Oral Presentation

A SCHEMATIC MODEL TO EXPLAIN INTRAPLATE SEISMICITY IN THE GODAVARI BASIN IN PENINSULAR INDIA

Abhijit Gangopadhyay, Pradeep Talwani, Department of Geological Sciences, University of South Carolina, 701 Sumter Street, EWSC Room #501, Columbia, South Carolina, 29208, ( Email: abhijit@prithvi.seis.sc.edu).

In order to explain seismicity in Stable Continental Interiors, we examined different intraplate regions around the world. One example of an intraplate setting is the Godavari Basin in the eastern part of Peninsular India which is the location of the mb = 5.3 Bhadrachalam earthquake of April 13, 1969. Analysis of geophysical and geological data show that the Godavari Basin is a NW SE striking Mesozoic rift structure with a length of about 800 km and width of about 100 km. It is occupied mainly by Proterozoic and Permian Jurassic rocks bounded by normal faults and has shown periodic activity since the Middle Proterozoic. No significant major earthquakes have occurred in the last two hundred years but occasional seismic activity have been reported both from within the rift valley and along its margins. The region is characterized by NNE ENE oriented SHmax. Gravity data indicate a central Bouguer gravity low over the basin with a break along an east west trend near Bhadrachalam and with steep gradients to the east of this low extending along the whole length of the rift valley. The east west feature has been identified as a deep seated fault and the steep gradients have been attributed to the master fault of the Godavari rift valley. The epicenter of the Bhadrachalam earthquake lies very near to the intersection of this master fault and the EW trending fault. Gravity highs are also observed along the edges of the rift valley and these have been attributed to large scale basic intrusions. Our schematic model to explain these observations is that the rift zone provides a suitable weak zone for localized stress build up and intersecting faults and buried plutons act as stress concentrators for localization of seismicity.

This is a student paper.