The 2014 Earthquake Model of the Middle East: seismogenic sources

The Earthquake Model of Middle East (EMME) project was carried out between 2010 and 2014 to provide a harmonized seismic hazard assessment without country border limitations. The result covers eleven countries: Afghanistan, Armenia, Azerbaijan, Cyprus, Georgia, Iran, Jordan, Lebanon, Pakistan, Syria and Turkey, which span one of the seismically most active regions on Earth in response to complex interactions between four major tectonic plates i.e. Africa, Arabia, India and Eurasia. Destructive earthquakes with great loss of life and property are frequent within this region, as exemplified by the recent events of Izmit (Turkey, 1999), Bam (Iran, 2003), Kashmir (Pakistan, 2005), Van (Turkey, 2011), and Hindu Kush (Afghanistan, 2015). We summarize multidisciplinary data (seismicity, geology, and tectonics) compiled and used to characterize the spatial and temporal distribution of earthquakes over the investigated region. We describe the development process of the model including the delineation of seismogenic sources and the description of methods and parameters of earthquake recurrence models, all representing the current state of knowledge and practice in seismic hazard assessment. The resulting seismogenic source model includes seismic sources defined by geological evidence and active tectonic findings correlated with measured seismicity patterns. A total of 234 area sources fully cross-border-harmonized are combined with 778 seismically active faults along with background-smoothed seismicity. Recorded seismicity (both historical and instrumental) provides the input to estimate rates of earthquakes for area sources and background seismicity while geologic slip-rates are used to characterize fault-specific earthquake recurrences. Ultimately, alternative models of intrinsic uncertainties of data, procedures and models are considered when used for calculation of the seismic hazard. At variance to previous models of the EMME region, we provide a homogeneous seismic source model representing a consistent basis for the next generation of seismic hazard models within the region.Published3465-34966T. Studi di pericolosità sismica e da maremotoJCR Journa

Planar seismic source characterization models for Gökova fault zone

Türkiye Yenilenmiş Diri Fay Haritası’nda (http://www.mta.gov.tr/v3.0/hizmetler/yenilenmis-diri-fay-haritalari) temel olarak karadaki faylar dikkate alınmış olduğundan, Gökova Fay Zonu’nun deniz içi bölümü bu haritada yer almamaktadır. 20 Temmuz 2017 Kos-Bodrum depremi (Mw:6.6) Gökova Fay Zonu’nun deniz içerisindeki bölümünü kırmış ve deprem sonrası yapılan çalışmalar fayın deniz içinde yer alan bölümü hakkında önemli veri sağlamıştır. Elde edilen veriler depreme kaynaklık eden 25 km uzunluğundaki güneye eğimli doğu-güneydoğu doğrultulu fay bölümünün 12 km sismik derinliğe sahip olduğunu işaret etmektedir. Öte yandan, Gökova Fay Zonu’nun Olasılıksal Sismik Tehlike Analizi’nde (OSTA) kullanılabilecek düzlemsel bir sismik kaynak olarak modellenmesi için gerekli olan yıllık kayma hızı, karakteristik deprem büyüklüğü, karakteristik depremin tekrarlanma aralığı, segmentasyon modeli gibi parametreler halen belirsizliğini korumaktadır. Bu çalışmanın temel amacı, fay bölümlerinin beraber ve/veya tek tek kırılma olasılıklarını mantık ağacı çerçevesinde ele alarak düzlemsel faylara dayalı bir sismik kaynak modeli oluşturmak ve bu modelleri kullanarak Gökova Körfezi için OSTA’ni gerçekleştirmektir. Önerilen bu modelde fay bölümleri, sismik kaynaklar ve kırılma senaryoları Amerika Jeoloji Araştırma Kurumu’nun (USGS) WGCEP-2003 terminolojisi kullanılarak tanımlanacak ve deprem kataloğundaki etkinlikler tanımlanan sismik kaynaklar ile eşleştirilerek senaryo ağırlıkları sismik enerjinin denkleştirilmesi yöntemi ile bulunacaktır. Çalışma sonucunda belirlenen 475 yıl dönüşümlü kuvvetli yer hareketi değerleri Türkiye Sismik Tehlike Haritası ile kaşılaştırılarak Kos-Bodrum depreminin yürürlülüğe girmesi planlanan bu harita üzerindeki olası etkisi irdelenecektir.In the Updated Active Fault Maps of Turkey (http://www.mta.gov.tr/v3.0/hizmetler/yenilenmis-diri-fay-haritalari) only the on-land faults are provided; therefore, the off-shore segment of the Gökova Fault Zone was not included in this map. The July 20, 2017 Kos-Bodrum Earthquake (Mw:6.6) had ruptured the off-shore segment of the Gökova Fault Zone, enlightening important features about the source parameters such as the fault geometry, orientation, and mechanism. Based on the recent field studies, the off-shore segment is defined as a 25 kmlong south-dipping normal fault with E-SE strike and 12 km seismogenic depth. However, the crucial parameters required to model the Gökova Fault Zone as a planar seismic source zone for probabilistic seismic hazard analysis (PSHA) such as the annual slip rate over the fault plane, characteristic magnitude, recurrence interval for the characteristic earthquake, and the segmentation model still involve significant uncertainties. The primary objective of this study is to develop a planar seismic source characterization model for Gökova Fault Zone that models these uncertainties and considers the single-segment and multi-segment ruptures in a systematic manner using a fully developed logic tree. Proposed model will define the fault segments, rupture sources, and rupture scenarios using the terminology given in Working Group of California Earthquake Probabilities (WGCEP-2003) report. Events in the seismological database will be attributed to the rupture system and the logic tree weights for the rupture scenarios will be determined by comparing the accumulated seismic moment due to the geological constraints (rupture dimensions and slip rate) with the seismic-moment release due to associated seismicity. The models will be utilized in the PSHA and the 475-years return period ground motions will be compared to the updated Turkish Seismic Hazard Map to evaluate the possible effects of Kos-Bodrum earthquake on the design ground motions provided in this map

The 10 June 2012 Fethiye Mw 6.0 aftershock sequence and its relation to the 24-25 April 1957 Ms 6.9-7.1 earthquakes in SW Anatolia, Turkey

The 10 June 2012 M-w, 6.0 aftershock sequence in southwestern Anatolia is examined. Centroid moment tensors for 23 earthquakes with moment magnitudes (M-w) between 3.7 and 6.0 are determined by applying a waveform inversion method. The mainshock is a shallow focus strike-slip with reverse component event at a depth of 30 km. The seismic moment (M-0) of the mainshock is estimated as 1.28 x 10(18) Nm and rupture duration of the Fethiye mainshock is 38 s. The focal mechanisms of the aftershocks are mainly strike-slip faulting with a reverse component. The geometry of the focal mechanisms reveals a strike-slip faulting regime with NE-SW trending direction of T-axis in the entire activated region. A stress tensor inversion of focal mechanism data is performed to obtain a more accurate picture of the Fethiye earthquake stress field. The stress tensor inversion results indicate a predominant strike-slip stress regime with a NW-SE oriented maximum horizontal compressive stress (S-H). According to variance of the stress tensor inversion, to first order, the Fethiye earthquake area is characterized by a homogeneous interplate stress field. The Coulomb stress change associated with the mainshock and the largest aftershock are also investigated to evaluate any significant enhancement of stresses along the Gulf of Fethiye and surrounding region. Positive lobes with stress more than 0.4 bars are obtained, indicating that these values are large enough to increase the Coulomb stress failure towards NNW-SSE and E-W directions. (C) 2014 Elsevier Ltd. All rights reserved