Spatial Analysis of A-Value and B-Value Variability in Alborz

Abstract

This study was conducted to evaluate seismic hazard parameters (a-value and b-value of the Gutenberg–Richter) and Magnitude of completeness (Mc) in Alborz area. The b-value explains the relative density of small and large earthquakes which is a key issue in seismic hazard studies and a-value is concerned with regional seismicity level, so studying these parameters can be of great help particularly in mega cities with high rate of population. This study area is situated in Azerbaijan-Alborz seismotectonic province. For this assessment first, earthquake catalog and data have been collected from ISC, USGC and BHRC from 1990 to 2010. Magnitude of completeness has been estimated 3.5 so for the magnitude equal or bigger than 3.5 the catalog is complete. After processing data, eliminate aftershocks and fore shocks and homogenize the catalog. Spatial distributions of the estimated a-value and b-value in Iran have been obtained by dividing the area in small grids (0.5˚x0.5˚). The b-value in the study area is from 0.55 to 1 and a-value ranges from 3.4 to 4.1.