Frequency Dependent Attenuation Characteristics of Body Waves in Büyük Menderes Graben

Abstract

In this study, 66 earthquake data, along the faults of northern boundary of the Büyük Menderes Graben and their continuations in the Aegean Sea, were used to reveal the body wave attenuation characterization of the region. The attenuation functions of the P and S waves are calculated by the coda normalization technique. The results obtained in this study reveal attenuation relations, which are one of the basic parameters required to modelling large earthquakes in the region and to obtain more reliable results from necessary seismic risk studies. The power-law functions were obtained for the S and P seismic phases as Q_s=79.2±14.6f ^0.9±0.07 and Q_p=32.9±13.7f^1.05±0.16 respectively. Also the QS / QP ratio is calculated as ~ 1.75. for the frequencies greater than 1 Hz. According to the results, the low Qp and Qs values ​​and their ratios (QS / QP) indicate the abundance of scattering effect, which can be interpreted as a result of intense lateral heterogeneity in the upper crust.

Keywords

• Attenuation,Büyük Menderes Graben,Earthquake,P Wave,S Wave

Büyük Menderes Grabeninde Cisim Dalgalarının Frekans Bağımlı Soğrulma Karakterinin Belirlenmesi

Abstract

Bu çalışmada, Büyük Menderes grabeninin kuzey sınırı boyunca gelişen fay toplulukları ve bunların Ege Denizi’ne doğru uzantıları boyunca oluşmuş 66 deprem verisi kullanılarak bölgeye ait soğrulma karakteristikleri ortaya konmaktadır. Çalışmada, P ve S dalgalarının soğrulma fonksiyonları, koda normalizasyon tekniği ile hesaplanmıştır. Çalışma kapsamında elde edilen sonuçlar, bölgede veya yakın civarında gelecekte olması muhtemel büyük depremlerin daha doğru bir şekilde modellenebilmesi ve sismik risk çalışmalarının da daha güvenilir sonuçlar elde edilmesi için gerekli olan temel parametrelerden biri olan sönüm ilişkilerini ortaya koymaktadır.  Buna göre, S ve P sismik fazları için sırasıyla, Q_s=79.2±14.6f ^0.9±0.07 ve Q_p=32.9±13.7f^1.05±0.16 fonksiyonları elde edilmiştir. Ayrıca 1 Hz’ den büyük frekanslarda Q_S/Q_P oranı ortalama ~1.75 olarak hesaplanmıştır. Elde edilen sonuçlara göre düşük Qp ve Qs değerleri ve bunların oranları (Q_S/Q_P) saçılma etkisinin fazlalığını işaret etmekte ve bunun da çalışma alanındaki özellikle üst kabuktaki yoğun yanal heterojenitenin bir sonucu olduğu şeklinde yorumlanabilmektedir.

Keywords

• Soğrulma,Büyük Menderes Grabeni,Deprem,P Dalgası,S Dalgası

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