Representative seismic hazard map of Coimbatore, India

The seismic hazard value of any region depends upon three important components such as probable earthquake location, maximum earthquake magnitude and the attenuation equation. This paper presents a representative way of estimating these three important components considering region specific seismotectonic features. Rupture Based Seismic Hazard Analysis (RBSHA) given by Anbazhagan et al. (2011) is used to determine the probable future earthquake locations. This approach is verified on the earthquake data of Bhuj region. The probable earthquake location for this region is identified considering earthquake data till the year 2000. These identified locations match well with the reported locations after 2000. The further Coimbatore City is selected as the study area to develop a representative seismic hazard map using RBSHA approach and to compare with deterministic seismic hazard analysis. Probable future earthquake zones for Coimbatore are located considering the rupture phenomenon as per energy release theory discussed by Anbazhagan et al. (2011). Rupture character of the region has been established by estimating the subsurface rupture length of each source and normalized with respect to the length of the source. Average rupture length of the source with respect to its total length is found to be similar for most of the sources in the region, which is called as the rupture character of the region. Maximum magnitudes of probable zones are estimated considering seismic sources close by and regional rupture character established. Representative GMPEs for the study area have been selected by carrying out efficacy test through an average log likelihood value (LLH) as ranking estimator and considering the Isoseismal map. New seismic hazard map of Coimbatore has been developed using the above regional representative parameters of probable earthquake locations, maximum earthquake magnitude and best suitable GMPEs. The new hazard map gives acceleration values at bedrock for maximum possible earthquakes. These results are compared with deterministic seismic hazard map and recently published probabilistic seismic hazard values.