Relevance of hot underlying asthenosphere to the occurrence of Latur earthquake and Indian peninsular shield seismicity

The cause of the highly destructive Latur earthquake of September 30, 1993, which occurred below the flood basaltic region of the Indian peninsular sh ield killing more than 10,000 people, is still not well understood despite several geoscientific investigations carried out after the main event. In t he present work, we have examined in detail multiparametric geophysical dat a to understand its origin in particular and the seismicity of the Indian s hield in general. Our study suggests that the Indian peninsular region is c haracterised by large variation in asthenospheric depths from 31 km to 186 km, depending on tectonic segments. The unusual seismic activity thus appea rs to stem from hot and upwarped underlying asthenosphere, which causes con tinuous build-up of localised stresses due to differential isothermal rise, and large lateral temperature differences on a regional scale beneath the highly fragmented Indian shield. The shield appears to be undergoing large scale rejuvenation and has become much more unstable than other global shie lds. (C) 1999 Elsevier Science Ltd. All rights reserved.