Seismicity of the Indian Peninsular Shield from Regional Earthquake Data

In this comprehensive study of seismicity and seismotectonics of the peninsular Indian shield region, seismic data of regional earthquakes spanning two decades (1978–1997), obtained at Gauribidanur seismic array (India) and integrated where necessary with data from other seismological stations in the region, have been analyzed in detail. With a slow rate of stress accumulation, the shield is found to have low to moderate seismicity that takes into account a couple of earthquakes of magnitude slightly larger than 6. The frequency-magnitude analysis of the data set gives a b value of 1.18. The spatio-temporal pattern of occurrences of the earthquakes combined with their magnitude and seismic energy distribution is consistent with the view that the peninsular seismicity is low to moderate and episodic in nature. Regions of moderate seismicity and its low-grade counterpart constituted by microearthquakes (magnitude less than 3), appear correlated to the areas traversed by known geologic faults and subfaults, shear zones, and other such tectonic features. Microearthquakes represent about two-thirds of the total regional seismic events during the past two decades.