Kinematic Rupture Process of Manyas (Mw=4.7) and Gemlik (Mw=4.8) Earthquakes Occurred in The Southern Marmara Region

Öz

Source characterization and slip history were estimated for two moderate-sized earthquakes which occurred on the southern branch of the North Anatolian Fault zone (NAFz): October 20, 2006 (Mw 4.7) Manyas Earthquake and October 24, 2006 (Mw 4.8) Gulf of Gemlik Earthquake. These events are the largest to have occurred in the last 20 years on the southern branch of the NAFz. Multi time-window linear waveform inversion technique (MTWIT) was applied to strong ground motion (SGM) data. Theoretical Green’s functions between subfaults and stations were calculated by a Discrete Wave Number Method (DWNM) using one-dimensional (1-D) velocity structure. The inversion technique used in this study yields a non-unique solution. Therefore, various rupture models were tested until a satisfactory match was obtained between observed and synthetic data. Results showed simple patterns in slip distributions. Max. slips are 0.18 m and 0.12 m and seismic moments are 3.43E+15 Nm and 1.73E+15 Nm for the Gemlik and Manyas Earthquakes, respectively. Results were compared with those of similar sized earthquakes around the world and a new empirical relationship was proposed between seismic moment and rupture area. It was aimed at providing useful information for resolving rupture mechanisms and triggering of the events in Southern Marmara region through the findings of the present study.

Anahtar Kelimeler

• Marmara,Earthquake,Kinematic Analysis,Inversion

Güney Marmara Bölgesi’nde Meydana Gelen Manyas (Mw=4.7) ve Gemlik (Mw=4.8) Depremlerinin Kinematik Analizi

Öz

Kuzey Anadolu Fay zonu (KAFz) güney kolunda meydana gelen orta büyüklükte 2 deprem için sismik kaynak karakteri ve faylanmalara ait kaymanın gelişimi incelenmiştir. Bu iki depremden biri 20 Ekim 2006 tarihinde meydana gelen Manyas depremi (Mw=4.7) ve diğeri de 24 Ekim 2006 tarihinde olan Gemlik Körfezi depremi (Mw=4.8) olarak analiz edilmiştir. Her iki depremde, KAFz güney kolundaki son 20 yılda meydana gelen orta büyüklükteki yırtılmalardır. Sayısal analizde kuvvetli yer hareketi (KYH) verisine çoklu zaman-pencereli dalga şekli ters çözümü tekniği uygulanmıştır. Alt fay grupları (tali faylar) ve istasyonlar arasındaki kuramsal Green fonksiyonları bir-boyutlu (1-B) hız yapısı kullanılarak ayrık dalga sayısı yöntemi ile hesaplanmıştır. Bu çalışmada kullanılan ters çözüm tekniği, tekil olmayan çözümü getirmektedir. Bu nedenle hem gözlemsel hem de sentetik veri eşleşene kadar çeşitli yırtılma modelleri denenmiştir. Sonuçlar, kayma dağılımlarında basit modellerine işaret etmektedir. Gemlik ve Manyas depremleri için kayma miktarları sırası ile 0.18m ve 0.12m, sismik moment değerleri ise 3.43E+15 Nm ve 1.73E+15Nm olarak elde edilmiştir.  Sonuçlar, küresel ölçekte benzer büyüklükte depremlerle karşılaştırılmış ve sismik moment ile yırtılma arasında yeni bir deneysel ilişki önerilmiştir. Bulguların Güney Marmara bölgesindeki yırtılma mekanizmalarının çözümlenmesinde ve depremlerin tetiklenmesi için yararlı bilgiler sağlamasını amaçlanmıştır.

Anahtar Kelimeler

• Marmara,Deprem,Kinematik Analiz,Ters Çözüm

Kaynakça

1. Abdel-Fattah A., (2002), Source characteristics of a moderate earthquake (M 4.9) using empirical Green’s function technique, Annals of Geophysics, 45(5), 575-585.
2. Akaike H., Bernardo J.M., (Ed.), (1980), Likelihood and the Bayes procedure, in Bayesian Statistics, Univ. Press, Valencia, Spain. 142-166.
3. Ambraseys N.N., (2002), The seismic activity of the Marmara Sea region over the last 2000 years, Bulletin of Seismological Society of America, 92 (1), 1–18.
4. Armijo R., 22 co-authors, (2005), Submarine fault scarps in the Sea of Marmara pullapart (North Anatolian Fault): implications for seismic hazard in Istanbul, Geochemistry Geophysics Geosystem, 6(6), 1-29, doi:10.1029/2004GC000896.
5. Barka A., (1992), The North Anatolian Fault Zone, Annales Tectonicae, 6, 164-195.
6. Barka A.A., (1996). Slip distribution along the North Anatolian Fault associated with the large earthquakes of the period 1939 to 1967, Bulletin of Seismological Society of America, 86, 1238-1254.
7. Bekler T., Gürbüz C., (2008), Insight into the Crustal Structure of the Eastern Marmara Region, NW Turkey, Pure and Applied Geophysics, 165, 295-309.
8. Bekler F.N., Ozel N.M., Birgöre G., (2009), Rupture Characteristics of The Two Moderate Size Earthquakes on Southern Marmara, Turkey, AGU 2009 Fall Meeting, San-Francisco, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract S31A-1694.

9. Bekler F.N., Ozel N.M., Birgöre G., (2011), Rupture Process of Two Moderate Size Earthquakes in The Southern Marmara Region, AGU 2011 Fall Meeting, San-Francisco, Abstract S43C-2286.
10. Birgören G., Sekiguchi H., Irikura K., (2004), Rupture model of the 1999 Duzce, Turkey, earthquake deduced from high and low frequency strong ground motion data, Geophysical Research Letters, 31, L05610.
11. Bouchon M., (1981), A simple method to calculate Green’s function forelastic layered media, Bulletin of Seismological Society of America,71, 959– 971.
12. Bozkurt E., (2001), Neotectonics of Turkey−a synthesis, Geodinamica Acta, 14, 3-30.
13. Dziewonski A.M., Anderson D.L., (1981), Preliminary Reference Earth model, Phys. Earth Planet. Inter., 25, 297–356.
14. Flerit F., Armijo R., King G.C.P., Meyer B., Barka A., (2003), Slip partitioning in the Sea of Marmara pull-apart determined from GPS velocity vectors, Geophysical Journal International 154, 1–7.
15. Fukahata Y., Yagi Y., Matsu'ura M., (2003), Waveform inversion for seismic source processes using ABIC with two sorts of prior constraints: Comparison between proper and improper formulations, Geophysical Research Letter, 30(6), doi:10.1029/2002GL016 293.
16. Geller R. J., Takeuchi N., (1995), A new method for computing highly accurate DSM synthetic seismograms, Geophysical Jornal International, 123, 449–470.
17. Gürbüz C., Aktar M., Eyidoğan H., Cisternas A., Haessler H., BarkaA., Ergin M., Türkelli N., Polat O., Üçer B., Kuleli H.S., Barıs Ş., Kaypak B., Bekler T., Zor E., Biçmen F., Yörük A., (2000), The seismotectonics of the Marmara Region (Turkey): Results from a microseismic experiment, Tectonophysics, 316, 1–17.
18. Helmstetter A., Kagan Y., Jackson D., (2005), Importance of small earthquakes for stress transfers and earthquake triggering, Journal of Geophysical Research, 110, B05S08, doi: 10.1029/2004JB003286.
19. Ichinose G. A., Smith K.D., Anderson J.G., (1997), Source parameters of the 15 November 1995 Border Town, Nevada, Earthquake Sequence, Bulletin of Seismological Society of America, 87, 652-667.
20. Irmak T.S., Grosser H., Ozer M.F., Woith H., Baris S., (2007), The October 2006 Gemlik Earthquake (M:5.2), Geophysical Research Abtstract, 9, s10212.
21. Karabulut H., Ozalaybey S., Taymaz T., Aktar M., Selvi O., Kocaoglu A., (2003), A tomographic image of the shallow crustal structure in the Eastern Marmara, Geophysical Research Letters, L018074.
22. Kennett B.L.N, Engdahl E.R., (1991), Traveltimes for global earthquake location and phase identification, Geophysical Journal International, 105, 429–465.
23. Kennett B.L., Kerry N.J., (1979), Seismic waves in a stratified half space, Geophysical Journal Royal Astronomical Society, 57, 557– 583.
24. Marsan D., (2005), The role of small earthquakes in redistributing crustal elastic stress, Geophysical Journal International,163, 141-151.
25. Mohammadioun B., Serva, L., (2001), Stress drop, slip type, earthquake magnitude—and seismic hazard, Bulletin of the Seismological Society of America, 91, 694 – 707.
26. Okay A.I., Kaşlilar-Özcan A., İmren C., Boztepe-Güney A., Demirbağ E., Kuşçu, İ., (2000), Active faults and evolving strike-slip basins in the Marmara Sea, northwest Turkey: a multi-channel reflection study, Tectonophysics, 321, 189–218.
27. Selim H., Tüysüz O., Barka A., (2006), Güney Marmara Bölümünün Neotektoniği, ITU dergisi/d mühendislik, C5, 1, 151-160.
28. Somerville P., Irikura K., Graves R., Sawada S., Wald D., (1999), Characterizing Crustal Earthquake Slip Models for the Prediction of Strong Ground Motion, Bulletin of the Seismological Society of America, 70 (1), 59-80.
29. Sekiguchi H., Irikura K., Iwata T., (2000), Fault geometry in the rupture termination of the 1995 Hyogo-ken Nanbu earthquake, Bulletin of the Seismological Society of America, 90, 117– 133.
30. Şaroğlu F., Emre O., Kuşcu I., (1992), Türkiye’nin Aktif Tektonik Haritası, Maden Tekkik ve Arama Genel Müdürlüğü (MTA), Ankara, Turkey.
31. Şengör, A.M.C., (1979), The North Anatolian transform fault: its age, offset and tectonic significance Journal of the Geological Society, 136 (3), 269–282.
32. Rebollar C. J., Quintanar L., Castro R., Day R., Madrid S.M., Brune J., Astiz J.N., Vernon L.F., (2001), Source Characteristics of a 5.5 Magnitude Earthquake that Occurred in the Transform Fault System of the Delfin Basin in the Gulf of California, Bulletin of the Seismological Society of America, 91, 781-791.
33. Tinti E., Fukuyama E.A., Cocco M., (2005), A kinematic source time function compatible with earthquake Dynamics, Bulletin of the Seismological Society of America, 95, 1211– 1123.
34. Tsukuda E., Herece E., Kuşçu I., (1988), Some geological evidence on activity of the western North Anatolian fault, Geyve, İznik, Gemlik area, ITIT Project 8513, 68-91.
35. Wells D. L., Coppersmith K.J., (1994), New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area and Surface Displacement, Bulletin of the Seismological Society of America, 84, 974-1002.