Low cost seismic microzonation using microtremor data: an example from Delhi, India

Abstract

Measurement and analysis of microtremor data has proved to be an efficient and low cost method of seismic hazard microzonation. The seismic hazard microzonation for ground shaking site effects have been determined from 75 microtremor measurements in and around Delhi, India. These data were used for the estimation of the fundamental resonance frequency and amplification of ground vibration. It is observed that these two parameters vary considerably from one area to another. The resonance frequency of a site becomes lower when the basement depth increases and vice versa. The resonance frequency is lower in areas having younger alluvial deposits. The amplification of ground vibration has been determined in terms of the lower bound estimate of the level of amplification. It is higher in the Trans-Yamuna area towards east (i.e. east of Yamuna river) compared to the rest of Delhi. Earthquake data available from two sites, and a soil layer structure available from one site, were used for correlation and shows a good match between resonance frequency estimated by microtremor data and that estimated from earthquake and soil structure data.