Seismicity assessment for the different regions in and around Turkey based on instrumental data: Gumbel first asymptotic distribution and Gutenberg-Richter cumulative frequency law

Abstract

The evaluation of the seismicity in 24 seismic re gions, in which Turkey and adjacent areas divided, is car ried out. For this purpose two methods are adopted. The first is the “whole process” which follows the Gutenberg and Richter distribution frequency-magnitude law, while the sec ond one is the “part process” which is well known as the the ory of extreme values. This theory was developed by Gum bel in order to solve many geophysical problems. The first asymptotic distribution of extremes was used in the present study. The advantage of the method is that it does not re quired analysis of the whole data set. It uses, instead, the sequence of earthquakes with the largest magnitudes in a set of predetermined equal-time intervals. The parameters a and b were estimated from both methods. For the goodness of fit, to the Gutenberg-Richter frequency-magnitude law, the max imum likelihood approach is applied. The b-values calcu lated from Gutenberg and Richter frequency-magnitude law, reveal a better fit to the tectonic environment of the 24 seis mic regions of Turkey and its surroundings examining in this study. On the other hand b-values evaluated from Gumbel’s first distribution, do not adjust to the particular tectonics of the 24 seismic regions. The modal value a1/b adopted from Gutenberg-Richter for the 24 seismic regions were calcu lated, as well. An effort made to correlate the tectonics of the area with the spatial distribution of the various computed seismic pa rameter, while maps were produced for this purpose. These maps provide a detail image of seismicity and local tecton ics for the whole investigated area. The results showed that the Aegean arc and the North Anatolian fault zone ranked among to the first positions between the 24 seismic regions researched.