Comparison of the attenuation properties for two different areas in eastern Anatolia, Turkey

摘要

In this study, the attenuation properties of the crust and the quality factor of S wave in eastern Anatolia (Turkey) were determined by local earthquakes for two different areas, Oltu and Erzurum. Seismic wave attenuation can be changed with high pressure or structural effects. Therefore, we argued that the estimation of attenuation coefficient in seismic active zones in Eastern Anatolia is a very useful tool to determine seismic activities. It uses regional waveform data set from two stations, OLT and ERZ, for 95 events that occurred in these regions between 2001 and 2005. The attenuation has been determined using the Chobra-Alexeev model based on the epicenter distance-amplitude relations. This model allows for investigation of the effects of variations in attenuation properties for different areas. We introduced a new magnitude formula for these areas using the amplitude normalization methods for reference values M_L=4, so as to correct effects of the magnitudes. We also determined velocity of seismic waves. The average attenuation coefficient (a), average quality factor (Qs) and P and S waves velocities were obtained with normalized amplitude values for Erzurum (ERZ) and Oltu (OLT) as 0.0135 km-1, 37, 6.20 km/s and 3.38 km/s and 0.0151, 34, 6.13 and 3.48.