the present day stress states in the marmara region

THE PRESENT DAY STRESS STATES IN THE MARMARA REGION

Yasemin KORKUSUZ and Nurcan Meral ÖZEL([email protected])

Boğaziçi UniversityKandilli Observatory and Earthquake Research Institute

Department of Geophysicsİstanbul, TURKEY

Baku - May, 2013

• 2(Reilinger et al., 2010)

The Anatolian Block and The Marmara Region

• 3

Recent Earthquake Activity of the Marmara Region

Eastern Ganos Offshore C.

Eastern TekirdağBasin C.

Çınarcık Basin C.

Yalova C.

Gemlik C.5 Earthquake clustersAnalyzed-600 eqsSelected-398 eqs

• 4

Station Distribution

Total 105 seismic stations

• 5

Selection of visible earthquake clusters

Discrimination of earthquakes in terms of local magnitudes using shell in linux

Earthquakes ML<2.0

Throw out

Earthquakes ML≥2.0

Data merge - reading polarities, and P and S pahases by PQL-II

Number of polarity per earthquake<10

Number of polarity per earthquake≥10

Throw outConverting phase reading file into Nordic format

Relocations by Hypocenter

Source Mechanisms for 1˚ grid search through the program of Focmec

Application of the method of Horiuchi et al. (1995)

Discrimination of fault planes from auxiliary planes

Orientations of three principal stress axes

Souce Mechanisms for 5˚ grid search

The Methodology

• 6

RESULTS

1. Eastern Ganos Offshore ClusterEarthquakes 85 of 144

Earthquakes with SBO data

4

Total polarity

1768

Average polarity

21

Earthquakes with 1 misfit (Horiuchi. et al. 1995)

22

Earthquakes with 1 misfit (Focmec)

3

Average ERDP

2.6 km

Average ERLT

1.0 km

Average ERLN

1.2 km

Average GAP

65˚

• 7

Stress Tensor Inversion Results of the Eastern Ganoss Offshore Cluster

Sigma-1 315-35

Sigma-2 141-50

Sigma-3 221-7

R-value 0.66

• 8

2. Eastern Tekirdağ Basin Cluster

Earthquakes 75 of 105


0

Total polarity

2063

Average polarity

28


28


7

Average ERDP

3.1 km

Average ERLT

1.2 km

Average ERLN

1.4 km

Average GAP

58˚

• 9

Stress Tensor Inversion Results of the Eastern Tekirdağ Basin Cluster

Sigma-1 293-70

Sigma-2 143-30

Sigma-3 30-0

R-value 0.8

• 10

25.07.2011 ML5.2 and 7.06.2012 ML5.1 Marmara Sea earthquakes and Tekirdağ Basin Cluster

25.07.2011 ML5.2Marmara Sea Eq.

07.06.2012 ML5.1Marmara Sea Eq.

E. Tekirdağ Basin C.(2006-2011)

N1-Strike/Dip/Rake 130/63/-63 343/74/-59 -

N2-Strike/Dip/Rake 262/37/-132 98/35/-151 -

P (Trend, Plunge) 83, 62 280, 53 293, 70

T (Trend, Plunge) 201, 14 46, 24 30, 0

• 11

3. Çınarcık Basin ClusterEarthquakes 73 of

116Earthquakes with SBO data

22

Total polarity 1494

Average polarity

20


12


3

Average ERDP 2.8 km

Average ERLT 0.8 km

Average ERLN 1.2 km

Average GAP 64˚

• 12

Stress Tensor Inversion Results of the Çınarcık Basin Cluster

Sigma-1 123-80

Sigma-2 298-10Sigma-3 206-5R-value 0.67

• 13

4. Yalova Cluster



14

Total polarity 2336

Average polarity

23


23


7

Average ERDP 2.5 km

Average ERLT 0.9 km

Average ERLN 1.2 km

Average GAP 55˚

• 14

Stress Tensor Inversion Results of the Yalova Cluster

Sigma-1 285-75

Sigma-2 115-7Sigma-3 201-2R-value 0.32

• 15

5. Gemlik Cluster



10

Total polarity 1565

Average polarity

25


19


11

Average ERDP 3.0 km

Average ERLT 1.1 km

Average ERLN 1.4 km

Average GAP 75˚

• 16

Stress Tensor Inversion Results of the Gemlik Cluster

Sigma-1 90-65

Sigma-2 285-30

Sigma-3 209-12

R-value 0.54

• 17

16.08.2011 (ML 4.0) and 24.10.2006 (ML 5.2) Gemlik Gulf Earthquakes

Quality 16.08.2011 ML4.0 24.10.2006 ML5.2 Gemlik Cluster

P (Trend, Plunge) 297, 59 85, 45 102, 58

T (Trend, Plunge) 33, 3 210, 30 189, 5

B (Trend, Plunge) 125, 31 319, 30 285, 30

N1-Strike/Dip/Rake 329/56/-51 144/81/-60 -

N2-Strike/Dip/Rake 94/50/-133 249/31/-162 -

• 18

ClusterName

Used-All EventsPolarityCounts

Sigma-1Az-Pl

Sigma-2Az-Pl

Sigma-3Az-Pl

RMisfit

Counts

1-Ganos O. 85-144 1768 315-35 141-50 221-7 0.66 22

2-Tekirdağ B. 75-105 2063 293-70 143-30 30-0 0.80 28

3-Çınarcık B. 73-116 1494 123-80 298-10 206-5 0.67 12

4-Yalova 102-125 2336 285-75 115-7 201-2 0.32 23

5-Gemlik 63-100 1565 102-58 285-30 189-5 0.54 19

The present day stress states in the Marmara Region

• 19

CONCLUSION

In this study :

600 eq have been analysed using 105 seismic stations records Time period between 02.09.2006 and 31.03.2011 Criteria: Minimum 10 polarity and maximum 1 misfit Number of earthquakes decreased from 600 to 398 9226 polarity and more than 15.000 P and S phases re-identfied for 398 eq 398 ML≥2.0 earthquakes were relocated Individual focal mechanism solutions and stress tensor orientations have been obtained

25 July 2011 ML5.2 and 7 June 2012 ML5.1 Tekirdağ Basin, and 16 August 2011 ML4.0 Gemlik Gulf earthquakes have been analysed

Average Error Values polarity : 23 ERDP : 2.75 km ERLN : 1.28 km ERLT : 1.0 km GAP : 63˚

• 20

Thank You …

Kandilli, İstanbul

the present day stress states in the marmara region

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