Evaluation of seismicity and seismic hazard parameters in Turkey and surrounding area using a new approach to the Gutenberg-Richter relation

In this study, the spatial distributions of seismicity and seismic hazard were assessed for Turkey and its surrounding area. For this purpose, earthquakes that occurred between 1964 and 2004 with magnitudes of M≥4 were used in the region (30-42°N and 20-45°E). For the estimation of seismicity parameters and its mapping, Turkey and surrounding area are divided into 1,275 circular subregions. The b-value from the Gutenberg-Richter frequency-magnitude distributions is calculated by the classic way and the new alternative method both using the least-squares approach. The a-value in the Gutenberg-Richter frequency-magnitude distributions is taken as a constant value in the new alternative method. The b-values calculated by the new method were mapped. These results obtained from both methods are compared. The b-value shows different distributions along Turkey for both techniques. The b-values map prepared with new technique presents a better consistency with regional tectonics, earthquake activities, and epicenter distributions. Finally, the return period and occurrence hazard probability of M≥6.5 earthquakes in 75 years were calculated by using the Poisson model for both techniques. The return period and occurrence hazard probability maps determined from both techniques showed a better consistency with each other. Moreover, maps of the occurrence hazard probability and return period showed better consistency with the b-parameter seismicity maps calculated from the new method. The occurrence hazard probability and return period of M≥6.5 earthquakes were calculated as 90-99% and 5-10 years, respectively, from the Poisson model in the western part of the studying region.[PUBLICATION ABSTRACT]