Performance Analysis of Existing Vs30 Prediction Models for Turkey and New Approaches to Improve / Mevcut Vs30 Tahmin Modellerinin Türkiye için Performans Analizi ve İyileştirilmesine Yönelik Yeni Yaklaşımlar

Okay H. B., Özacar A. A.

74st Geological Congress of Turkey, Ankara, Türkiye, 11 Nisan 2022, ss.230

  • Yayın Türü: Bildiri / Özet Bildiri
  • Basıldığı Şehir: Ankara
  • Basıldığı Ülke: Türkiye
  • Sayfa Sayıları: ss.230
  • Orta Doğu Teknik Üniversitesi Adresli: Evet

Özet

Various parameters are used for geotechnical characterization and considering seismic site conditions. Among them, the most widely used one is the average shear wave velocity (Vs30) of the first 30 meters of the Earth's surface. Within the scope of the study, Vs30 measurements of accelerometer stations which are operated by the Disaster and Emergency Management Presidency (AFAD) throughout Turkey, were mapped, and the slope and elevation values of these points were calculated using high resolution digital elevation models. In addition, the geological units and the morphological terrain classes in which the stations are located were determined, and their correlations with the measured Vs30 values were examined. As expected, the Vs30 values were found sensitive to slope, morphology, and geology, while the sensitivity to elevation was weak. Two different Vs30 prediction models were examined for performance analysis. The predictions of the global Vs30 model of the United States Geological Survey (USGS), which is based on the topographic slope for different soil classes, differ from the measurements in Turkey, especially in low-slope regions. On the other hand, the Vs30 prediction model based on the available borehole and geophysical data throughout Italy which includes different factors such as lithology, slope, morphological land classes, and elevation, resulted in generally higher Vs30 values than the measured ones across Turkey. Performance analysis results showed that current Vs30 prediction models across Turkey are especially less consistent in younger units characterized by low Vs30 values. This implies that a more detailed characterization of young lithologic units is needed for Vs30 prediction. In this study, classification of young units on the basis of water saturation level was established using spatial factors, and new Vs30 prediction models were developed. This approach better reflects the divergent Vs30 values observed in younger units.