Evaluation of Site Effects by Soil and Sediments in Karaj, Iran

Abstract

As an important step in effectively reducing seismic risk and the vulnerability of the city of Karaj to earthquakes, a site effect microzonation Study was conducted. Seismic hazard analysis for a return period of 475 years was carried out. Data from 66 borings was collected and analyzed, geophysical surveys were conducted and seismology and geoelectric measurements taken in more than 17 stations throughout the city. The study area was divided into a grid of 500∗500m2 elements and the sub-surface ground conditions were classified into 9 representative geotechnical profiles. Electric resistivity was measured in close to 20 geotechnical boreholes and surface and sub-surface sediments were collected and analyzed. Site response analyses were carried out on each representative profile using 30 different base rock input motions. Distribution maps of site periods and peak ground acceleration and old and new texture buildings throughout the city were developed, providing a useful basis for land-use planning in the city.