Deprem Kayıtlarından Elde Edilen Yatay/Düşey Spektral Oranların Ters Çözümüyle Kayma Dalga Hız Yapısının Belirlenmesi: Van Gölü Doğusu Örneği

Van Gölü doğusu farklı özellikteki aktif fayların varlığı sebebiyle deprem üretme potansiyeli yüksek olan bir bölgedir. Depremlere bağlı oluşan hasarların değerlendirilmesinde yeraltının fiziksel özelliklerinin ve deprem sırasındaki davranışının iyi bilinmesi gerekmektedir. Kayma dalgası hız değişimi ve anakaya derinliğinin belirlenmesi bu açıdan son derece önemlidir. Bu çalışmada 2011-2021 yılları arasında Van Gölü doğusunda meydana gelen ve farklı tipteki faylarda oluşmuş dokuz deprem verisinden yararlanılmıştır. 6 istasyonda kaydedilen depremler yatay-düşey spektral oran yöntemi ve Monte-Carlo ters çözüm algoritması ile analiz edilerek, kayma dalgası hız yapısı ve anakaya derinlikleri belirlenmiştir. İstasyonlar altında alüvyon birimlerinin kalınlığına bağlı olarak nispeten düşük frekans değerleri elde edilmişken, farklı kaya birimlerin varlığı baskın frekans değerlerini yükseltmiştir. Spektral oran eğrilerindeki farklı frekanslardaki pikler, jeolojik yapının özelliklerine bağlı olarak değişkenlik göstermiştir. İstasyon altı anakaya derinliği 10-350 m arasındadır. Artan anakaya derinlik seviyeleri yıkıcı depremlerin hasar oranını arttıran bir faktördür.

Anahtar Kelimeler:

Anakaya derinliği, Deprem, EHVSR, Kayma dalga hızı

Determination of Shear Wave Velocity Structure by Using Inversion of Horizontal/Vertical Spectral Ratios Obtained from Earthquake Records: Example from the East of Lake Van

The eastern part of the Lake Van region has a high potential to produce destructive earthquakes due to the presence of active faults with different mechanisms. To evaluate the damages of earthquakes, it is well known the physical properties of the underground and its behavior during the earthquake. Determination of the depth-dependent shear wave velocity variation and bedrock depth is extremely important in this respect. In this study, nine earthquakes data that occurred on different types of fault between 2011-2021 in the east of the Lake Van region are used. 6 station earthquake data is analyzed using the H/V spectral ratio and the Monte-Carlo inversion, and the shear wave velocity structure and bedrock depths are calculated. The low-frequency values are relatively defined depending on the thickness of the alluvial units under the stations, whilst the presence of different rock units increases the frequency values. The peaks at different frequencies in the spectral ratio curves show variability depending on the characteristics of the geological structure. The bedrock depth under the station is between 10-350 m. Increasing bedrock depth levels are a factor that increases the damage rate of destructive earthquakes.

Keywords:

Bedrock depth, Earthquake, EHVSR, Shear wave velocity,

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