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

Abstract

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.

Keywords

• Marmara,Earthquake,Kinematic Analysis,Inversion

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

Abstract

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.

Keywords

• Marmara,Deprem,Kinematik Analiz,Ters Çözüm

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