2 Geology of the Project Area……................................................................................ 13
10 ASSESSMENT OF SUITABILITY FOR SETTLEMENT ………………….…….... 78 10.1 Technical and Legal Criteria of the Evaluation …………….………………….……. 78 10.2 Evaluation of Hazards in Terms of Settlement Suitability………………….……….. 78
10.3 Suitable Areas (UA) …………………………………………………..……….......... 78 10.4 Precautionary Areas (ÖA) …………………………………………………………… 79
10.5 Unsuitable Areas (UOA) …………………………………………………………….. 82
11 RESULTS AND SUGGESTIONS ………………….…………………………….….... 84
1
1 OBJECTIVE AND SCOPE
This Report describes the summary of contents, methods and results of “PRODUCTION OF
MICROZONATION REPORT AND MAPS – EUROPEAN SIDE (SOUTH)” (hereinafter referred to as “the
Work”), prepared by OYO International Corporation (OIC), and submitted to Istanbul Metropolitan
Municipality (IMM).
1.1 Objective of the Work
The objective of the Work is to identify separate areas which have different potentials for hazardous
earthquake effects and to produce the seismic microzonation report and maps which can serve as the basis for
“hazard-related land use management and city planning” within the boundary of Istanbul Metropolitan
Municipality. In order to assess these earthquake effects, detailed geological, geophysical, geotechnical, and
seismological investigations and study were conducted.
1.2 Scope of the Work
The flow of whole Work is shown in Fig. 1.2.1.
Fig. 1.2.1 Flow of the Work
(1) Planning and Organization for the Work
(2) Site Investigations and Data Collections
(3) Data Input and Evaluation
(4) Data Analysis and Processing
(5) Microzonation Mapping and Reporting
2
1.3 Work Organization The Work organization is shown in Fig. 1.3.1.
Fig. 1.3.1 Work organization
Istanbul Metropolitan Municipality
Department of
Earthquake and Soil Research
Technical
Committee
OYO International
Corporation
Project Manager
Geological
and
Geotechnical
Work group
Seismological
and
Geophysical
Work Group
City Planning,
Geomorphology,
and GIS
Work Group
Microzonation
Evaluation
Work Group
Project Team
3
2 INTRODUNTION OF THE WORK AREA AND WORKING METHODS
2.1 Location of the Work Area The location of the Work area is shown in Fig. 2.1.1.
Fig. 2.1.1 Location of the Work area
Fig. 2.1.1 Location of the Work area
The Work area, shown in Fig. 2.1.2, is the land portion surrounded with the following coordinates:
ARC 40.8236 29.3607 Kocaeli 1999.8.17 7.4 13.5km EW 0.149g 523m/sGBZ 40.82 29.44 Kocaeli 1999.8.17 7.4 10.9km NS 0.244g 792m/s
Source: PEER Strong Motion Database
44
1062NS
-0.2
-0.1
0
0.1
0.2
0 5 10 15 20 25 30 35 40 45Acc.
(g)
ARC
-0.2
-0.1
0
0.1
0.2
0 5 10 15 20 25 30 35Acc.
(g)
GBZ
-0.3
-0.15
0
0.15
0.3
0 5 10 15 20 25 30Acc.
(g)
Fig. 8.2.2.2 Used Input Waves for Response Analysis
8.2.2.2 Earthquake Ground Motion The earthquake ground motion was evaluated by response analysis and valley/basin correction. The PGA
distribution at ground surface is shown in Fig. 8.2.2.3.
Fig. 8.2.2.3 PGA distribution at ground surface including valley/basin correction
45
8.2.3 Zonation Related to the Surface Ground Motion 8.2.3.1 Zonation with respect to the Average Spectral Acceleration Fig. 8.2.3.1 shows the zonation of the average spectral acceleration (Ssi), which uses the criteria shown in
Table 8.2.3.1.
Table 8.2.3.1 Criteria of Zonation by Average Spectral Acceleration
Zone Criteria
As Ssi ≥ 1.4g
Bs 1.4g > Ssi ≥ 1.2g
Cs 1.2g > Ssi ≥ 1.0g
Ds 1.0g > Ssi ≥ 0.8g
Es 0.8g > Ssi
Fig. 8.2.3.1 Zonation with respect to the Average Spectral Acceleration
8.2.3.2 Zonation with respect to the Short Period Spectral Acceleration The short period (T=0.2 sec) spectral acceleration at ground surface was calculated after Borcherdt (1994).
Fig. 8.2.3.2 shows the zonation of the short period spectral acceleration (Svi), which uses the criteria shown
in Table 8.2.3.2.
46
Table 8.2.3.2 Criteria of Zonation by Spectral Amplification
Zone Criteria
Av Svi ≥ 1.2g
Bv 1.2g > Svi ≥ 1.0g
Cv 1.0g > Svi ≥ 0.8g
Dv 0.8g > Svi ≥ 0.6g
Ev 0.6g > Svi
Fig. 8.2.3.2 Zonation with respect to the Short Period Spectral Acceleration by Borcherdt (1994)
8.2.3.3 Zonation with Respect to the Ground Shaking Hazard
Remark
The zoning map by this methodology was intended to raise the awareness that the place of good
ground condition in general meaning is not always safe for the mid-rise RC frame with brick wall
residential apartments, which are very common in Istanbul. Please don’t misunderstand that the
“bad” ground condition is safe for buildings.
Fig. 8.2.2.4 and Fig. 8.2.3.1 should be used as the total seismic hazard maps.
47
The ground intensity shaking map was produced from two zonation results. A zone was assigned at each
grid by overlaying of “Zonation with respect to the Average Spectral Acceleration (As to Es)” and “Zonation
with respect to the Short Period Spectral Acceleration (Av to Ev)” following Table 8.2.3.3. Fig. 8.2.3.3 shows
the zonation with respect to the ground shaking hazard.
Table 8.2.3.3 Criteria of Zonation by Ground Shaking Hazard
Zonation with respect to the Average Spectral Acceleration As Bs Cs Ds Es
Av AGS AGS BGS BGS CGS
Bv AGS BGS BGS CGS DGS
Cv BGS BGS CGS DGS DGS
Dv BGS CGS DGS DGS EGS
Zon
atio
n w
ith r
espe
ct to
the
Shor
t Per
iod
Spec
tral
A
ccel
erat
ion
Ev CGS DGS DGS EGS EGS
Fig. 8.2.3.3 Zonation with respect to the Ground Shaking Hazard
48
8.3 Liquefaction Hazard Analysis In order to evaluate the liquefaction susceptibility of soils in the project area, the cyclic stress ratio (CSR)
caused by the ground motion due to the expected earthquake and the cyclic resistance ratio (CRR) of the soils
were compared. The overview of the procedure for the liquefaction hazard analysis are shown Fig. 8.3.1.
Fig. 8.3.1 Flow for Evaluation of Liquefaction Susceptibility
Geological Investigations
- Drilling for each grid (Depth:30m)
- SPT (every 1.5m), Laboratory Test
Selection of
Liquefaction Potential Areas
Extra Investigations
- Drilling, SPT, CPT, Labo. Test
Evaluation of Liquefaction Susceptibility
Result of SPT Result of CPT
Fs
PL
Liquefaction Hazard Map
AL
(High)
BL
(Medium)
CL
(Low)
(No Potential)
No potential
Any potential
49
8.3.1 Calculation for Liquefaction Susceptibility The calculations of liquefaction susceptibility were conducted by two methods, one using SPT
results and the other using CPT results. These calculation flows are shown in Fig. 8.3.1.1 and Fig. 8.3.1.2 respectively.
Fig. 8.3.1.1 Calculation for Liquefaction Susceptibility by SPT Data
Fig. 8.3.1.2 Calculations for Liquefaction Susceptibility by CPT Data
51
After calculating the liquefaction susceptibility, three zones were defined as Table 8.3.1.1.
Table 8.3.1.1 Zonation by Liquefaction Hazard
Zone Criteria Description
AL PL > 15 High susceptibility
BL 5 ≤ PL ≤ 15 Medium susceptibility
CL PL <5 Low susceptibility
8.3.2 Evaluation of Liquefaction Hazard
The Liquefaction Hazard Map was produced as shown in Fig.8.3.2.1. The following results are derived in
terms of the liquefaction susceptibility.
a) AL, “high liquefaction susceptibility” zones are typically observed at the following areas;
- The southern sand bank and the east bank of the Küçükçekmece Lake
- A part of the alluvium deposit area at the west part of the Lake
- A part of the alluvium deposit area along the Ayamama River
- The coastal areas to the Marmara Sea from Bakırköy to Eminönü
- A part of the west bank of the Golden Horn
b) BL, “medium susceptibility “ zones or CL, “low susceptibility” zones are typically observed at the
following areas;
- The west part of the Lake
- The westernmost part of the project area
- The most of alluvium deposit areas in the middle part of the project area
c) The high – medium susceptibility zones are generally observed in the alluvium or fill deposit areas. In
case the tertiary deposits consist of sands or silty-sands with high groundwater level, these soils rarely
have the liquefaction susceptibility.
d) In general, the high susceptibility zones exist very locally except the southern sand bank and the east
bank of the Küçükçekmece Lake.
52
Fig. 8.3.2.1 Liquefaction Hazard Map
53
8.4 Mass Movements (Slope Instability) 8.4.1 Method for the Landslide Hazard Analysis
8.4.1.1 Evaluation of the Present Landslide Activities The categorized landslides area shown in Table 8.4.1.1.
Table 8.4.1.1 Proposed evaluation for the present activity of landslides
Activity Damages of buildings, topographic features
Activity I - Very clear landslide morphology
- There are two or more damages with displacement of 10 cm or more.
Furthermore, lots of other damages are observed.
- It is inferred that these landslides will move by 1 – 10cm per year.
Activity II - Clear landslide morphology
- There are two or more damages with displacement of 1 - 10 cm.
- It is inferred that these landslides will move by 1 cm or less per year.
Activity III - Not clear landslide morphology
- Lots of damages possibly caused by landslides are observed.
- These landslides seem to be slightly active or the slopes are instable.
Activity IV - Not clear landslide morphology
- Some damages possibly caused by landslides are observed.
- These landslides seem to be slightly active or the slopes are instable.
Activity V - Not clear landslide morphology
- Some damages possibly caused by landslides are observed.
- These landslides seem to be slightly active.
8.4.1.2 Shear Strength of Soils by Shear Box Test The shear box tests were conducted using UD and SPT samples in the landslide areas. These samples
consist of the Gungoren clay or Gurpinar clay at the depth of 7m – 10m.
Table 8.4.1.2 shows the shear resistance angle for each landslide activity.
Table 8.4.1.2 Shear Resistance Angle for Each Landslide Activity
Activity Rank Ⅰ Ⅱ Ⅲ Ⅳ Ⅴ
Shear Strength Angle (degree) 5 7 10 15 20
54
8.4.1.3 Examination of Estimation of the Shear Resistance Angle The relation of the safety factor, the slope inclination of the landslide, and the strength of the slip surface is
shown in the following formula (1) and the chart (Fig. 8.4.1.1), by Siyahi and Ansal (1999).
Using this formula, the strength of the slip surface for the present situation can be estimated by
back-calculation using the safety factor of each landslide block, where pga(g) is peak ground acceleration
during earthquake and “pga=0” implies non-earthquake situation.
N1(pga): minimum stability number according to pga ( coefficient given with the
following chart)
Fig. 8.4.1.1 Relation of the slope inclination of the landslide, and the strength of the slip surface
The present safety factor (without earthquake) can be calculated by applying pga=0 to the previous formula
(1). Fig. 8.4.1.2 shows the present safety factor for each landslide activity.
55
Safety Factor at Present
0
1
2
3
4
5
6
7
0 5 10 15 20
Inclination of Landslide
Safe
ty F
act
or Activity Ⅰ
Activity Ⅱ
Activity Ⅲ
Activity Ⅳ
Activity Ⅴ
Fig. 8.4.1.2 Present Safety Factor for Each Landslide Activity
According to the result, the safety factors of landslides with the highest activity are 1.0 – 1.2. These values
are reasonable considering that these landslides are unstable at present causing some damage to buildings. The
low active landslides show considerably high safety factors. The estimated shear resistance angles can be
judged proper as a whole.
8.4.1.4 Calculation of the Safety Factor at the Earthquake The safety factor at the earthquake can be calculated using the previous formula (1). This formula is based
on a laboratory test using the Caolin (clay with low plasticity), of which the soil strength will become fairly
lower due to earthquakes. Ordinary clayey soils generally have higher plasticity. That means the formula (1)
represents the most dangerous case.
Taking the above consideration into account, it will be an overestimation if the PGA value itself is used for
the formula (1). In general, around 30% of the peak ground motion (PGA) is used for the effective ground
motion for grounds or buildings. Therefore, 30 % of PGA is used as the ground motion for the formula (1).
8.4.2 Evaluation of the Landslide Hazard The evaluation by the safety factor at the earthquake is the relative one based on the presumption of the
present safety factor and the decrease of PGA.
Of the landslides in the project area, there are ones with clear landslide morphology and ones with not clear
morphology. The landslides with clear morphology have possibly moved every time the big earthquake occurs,
56
while the landslides with not clear morphology have not moved for more than 1,000 years.
Therefore, a landslide which has the same safety factor as the ones with clear landslide morphology is
expected to move at the next big earthquake. On the other hand, a landslide which has the same safety factor as
the ones with not clear landslide morphology is not expected at the next big earthquake.
Fig. 8.4.2.1 shows the relation of the extent of development of the landslide morphology and the safety
factor at the earthquake. According to this relation, the safety factor of landslides with clear morphology is less
than 1.0. In case the safety factor is more than 2.0, the landslide hazard risk will be relatively low.
Safety Factor at Earthquake and Landslide Topography
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
0 5 10 15 20
Inclination of Landslide
Saf
ety
Fac
tor
at E
arth
quak
e
Not Clear
Medium
Developed
Fig. 8.4.2.1 Development of landslide topography and safety factor at earthquake
Taking these considerations into account, the landslide hazard risk can be divided into the following three
categories.
Fs ≤ 1.0 ASL (High risk )
1.0< Fs < 2.0 BSL (Medium risk)
Fs ≥ 2.0 CSL (Low risk)
Fig. 8.4.2.2 shows the Landslide Hazard Map.
57
Fig. 8.4.2.2 Landslide Hazard Map
58
9 WATER STATUS
9.1 Ground Water Levels In order to observe water level, 50mm diameter of PVC pipes were inserted into 4364 mechanical
boreholes with different depths (except PS Logging and Deep Wells) just after completion of drilling works.
The top of each borehole was covered by concrete block to maintain the borehole under protection for the
observation.
Water level measurements were done in 2 or 3 days after the completion of boreholes. Water levels in boreholes were observed once a month for a year (as optimum twelve times) from completion of drilling works. Each result were recorded in the prepared forms and digitized.
During the measurements, water level in some boreholes measured higher than other surrounding
boreholes due to remaining drilling water in these boreholes (water couldn’t pomped out efficiently after
completion of drilling). Data collected from these boreholes were used in estimations if the water level
decreased to a similar level with the surrounding borehole water levels in two or three monts time.
Measures that shows major dissonance (very low or very high) to measures of surrounding borehole water
levels, were ignored. Measures in drilling points, which was damaged and not possible to get enough data,
were reflacted to the maps with using geophysical data and correlation of measurement in surrounding
boreholes.
In final table, it was seen that water levels measured in summer time are similar to water levels measured
in winter time. The Highest water level values were used in the maps mantioned above, because
groundwater level is most important factor for espacially liquefaction and landslide analysis. Forms with
whole measurements can be found in CDs attached to this raport. Figure 9.1.1 shows elevation distribution of groundwater tray regarding the sea water level. Averaged
groundwater levels are corresponded to topography so the water level is high on hills while it drops in low
lands. Water level is same or similar to sea water level or contiguous river levels. Figure 9.1.2 showes
grounwater depth contour from surface.
59
Fig. 9.1.1 Groundwater Level Elevation Contour from Average Sea Water Level
60
Fig. 9.1.2 Groundwater level depth contour from surface
61
9.2 Flooding Hazard Analysis The “Flooding Hazard” consists of the following two types of hazard:
a) Flooding along the lower river areas due to a dam break (referred as to ‘Dam Break Model’).
b) Flooding along the river areas due to over-precipitation (referred as to ‘River Flooding Model’).
9.2.1 Analysis Method A finite difference method by the 2D Shallow Water Equation was used for the numerical analysis for the
Flooding Analysis (both of the Dam Break Model and the River Flooding Model)
9.2.2 Analysis Results 9.2.2.1 Dam Break Model There are two areas for the analysis by the Dam Break model as shown in Fig. 9.2.2.1.
Fig. 9.2.2.1 Area for Dam Break Model
Sazlıdere Dam Alibey Dam
62
The maximum flow dapth due to the dam break is shown in Fig.9.2.2.2 for Sazlidere Dam and Fig.9.2.2.3
for Alibey Dam respectively.
Fig. 9.2.2.2 Maximum Depth (Sazlıdere Dam)
Maximum Depth (m)
63
Fig. 9.2.2.3 Maximum Depth (Alibey Dam)
Maximum Depth (m)
64
9.2.2.2 River Flooding Model Total 6 regions were selected for the analysis by the river flooding model as shown in Fig. 9.2.2.4.
Fig. 9.2.2.4 Area for River Flooding Model
Region1 Region 2
Region 3
Region 4
Region 5 Region 6
65
9.2.3 Evaluation of Flooding Hazard Calculated results were evaluated in terms of the hazard assessment. The calculated results include a lot of
‘noise’ and some ‘unrealistic data’. For example, some large flooded areas in the River Flooding Model are
apparently due to the relatively high elevation of bridges (roads or railways) at the lower side. These data was
removed for the hazard mapping.
The evaluated areas were divided into three flooding hazard zones as shown in Table 9.2.3.1. The Flooding
Response Analysis (PGA at slopes by active faults)
Stability Analysis (slip limit PGA for slopes)
Landslide Simulation (movement of slip mass of slopes)
Simple Probability of Tsunami for Istanbul
Active Faults Parameters
Tsunami Simulation
Tsunami Probability Analysis
Tsunami Probability Maps (vulnerable areas at Istanbul Shore)
Submarine Landslides Parameters
(verification)
68
9.3.1 Historical Tsunamis for Istanbul Fig. 9.3.1.1 is the distribution of historical tsunamis in Marmara Sea with space (Altinok, 2006b). Based
on Altinok (2006b) etc. 30 events of historical tsunami during these 20 centuries for Istanbul were identified.
Fig. 9.3.1.1 Historical tsunami in Marmara Sea from 120 to 1999 A.D. with space (Altinok, 2003)
9.3.2 Tsunami Simulation Samples of simulated results for the Princes’ Islands faults are shown in Fig. 9.3.2.1. East side especially
Adalar area of Istanbul city will be affected higher tsunami heights, and most of cases. The arrival time of
initial wave will be within 10 minutes, and the maximum tsunami wave will arrive within 60 to 90 minutes
after the generation of earthquake.
When Princes’ Island fault will move, Istanbul city area will be affected more than other faults of Ganos or
Central Marmara faults. Tsunami height to Adalar will reach 4 to 7 meters, to east side including Kadıköy or
Tuzla will be 3 to 5 meters, and to west side including Yenikapı Yeşilköy or Avcılar will be 3 to 4 meters. But
in Bosphorus and Golden Horn, tsunami height will be maximum 2 meters.
Run-up height (m; height from sea level) is similar to tsunami height along shore, but 30 to 80 % higher
than inundation depth. Thus inundation depth is 50 to 80% of tsunami height along shore.
69
Fig. 9.3.2 1(a) Simulated Results for Princes’ Island Fault
70
Fig. 9.3.2 1(b) Simulated Results for Princes’ Island Fault
71
9.3.3 Simulation Results of Submarine Landslides Samples of simulated results for EN1 of northern slope of Çinarcik Basin are shown in Fig. 9.3.3.1. East
side of Istanbul Municipality especially Adalar area will be affected higher tsunami heights. The arrival time of
initial wave will be within 10 minutes, and the maximum tsunami wave will arrive within 60 to 90 minutes
after the generation of earthquake.
Tsunami heights are maximum 4 to 5 m except West Marmara or ON2 southern Çinarcik Basin cases.
Inundation depths are maximum 3-4 m by EN1, EN3 and ON1 cases. Run-up heights are similar to inundation
depth.
9.3.4 Simulation Results of Combination of Active Faults and Submarine Landslides Fig. 9.3.4.1 shows a sample of the simulation results of combination of active faults and submarine
landslides.
9.3.5 Probability of Tsunami for Istanbul The tsunami wave height at the coast of 10% probability of exceedance for 50 years is shown in Fig.
9.3.5.1. The Asian side of Istanbul is more hazardous than European side. The highest wave height is expected
in Adalar and the highest wave height exceeds 9m. Kartal and Kadıköy are the next hazardous area in Asian
side. In the European side, 3 to 4 m height is expected in Bakırköy to Zeytinburnu.
The tsunami inundation depth at the seaside of 10% probability of exceedance for 50 years is shown in Fig.
9.3.5.2 and Fig. 9.3.5.3. The inundation at the south of Küçükçekmece Lake is remarkable. The maximum
inundation distance from the coast reaches about 600m. The seaside of Kadıköy and Kartal to Tuzla also
expected to suffer run-up for 100 to 300m from the coast.
72
Fig. 9.3.3.1 Simulated Results for EN1(northern Çinarcik Basin)
73
Fig. 9.3.4 1(a) Simulated Results of Active Faults and Landslides
74
Fig. 9.3.4 1(b) Simulated Results of Active Faults and Landslides
10.1 Technical and Legal Criteria of the Evaluation This evaluation of suitability for settlement was prepared according to 15 different Microzonation Maps,
which were produced regarding the technical specifications of this work, include each disaster hazard
evaluation. The Technical Specifications of this work and several standarts, regulations, circulars..etc that
implied in this spesification are technical purpose of the evaluation.
Regulations (by-laws) and circulars issued by the Ministry of Public Works and Settlement (MPWS) were
taken into account as criteria for the preparetion of suitability for settlement maps and reports belonging to
these maps. It was tried to stick to the size implied in circular which 31.05.1989 dated and 4343 numbered (no.
89/16) in this evaluation but, due to Microzonation maps are basis for this study and also this study is intensive
and very detailed, the Manuel for “Integration of Geo-scientific Data to Planning” prepared by the MPWS on
December 2006 was used.
10.2 Evaluation of Hazards in Terms of Settlement Suitability The following hazards were taken into consideration for the assessment of suitability for settlement
Also, precationary areas sub-divided into 2 regions regarding to the variaty and desity of problems and
measures for these problems;
- ÖA(a) : Primary Precautionary Areas
- ÖA(b) : Secondary Precautionar yAreas
10.4.1 Precautionary Areas -1 These are the areas with liquefaction hazard. In case of evaluation of liquefaction hazard in terms of
80
suitability for settlement, each factor should be investigated regarding to damage on buildings or ground. One
of these factors is ground settlement deformation due to liquefaction. Suitability for settlement can be
estimated by ground deformation level.
As a result, precautionary areas in terms of liquefaction hazard were divided into two sub-section as
“ÖA-1(a)” and “ÖA-1(b)”.
10.4.1.1 Precautionary Areas-1(a); ÖA1(a)
These areas are zones which include quaternary aged, grainy and terrestrial based alluvial deposits and sea
- based soft grounds in coasts.
In these areas;
- Liquefaction potential is high,
- Silt, clay and gravel layers are existed ,
- Groundwater is too close to surface, ,
- There is a risk for ground amplification,
- There are infirm (soft) grounds in terms of foundation engineering,
- Groundwater and stability problems may occure in foundation digs.
- 10-30cm of settlements are expected according to analysis results.
- Ground damages like small cracks, sand leakages..etc are expected.
10.4.1.2 Precautionary Areas-1(b); ÖA1(b)
These areas are zones which include quaternary aged, grainy and terrestrial based alluvial deposits and sea
- based soft grounds in coasts.
In these areas,
- Liquefaction potential is low,
- There are layers with clay, silt, sand and gravel.
- Groundwater is close to the surface,
- There is a risk for ground amplification
- There are infirm (soft) grounds in terms of foundation engineering,
- Groundwater and stability problems may occure depending thickness of soft material in foundation digs
- 10-30cm of settlements are expected according to analysis results,
- Ground damages like small cracks..etc are expected.
10.4.2 Precautionary Areas-2
These are the areas with mass movements that may occure in some circumstances (Landslide).
Precautionary areas in terms of mass movements were divided into 2 sub-section as “ÖA-2(a)” and “ÖA-2(b)”
10.4.2.1 Precautionary Areas-2(a): ÖA2(a) These are the areas that include Gürpınar and Güngören members, can be found in high inclination slopes
81
with serious stability problems. Areas with present safety factor estimated as (1.0 < Fs ≤2.0) from conducted
analysis were evaluated in this group.
These areas ;
- Consist of clay, silt and sand under these materials,
- Have inclination that may effect stability negatively,
- Have groundwater problem,
- Have possibility of slip surfaces that effect stability may be deeper than 10m of depth.
10.4.2.2 Precautionary Areas-2(b): ÖA2(b) These are the areas that include Gürpınar and Güngören members, can be found in high inclination slopes
with medium-high stability problems.
These areas,
- Consist of clay, silt and sand under these materials
- Have inclination that may effect stability negatively
- Have groundwater problem
- Slip surfaces that effect stability are between 3-10m of depth
10.4.3. Precautionary Areas-3 These areas have flooding possibility in case of an earthquake. These areas are mostly close to coasts,
valleys intersected with a coastal and Haliç (Golden Horn) connected to sea and lake shores.
These areas are divided into 2 subsections as “ÖA3(a)” and “ÖA3(b) according to possible wave hight.
10.4.3.1. Precautionary Areas-3(a): ÖA3(a) These are areas where the tsunami height or inundation depth is expected to be between 3m ≤ HW <10m.
Actually there is no such zone in the project area.
10.4.3.2 Precautionary Areas-3(b): ÖA3(b) These are areas where the tsunami height or inundation depth is expected to be between 0m < HW < 3m
Because of medium-low flooding hazard, special measures should be taken such as evacuation plans (routes,
places, or notification system). Also, advises should be taken from related departments (ISKI,DSI..etc) for
planning against possible floodings that may occure in valleys or other flood vulnerable areas depending on
participation.
10.4.4 Precautionary Areas-4 and Precautionary Areas-5
These are areas with some engineering problems such as Alluvium areas, artificial fillings, tasman, rock
falls, and cave-in of mines.
These areas were divided into 4 subsections as “ÖA4(a), ÖA4(b), ÖA5(a) and ÖA5(b)“ in terms of
engineering problems and level of the measures to be taken.
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10.4.4.1. Precautionary Areas-4(a): ÖA4(a) These areas have major engineering problems such as very thick alluvium and very thick artificial fillings ,
etc. Actually there is no such zone in the project area.
10.4.4.2. Precautionary AReas-4(b): ÖA4(b)
These areas represented by alluvium and artificial fillings. Thichness and distributions of these artificial
fillings in these areas should be determined before construction because these fillings do not considered as
carrier. Therefore, in construction phase, the foundation of buildings should be put on stable grounds.
10.4.4.3. Precautionart Areas-5(a): ÖA5(a)
These are areas with major engineering problems such as tasman, rock falls, cave-in of mines, etc. Actually
there is no such zone in the project area.
10.4.4.4. Precautionary AReas-5(b): ÖA5(b) These areas represented by rock fall hazard areas, tasman areas and mine areas. These areas includes step
rock slopes, underground karstic gaps in some parts of the study area. Wedge type of slips may occure in rock
environments, deep drillings and steep slopes. Tasman may occure in Bakırkoy region because of karstic gaps.
10.4.5. Precautionary Areas-6 These are areas with multiple problems like liqufaction, flooding, mass movements and engineering
problems. These areas divided into 2 subsections according to levels of problems and measures.
10.4.5.1 Precautionary Area-6(a): ÖA6(a) These areas have more than one of the above problems with one of these problems has 1.level (a) of
importance. Detailed studies should be conducted before implementation and measures to take should be
determined.
10.4.5.2 Precautionary Areas-6(b): ÖA6(b) These areas have more than one of the above problems with one of these problems has 2.level (a) of
importance. Detailed studies should be conducted before implementation and measures to take should be
determined.
10.5 Unsuitable Areas (UOA) Unsuitable Areas (UOA) are defined in Table 10.5.1 with taking previous evaluations of related hazards
into account. This area should not be planned and opened to the settlement due to some high hazard
possibilities in terms of suitability of settlment. Avcılar Ambarlı Balaban District, Denizköşkler Districkt,
Bakırköy Menekşe District, lake slopes in east part of Firuzköy and Halkalı garbage dump area are inside of
this area.
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Table 10.5.1 Definition of “UOA” (Unsuitable Areas)
Area Category Descriptions
UOA
(Unsuitable Area)
Areas which are assigned to the highest hazard and assigned to UOA area for at
least one of the following hazard items:
(1) Liquefaction Hazard (Very soft ground areas like swamp..etc.)
(2) Landslide Hazard
(3) Flooding Hazard
(4) Engineering Problems
These areas were divided into 4 subsections according to source of the problem. There is no area with
Liquefaction hazard (UOA1) or Flooding hazard (UOA3) in Project area. Unsuitable Areas correspond
to %1,42 of Project area.
10.5.1 Unsuitable Areas-2: UOA-2 These areas have active mass movements and determined as active landslide areas in previous studies in
Project area. These areas should not be planned and opened to the settlement.
10.5.2 Unsuitable Areas-4: UOA-4
These areas are thick artificial filling areas in Project area. These areas should not be planned or opened to
settlement because of their thickness of fills and physical-chemical characteristics. Halkalı garbage dumb
should be considered in this group in Project area.
Detailed characteristics of problems and evaluations of analysis that suitability for settlement groups have,
can be found in related section.
Unsuitable areas should not be planned for structuring and parcel-based, detailed Ground Survey Works
should be conducted for every other areas.
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11 RESULTS AND SUGGESTIONS (1) PRODUCTION OF SETTLEMENT PROPOSED MICROZONATION REPORT AND MAPS –
EUROPEAN SIDE (SOUTH)” work which belongs to Istanbul City, European Side (South) was
conducted by OYO International Corporation on behalf of The Istanbul Metropolitan Municipality (IMM).
Geological, geotechnical, geophysical characteristics of the Work area were identified and the data were
analyzed.
(2) Total 16 microzonation hazard maps were produced as implied in technical spesificaiton of this work.
Also, extra 11 contributing and correlation maps were created. As a result of these maps and evaluation of
risks reffered in these maps, 1/2000 scale “Settlement Suitability Maps” were produced.
(3) Total 2830 normal drillings with 30m depth, 27 deep drillings with 80-250m depth, 764 liquefaction
drillings with 20m depth, 608 landslide drillings with 30m depth, 100 drillings with differant depths to
determine baserock depth and thickness of some formations and also 35 drillings to determine some
structural features like faults and alluvium thickness as a total number of 4364 mechanical drillings were
conducted in 2912 grids (250x250) within the context of project and total drilling depth was reached to
125578,90m. Beside SPT tests which were conducted in field, 636 CPT tests were also conducted. 2762
Array Microtremor measurement in 30 points and 20km lenght Seismic Reflection measurement were
conducted within the context of geophysical studies.
(4) Work area is in regions that contain differant earthquake risks according to Turkey Earthquake Regions
Map. Considering strong ground movements contained from last earthquake and accelerations and also
according to Probabilistic Earthquake Hazard Maps preapered in this work and geological-geophysical,
geomorphologic and techtonic charactersitics of the study area, informations about previous earthquakes
and existing earthquake hazard maps should be reviewed and updated.
(5) Active landslides were observed in Menekşe District, Balaban District, slopes of east side of Küçükçekmece Lake (Firuzköy) and Denizköşkler District in Project area These areas were evaluated as unsuitable areas for settlement. There is a 28/06/2005 dated and 9109 numbered Cabinet Decision Disaster Effected for Avcılar Ambarlı District. Rock fall or avalanche risk do not existed in Project area other than this one. Opinion of DSI (ISKI) should be taken for water courses in Project area before planning.
(6) The project area was basically divided into three (3) zones as Suitable Areas (UA), Precautionary
Areas (ÖA) and Unsuitable Areas (UOA) in terms of the settlement suitability;
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Suitable Areas (UA)
In these areas there are zones with Trakya, Ceylan, Gürpınar Formations, units belonging to Bakırköy
Member and units belonging to Güngören Member geologicly.
Precautionary Areas (ÖA)
These areas have items like natural disaster hazards and geologic-geotechnic characteristics that may
effect areas in terms of suitability for settlment so, planning and structuring for these areas is possible
with taking some measures before or during structuring. Precautionary Areas (ÖA) were divided into
sub-titles regarding to the problems that were occured and/or possible to occure. These areas are;
- Precautionary Area 1 (ÖA1) : in terms of Liquefaction Hazard
- Precautionary Area 2 (ÖA2): in terms of Stability Hazard
- Precautionary Area 3 (ÖA3) : in terms of Tsunami and Flooding Hazard
- Precautionary Area 4-5 (ÖA4 - ÖA5) : in terms of Engineering Problems
- Precautionary Area 4 (ÖA4): In terms of Artificial Filling and Alluvium Areas
- Precautionary Area 5 (ÖA5) : In terms of Rock Fall, Tasman Hazard and Mine areas.