Focal Mechanisms of the January 22, 2020 Akhisar-Manisa Earthquake (Mw 5.5) and Its Aftershocks: Seismotectonic Implications

Abstract

Focal mechanism solutions of the January 22, 2020 Akhisar-Manisa (M_w 5.5) earthquake and its aftershocks were obtained by using moment tensor inversion in order to make a seismotectonic interpretation for the study area. Total of 35 focal mechanism including the main shock have been obtained by using ISOLA algorithm. The results indicated that the majority of the focal mechanism solutions are normal faulting and normal faulting with strike slip component and some are strike slip faulting with normal faulting component. The results are compatible with the tectonics of the region. Focal depths of the analysed earthquakes are ranging between 4 and 15 km. The stress inversion of the studied earthquakes show that the present-day stress field is characterized by pure extensional regime (R’=0.75) and the study area is opening NE-SW. The horizontal direction of extension at N21^o E. Axis orientations are found as 74^o /111^o, 16^o/291^o and 0^o/201^o (dip/azimuth direction) for σ_1, σ_2, and σ_3, respectively. According to these stress distributions, the fault planes on which earthquakes occur indicate extensional tectonic crustal deformation.

Keywords

• Earthquake Source Mechanism,moment tensor analysis,NW trending normal fault,extensional tectonics

22.01.2020 Akhisar-Manisa Depremi (Mw 5.5) ve Artçılarının Sismotektonik Analizi

Abstract

Bu çalışmada, 22 Ocak 2020 Akhisar-Manisa (M_w 5.5) depremi ve artçılarının odak mekanizması çözümleri dalga şekli ters çözümü ile elde edilmiş ve buna göre sismotektonik yorum yapılmıştır. Bu amaçla, ana şok ve 35 artçı depremin odak mekanizması çözümleri ISOLA algoritması ile elde edilmiştir. Depremlerin odak mekanizması çözümlerinin çoğunluğu, bölgenin genişleme tektoniği ile uyumlu olup, normal faylanma ve az miktarda doğrultu atım bileşeni olan normal faylanma veya normal faylanma bileşeni olan doğrultu atımlı faylanma özelliğine sahiptir. Analizi yapılan depremlerin odak derinlikleri 4-15 km arasında değişmektedir. Gerilme tensörü ters çözümüne göre; bölge açılma rejiminin (R’=0.75) etkisi altındadır ve KD-BG yönünde açılmaktadır. Açılma hızı 1.3 mm/yıl olarak hesaplanmıştır. Bölgede minimum basınç ekseni (σ3), K21^oD olarak yönlenmiştir. Asal gerilme eksenlerinin bölgedeki konumları sırasıyla σ_1, σ_2, ve σ_3 olmak üzere 74^o /111^o, 16^o/291^o ve 0^o/201^o (eğim/azimut) olarak hesaplanmıştır. Bu stres dağılımlarına göre depremlerin üzerlerinde meydana geldiği fay düzlemleri, gerilmeli tektonik kabuk deformasyonunu işaret etmektedir.

Keywords

• Deprem kaynak mekanizması,moment tensör analizi,KB doğrultulu normal fay,gerilme tektoniği

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