Determination of shear wave velocity profile of sedimentary deposits in Bam city (southeast of Iran) using microtremor measurements

摘要

Site effect has been known as the major cause of large ground amplifications during several recent catastrophic earthquakes. Consequently, the evaluation of site effect is an important factor that must be considered in mitigation of earthquake hazards. Shear wave velocity is a key parameter that controls dynamic response of a site. Hence its profile must be identified down to the seismic bedrock. Generally geotechnical or even geophysical methods are expensive and time consuming for this purpose. As an economical and practical substitute, microtremor measurements can be used. In order to investigate the reliability of shear wave velocity (V_s) profiling by using microtremors, a series of microtremor measurements have been conducted in Bam city (southeast of Iran) which experienced the damaging earthquake of December 2003. Microtremor measurements included both one-point and array observations. However, only the array measurement data are considered in this study. Based on the dispersion characteristics of Rayleigh waves, V_s profiles were determined at array measurement sites using inverse analysis. Ultimately, reliability of the inverted soil profiles was investigated, comparing results of microtremor measurements and seismic refraction and down-hole methods.