Seismicity of the Indian peninsular shield from regional earthquake data

In this comprehensive study of seismicity and seismotectonics of the penins ular Indian shield region, seismic data of regional earthquakes spanning tw o decades (1978-1997), obtained at Gauribidanur seismic array (India) and i ntegrated where necessary with data from other seismological stations in th e region, have been analyzed in detail. With a slow rate of stress accumula tion, the shield is found to have low to moderate seismicity that takes int o 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 s patio-temporal pattern of occurrences of the earthquakes combined with thei r magnitude and seismic energy distribution is consistent with the view tha t the peninsular seismicity is low to moderate and episodic in nature. Regi ons of moderate seismicity and its low-grade counterpart constituted by mic roearthquakes (magnitude less than 3), appear correlated to the areas trave rsed by known geologic faults and subfaults, shear zones, and other such te ctonic features. Microearthquakes represent about two-thirds of the total r egional seismic events during the past two decades.