Delineation of probable seismic sources in India and neighbourhood by a comprehensive analysis of seismotectonic characteristics of the region

Identification and delineation of seismogenic sources is one of the most important steps in the seismic hazard analysis. This paper presents a comprehensive description of the various tectonic features and the association of seismicity with them to define the probable seismic sources in India and adjacent areas. The plate boundary areas along the Himalayan and the Indo-Burmese arcs, along with the intervening area of northeast India, are characterized by very high level of seismicity. To consider the spatial variation in the seismicity, these areas are divided into several possible seismic sources. In view of the sporadic nature of seismicity in the intraplate area of the peninsular India, it is represented by 21 isolated sources. From a knowledge of the subsurface peninsular features extending up to the Himalaya and the seismicity associated with them, some seismic sources are also delineated transverse to the Himalayan trend in the Indo-Gangetic plains. In all, 81 broad seismic sources are defined by a detailed and critical analysis of the correlation of more than 12,000 past earthquakes with magnitude 4.0 or above with the major tectonic features in the Indian region. Due to the use of an up-to-date database on the past seismicity and a very comprehensive analysis of the seismotectonics of the region, the present study is considered to provide a very realistic basis for evaluation of seismic hazard in India.