Seismicity of the Himalaya and the northeast India, and nature of continent-continent collision

Abstract

The Himalaya together with the Arakan-Yoma forms a well defined arc to the north and east of the Indian Peninsula. The seismicity along the Himalayan arc is attributable mostly to the collision between the Indian and the Eurasian plates, and along the eastern margin to the subduction of the Indian plate underneath the Arakan-Yoma. Along the Himalayan arc several thrusts (including the Main Boundary Thrust, the Main Central Thrust) and transverse lineaments appear to be active. Analysis of focal mechanisms reveals that although thrust movements are predominant along the Himalayan arc, normal and strike-slip faulting is also taking place along some of the transverse lineaments. Underneath the Arakan-Yoma/Burmese plains, strike-slip faulting is also active in addition to the thrusting. Orientation of P axes for all thrust solutions changes sharply from predominantly east-west along the Burmese arc to NS and NE-SW along the Himalayan arc. Models of plate underthrusting along the Himalayan front based on seismicity are presented. It is suggested that the effects of continent-continent collision are recorded over a very large area including China, Hindukush, N Pamir and S Tien Shan.