An Investigation of Local Site Effects on Strong Ground Motions in Abbas-Abad (Tehran Mosalla) Region

Local site effects play a very important role in characterizing seismic and design ground motions because they may strongly amplify (or deamplify) seismic motions before reaching the ground surface.
The purpose of this paper is to evaluate local ground response in ABASBAD region (around the TEHRAN MOSALLA). To perform dynamic analysis, soil layers dynamic characteristics is determined from seismic down-hole tests performed at 6 borehole stations. Bedrock Seismicity characteristics is evaluated and 15 accelerograms from various earthquakes around the world is selected. Considering the local topography and soil conditions, one dimensional equivalent linear analysis is performed and results is presented in form of microzonation maps of maximum ground acceleration and velocity, maximum amplification and site specific design spectra. The results indicate that presence of stiff shallow granular soil layers has no considerable affect on bedrock seismic motions and using Iranian earthquake code (2800) normalized design spectra for this site, is conservative at long periods.