Abstract

Well-documented historical earthquake data from 1340 to 1983 has been analyzed and reported in this work so as to understand the seismicity and associated phenomena of Peninsular India. It has been the belief among earth scientists that the Peninsular Shield is aseismic, as the region attained stability long ago. However, the earthquake at Koyna (10 December 1967), Bhadrachalam (13 April 1969), Broach (23 March 1970), Hyderabad (30 June 1983) etc., altered this concept and it has now widely accepted that seismic activity is still continuing on a mild scale. As such, a need has arisen to take into consideration historical as well as recent seismological data to study the seismic status of Peninsular India.

Using the well-known ‘frequency-magnitude” relation of Gutenberg and Richter (1954), an attempt has been made to derive “a” and “b” and the ratio (a/b). The values as obtained for Peninsular India are 4.4, 0.85, and 5.17, which are typical of moderately active zones the world over. Recurrence periods of earthquake magnitude 6.75 and 7.0 are calculated to be 21 and 35 yr, respectively. Further, the historical seismicity correlates well with the protocontinents such as Dharwar, Aravalli, and Singhbhum in the Peninsular Shield. It is observed that seismicity in a broad sense is defined by the protocontinents with low intracontinental seismicity, while the lineaments and rift valleys are from zones of moderate seismicity.

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