Generation and Comparison of Different Forms of Attenuation Relationships for the Western Anatolia, Turkey

The western Anatolia is one of the good examples of fast intra-continental extensional tectonics with active extensional stress rate about 3-4 cm/year. Increasing lithospheric thinning causes increasing geothermal activities in the region and active tectonics has generated seismic activity with destructive earthquakes. Moderate sized earthquakes in the region are actually the dominant source of seismic hazard, because of their larger amplitudes at longer periods in deep basin structures of western Anatolia graben system. Due to extensive exposure and vulnerability to the effects of earthquakes, seismic hazard assessment is very important issue in the region. In this study we described predictive peak ground acceleration and 5%-damped spectral acceleration attenuation relationships for western Anatolia by regressing strong-motion data (e.g. Joyner and Boore 1981; Ambraseys et al. 1996; Boore et al. 1997). In order to do so, we use strong motion records from the stations which are located in the region and operated by the General Directorate of Disaster Affairs’ Earthquake Research Department (ERD) and additionally the data from WASRE network (Akyol et al., 2006). Comparison of obtained attenuation relationships with the ones generated for tectonically different regions have shown that ground motion attenuation relationships in a specific region can not be simply modified for use in engineering analysis for the other regions. On the other hand, comparison of obtained attenuation relationships with the ones generated for tectonically similar regions have shown that our model estimation is lower. This result is consistent with reported low velocities and high attenuation values of crustal structures in the region.