Investigation of the relation between Vs30 and site characteristics of Iran based on horizontal-to-vertical spectral ratios

It is well known that the ground-motion amplitude of an earthquake could be extensively influenced by site effect. This study aims at providing a simple and new site amplification model for Iran based on the site fundamental frequency (f(peak)) obtained from horizontal-to-vertical spectral ratio (HVSR). For this purpose, as a more reliable predictor of site amplification, HVSR have been calculated from pseudo-spectral acceleration of Iranian ground motions database consisted of 560 records from 30 events with moment magnitude ranging from 3.7 to 7.7 at epicentral distance of 1.7-297 km. Proposed HVSR model for Iran has been compared with the other regional models developed for California, Japan, Taiwan, Italy and China. In addition, the correlation of measured time-averaged shear wave velocity in the upper 30 m (V-s30) in different seismograph stations with site fundamental frequency is evaluated and a new predictive relation for V-s30 has been proposed for the study area.