Probabilistic seismic-hazard estimation for Peninsular India

Peninsular India (10.0 degrees N-28.0 degrees N; 68.0 degrees E-90.0 degrees E) is one of the oldest and seismically most stable landmasses of the Indian plate. Recent seismic history, however, shows that more than five damaging earthquakes with magnitudes greater than M-w 6.0 have occurred in this region, highlighting the importance of seismichazard assessment for the region. This article estimates the probabilistic seismic hazard associated with peninsular India with a zoneless approach incorporating the observed seismic activity and known geological characteristics of the region. The seismicity parameters for hazard assessment have been estimated incorporating completeness criteria for various spans of the catalog data. The spatial and temporal variations of seismic activity have been modeled using different source models. Seismic source zones for the region have been defined on the basis of large-scale geological features, which are used for assigning the maximum possible earthquake potential. Due to the poorly known attenuation characteristics of the study region, three appropriate attenuation models have been used for the estimation of ground-motion parameters. Hazard maps for peninsular India have been developed using a convolution scheme based on weighting and incorporating various uncertainties involved while modeling different parameters. The comparison of the probabilistic seismic-hazard map developed herein with the hazard map specified in the Indian Standards shows that the design parameters in the Indian Standards may significantly underestimate the seismic hazard in some regions of peninsular India.