Short Period Spectral Acceleration Zonation of Tehran a Comparison between Slip and Activity Rates Data’s

Abstract

This study presents seismic hazard analysis and provides spectral iso acceleration maps based on slip rate (SR) and also activity rate (AR) of the faults. Nowadays modern seismic design of structures is complicated so special attention to the nature of the seismicity in active seismic zones like Tehran is required. Many studies, based on seismic hazard analysis have been done in Tehran. However, none of these studies provided comparison between SR, AR and spectral seismic zonation. In order to reduce the loss of life and property in metropolitan Tehran such studies are undeniable. The process of this study is identification of seismic sources, estimation of seismic parameters and interpretation the results of paleoseismology. Seismic hazard assessment for grid points has been done based on seismic sources and the determination of shear wave velocity. Based on these studies, the shear wave velocity for the upper 30 m has been prepared as a basic parameter for seismic hazard analysis. In addition, iso acceleration spectral maps were prepared based on the SR and AR, for 475 years return period. Referring to paleoseismology studies, it is apparent that some faults in South and South East of Tehran should be considered as an ancient coast line; therefore, they were excluded from the seismic studies. As a result, acceleration in South East Tehran has dramatically declined. In a general comparison, it can be stated that the acceleration based on data from the SR is higher than the AR for the period of 0.4 seconds. The results are equal, in period of 0.4 s and after that the acceleration based on AR is higher than SR.