İbrahim Hakan DEMİRSIKAN, Şakir ŞAHİN, Erdinç ÖKSÜM

Orta Anadolu’da kabuğa ait sismik P ve S dalga hızı yapısının belirlenmesi

Bu çalışmada, Orta Anadolu’da yerel depremlerin varış zamanlarından hareketle Poisson oranı Tomografisi metodu kullanılarak üç boyutlu (3-B) hız yapısını belirlenmiştir. Bu çerçevede, toplam 27.141 adet depreme ait 109.740 adet P dalgası ve 102.934 adet S dalgası varış zamanı verisi kullanılmıştır. Depremler Boğaziçi Üniversitesi, Kandilli Rasathanesi ve Deprem Araştırma Enstitüsü’ne (KRDAE) bağlı Ulusal Pasif Hareket Sismik Ağı’na bağlı istasyonlar tarafından kaydedilmiştir. İnceleme alanında bulunan deprem istasyonları ve deprem merkez üssü dağılımı, elde edilen Vp ve Vs hız dağılımının 40 km’ye kadar güvenilir sonuç verdiğini göstermektedir. Dama tahtası (Checkerboard) çözünürlük testi ve ışın yolu dağılımları bu durumu doğrulamaktadır. Tomografik sonuçlar, Orta Anadolu’da kabuk ve üst mantoda yanal heterojenliklerin varlığına işaret etmektedir. Depremlerin bölgedeki karmaşık tektonik ve jeolojik yapıdan dolayı genel olarak sismik hızın düştüğü alanlarda oluştuğu dikkati çekmektedir. Düşük veya yüksek hız değerlerine sahip olan tüm bölgelerin gerilme enerjisi birikimi için potansiyel alanlar olduğunu görülmektedir. Elde edilen P ve S dalga hızı modelleri, Orta Anadolu'daki mevcut sismotektonik yapıyı net bir şekilde ortaya koymaktadır.

Anahtar Kelimeler:

P ve S dalga hızları, Sismik tomografi, Orta Anadolu, Sismik hız

Determination of seismic P and S wave velocity structure of crust in Central Anatolia

In this study, the three-dimensional (3-D) velocity structure was determined by Poisson ratio Tomography method based on the arrival time of local earthquakes in Central Anatolia. For this purpose, 109.740 P-wave and 102.934 S-wave arrival time data from 27.141 earthquakes were used. Earthquakes were recorded by stations related to the National Passive Motion Seismic Network of Bogazici University, Kandilli Observatory and Earthquake Research Institute (KOERI). Distribution of the stations and earthquake epicenters shows that the Vp and Vs velocity model yield reliable results up to 40 km depth. Checkerboard resolution test and ray path distributions confirm this situation. Tomographic results indicate the presence of lateral heterogeneities in the crust and upper mantle in Central Anatolia. It is remarkable that the earthquakes occur in areas where the seismic velocity is low due to the complex tectonic and geological structure in the region. The results of the study show that all regions with low or high seismic velocities are potential areas for the accumulation of stress energy. Resulting P- and S-wave velocity models clearly show the existing seismotectonic structure in Central Anatolia.

Keywords:

P and S wave velocity, Seismic tomography, Center Anatolia, Seismic velocity,

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