AN ALTERNATIVE METHOD FOR THE ESTIMATION OF b-VALUE IN THE GUTENBERG-RICHTER RELATION WITH AN APPLICATION IN SOUTHWEST OF TURKEY

Öz

In this study, the spatial distribution of seismicity and seismic hazard is undertaken for the Southwest of Turkey. For this purpose, the earthquakes of magnitude of M≥4 which were occurred between 1964 - 2002 were used in Southwest of Turkey. For the estimation of seismicity parameters and its mapping, Southwest of Turkey is divided into 169 rectangular subregions. The b value from the Gutenberg-Richter frequency-magnitude distributions is calculated by least squares method with a new alternative method and compared with the results directly calculated by least squares method. The a value in the Gutenberg-Richter frequency-magnitude distributions is taken a constant value in the new alternative method. The b value shows different distributions along the Southwest of Turkey for both techniques. From the new technique, low b-values are dominant in the western part of the studying region, while higher b-values are present in the eastern part. Finally, the return period and occurrence probability risk of M≥6 earthquakes in 75 years were calculated using Poisson model for both techniques. Maps of the occurrence probability risk and return period showed a better consistency with the b parameters seismicity maps calculated from new method. Moreover, the return period and occurrence probability risk maps calculated from both techniques showed a better consistency,with each other. The occurrence probability risk and return period of M≥6 earthquake were calculated as %90-95 and 15-30 years, respectively, from the Poisson model in the western part of the studying region.

Anahtar Kelimeler

• Gutenberg-Richter b value, Seismic risk, Seismicity, Southwest of Turkey

GUTENBERG- RICHTER BAGINTISINDAKİ b DEĞERİNİN TESPİTİ İÇİN ALTERNATİF BİR METOT VE GÜNEYBATI TÜRKİYE'DE BİR UYGULAMASI

Öz

Çalışmada Güneybatı Türkiye’nin sismik riski ve sismisitesinin uzaysal dağılımı ele alınmıştır. Bu amaç için 1964–2002 yılları arasında bölgede meydana gelen M≥4 olan 722 adet deprem verisi kullanılmıştır. Sismisite parametrelerinin belirlenebilmesi ve haritalanması için çalışılan alan 169 alt bölgeye ayrılmıştır. Her bir alt bölge için, Gutenberg-Richter magnitüd-frekans bağıntısındaki b değeri en küçük kareler tekniği ve yeni bir alternatif metotla hesaplanarak doğrudan en küçük karelerden elde edilen sonuçlar ile karşılaştırılmıştır. Yeni alternatif metotta Gutenberg-Richter bağıntısındaki a parametresi sabit alınmıştır. Güneybatı Türkiye boyunca her iki teknik içinde b değeri farklı değişim göstermiştir. Yeni alternatif metot ile Güneybatı Türkiye’nin Doğusu yüksek b değeri gösterirken, Batı kanadında düşük b değerleri baskın olarak bulunmuştur. Son olarak, her iki teknikle de Poisson modeli kullanılarak çalışma alanı içerisinde M≥6 depremin 75 yıllık bir süreçte oluşma riski ve dönüş periyotları hesaplanarak haritalanmıştır. Her iki teknikle oluşturulan risk ve dönüş periyodu haritaları alternatif metotla oluşturulan b parametresi sismisite haritalarıyla oldukça uyumlu olarak bulunmuştur. Ayrıca, her iki teknikle de elde edilen risk ve dönüş periyotları bir biri ile tamamen uyumludur. Çalışma alanının Batı kanadında M≥6 bir depremin oluşma riski %90–95 ve dönüş periyodu da 15– 30 yıl olarak elde edilmişti

Anahtar Kelimeler

• Gutenberg-Richter b değeri, Sismik risk, Sismisite, Güneybatı Türkiye

Kaynakça

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