Site Effect Microzonation and Seismic Hazard Analysis of Kermanshah Region in Iran

As an important step in effectively reducing seismic risk and the vulnerability of the city of Kermanshah to earthquakes, a site effect microzonation study was conducted. Seismic hazard analysis for a return period of 475 years was carried out. Data from 113 borings was collected and analyzed, geophysical surveys were conducted and microtremor measurements taken in more than 60 stations throughout the city. The study area was divided into a grid of 1x1 km2 elements and the sub-surface ground conditions were classified into 14 representative geotechnical profiles. Site response analyses were carried out on each representative profile using 14 different base rock input motions. Distribution maps of amplified acceleration for a return period of 475 years and peak ground acceleration throughout the city were developed, providing a useful basis for land-use planning in the city. It was found that three active or potentially active quaternary faults with distinct evidence of surface displacements within Holocene or Pleistocene times lay within the city. This implies the necessity of considering surface fault-rupture hazard as well as other near field effects in planning future construction in these neighbourhoods. The presence of a significant amplification peak in the frequency interval of 0.8 to 1.5 Hz (period interval of 0.6 to 1.1s) throughout the city is observed by the microtremor H/V display ratios which implies that prospective high-rise buildings (more than 14 stories) may be endangered.