Seismicity and focal mechanism of some recent earthquakes in North-east India and neighbourhood

Abstract

The seismicity of northeast India has been studied in the<br />light of the known geotectonic features based on the data from 1881 to 1972.<br />Now focal mechanism solutions of earthquakes using double couple hypothesis<br />have been discussed with reference to the plate theory of global tectonics<br />and the geological faults.<br />It was found that the constant b in Gutenberg-Ricliter's frequency<br />magnitude relationship was nearly I for both the periods of observations<br />namely 1920-1972 and 1963-1972 which was in agreement with the other<br />highly seismic regions of the world. Most of the new fault plane solutions<br />show significant strike slip movements with thrust faulting in this region.<br />Near the main boundary fault in northeast Himalaya, the pressures are<br />oriented almost along the strike of the fault while along the Manipur-Burina<br />border region, the pressures are acting at right angles or at acute angles to<br />the mountains and are shallow dipping.