Assessment of seismic vulnerability index of RAJUK area in Bangladesh using microtremor observations

Abstract

Microtremor Horizontal to Vertical spectral ratio technique, also known as the Nakamura’s method is growing in status for site response analysis. 500 locations in RAJUK area (1530 km2) have been selected for microtremor observations. Microtremor data have been compiled and studied to estimate the predominant resonance frequency and H/V peak amplitude following the SESAME (2004) guideline. Finally, seismic vulnerability index of site soil using Nakamura’s technique has been determined from predominant resonance frequency and H/V peak amplitude parameter. The calculated seismic vulnerability index for the studied 500 locations varies between 0.16 and 7.28. The low seismic vulnerability index (Kg) value means that the areas are relatively stiff and underlain by substantial deposit of sediments. The relatively higher Kg values are spread in the soft alluvial deposit areas. The areas with high Kg values are considered as fragile zones that may initiate significant damage to infrastructure situated in those areas during an earthquake.