Investigation of Arias Intensity for Ankara and Surroundings

The amplitude, peak ground acceleration and spectral ordinates are the main components of strong ground motion investigation for design within seismic regions. In this study, variation of Arias intensity as used for liquefaction and seismic slope stability was extracted from the acceleration records for the city of Ankara, whicih is located at the conjunction of several active faults. The study included the earthquake records with magnitudes greater than 4.0 with particular emphasis on December 27th 2007 Bala earthquake, since the epicenter of such earthquake is closest to Ankara. The mainshock of Bala earthquake was felt strongly around western Ankara, especially nearby new residential areas. Earthquakes of Afyon-Dinar (1995), Çay (2002), Düzce (November 12 1999), Çankýrý-Orta (2002) and two earthquakes recorded at 2014 and 2015 within Eskiþehir city were also included. Arias intensity includes the total duration and frequency content of earthquake when compared to peak ground acceleration. The variation of Arias intensity was calculated in order to determine the main energy release durations. Attenuation of Arias intensity was obtained based on the distance between the study area and recorder stations. The design Arias intensity value for central Ankara was attained including the stress drop for different fault types for rock and soil conditions. Peak Arias Intensities for 50 km and 100 km around Ankara are 0.2 m/s and 0.1 m/s. More detailed studies should be implemented to employ such values for liquefaction and seismic slope stability.

Ankara Çevresi Ýçin Arias Þiddetinin Ýncelenmesi

Kuvvetli yer hareketi incelemelerinde genlik, en büyük yatay yer ivmesi ile spektral parametreler sismik açýdan tehlikeli alanlarda yapý dizaynýnda kullanýlan temel bileþenlerdir. Bu çalýþmada, bir çok aktif fayýn kesiþme noktasýnda yer alan Ankara çevresindeki ivme kayýtlarý derlenerek, sývýlaþma ve sismik þev duraylýlýðýnda da kullanýlan Arias þiddetinin deðiþimi incelenmiþtir. Büyüklüðü 4.0’den büyük olan deprem kayýtlarý incelenerek, özellikle odak noktasý Ankara þehir merkezine en yakýn olan 27 Aralýk 2007 Bala depremi kayýtlarý dikkate alýnmýþtýr. Bu depremin ana þoku Ankara ilinin batýsýnda, yeni yerleþimlerin bulunduðu yerlerde yoðun þekilde hissedilmiþtir. Ayrýca; Afyon-Dinar (1995) ile Çay (2002) depremleri, Düzce (12 Kasým 1999) depremi, Çankýrý-Orta (2002) depremi ve Eskiþehir’ de 2014 ve 2015 yýllarýnda kaydedilmiþ olan iki adet deprem incelenerek çalýþmanýn kapsamýna alýnmýþtýr. Kuvvetli yer hareketi incelemelerinde, özellikle depremin toplam süresi ve frekans içeriðinin dikkate alýndýðý Arias þiddetinin kayýtçýlardaki zamana baðlý deðiþimi hesaplanarak enerji boþalým süreleri belirlenmiþtir. Kaya ve zemin için geliþtirilen eþitliklerin farklý fay türlerine göre gerilme azaltma deðerleri de deðerlendirilerek, Ankara ve yakýn çevresi için dizayn Arias þiddeti belirlenmiþtir. Ankara’ya 50 km ve 100 km mesafede oluþacak bir depremde en yüksek Arias þiddeti 0.2 m/s ve 0.1 m/s elde edilmiþtir. Elde edilen deðerlerin sývýlaþma ve sismik þev duraylýlýðý çalýþmalarýnda kullanýlmasý için daha detaylý çalýþmalar yapýlmalýdýr.