Characterization of Regional Seismic Source Zones in and around India

Abstract

Online material : Earthquake catalog; coordinates of source zones; list of events in each zone; frequency magnitude distribution plots. Identification and characterization of seismic sources are essential input for seismic hazard analysis. A complete and consistent catalog of earthquakes in a region can offer good data for studying the distribution of earthquakes with respect to space, time, and magnitude. Earthquakes are known to have occurred in the region of the Indian subcontinent from historic times. Most of the activities, including many great earthquakes, have occurred in the northern subcontinent and in the Andaman and Nicobar regions. In the southern peninsula, damaging earthquakes have occurred, but their frequency was less and magnitudes were lower than the plate boundary earthquakes. The tectonic framework of the Indian subcontinent—an area of about 3.2 million square kilometers—is complex and varied spatially. This necessitates identifying different regions of similar seismicity. In this study we attempt to identify and characterize regional seismic source zones based on a homogeneous catalog of earthquakes in and around India from 250 BC until 2010. We identified different regional seismic source zones and created separate catalogs for each respective zone. Most earthquake catalogs do not report earthquake magnitudes consistently over time, which may hinder defining seismicity patterns or assessing seismic hazards. The magnitude scales used for earthquake catalogs in India are not homogeneous. Compiling a complete catalog of earthquakes with uniform magnitudes is essential for defining seismicity patterns and assessing seismic hazards for a region (Chen and Tsai 2008). Hence the original magnitudes of earthquakes have to be converted to a common and reliable magnitude scale using appropriate magnitude correlations. In the raw catalog, many events can be dependent events that occurred in association with a mainshock in a cluster. These aftershocks and foreshocks have to be removed from the catalog using …