Seismicity and tectonics of the Bay of Bengal: Evidence for intraplate deformation of the northern Indian plate

Seismicity and fault plane solutions of several earthquakes in the Bay of Bengal have been studied to focus attention on the nature of intraplate deformation in the northern Indian plate. A widely dispersed diffuse seismicity provides evidence that the intraplate region of the entire Bay of Bengal and peninsular India of the Indian plate are seismically active of which the Gangetic delta and the eastern flank of the Ninety East Ridge show somewhat higher seismicity in comparison to the thickly populated epicenters at the eastern plate boundary. Predominance of thrust faulting earthquake mechanisms with consistent north-dipping fault planes and more or less N-S pressure axes imply that N-S compression is more prevalent in the intraplate region of the Bay of Bengal which is analogous to the Himalayan are. This intraplate seismicity and N-S compressive deformation is presumed to be the result of collisional resistance to the north moving Indian plate with the Eurasian plate at the Himalayas where subduction of the Indian lithosphere in mantle has stopped recently. As a result, to compensate the horizontal compressive force by ridge-push at the Carlsberg Ridge, the intraplate region of the northern Indian plate in continuation to the Central Indian Ocean Basin no longer remains passive due to a strong repulsive force at the collisonal plate boundary Himalaya that causes stress transmission towards south and makes the intraplate region seismically active.