Seismotectonics of the Himalaya and its vicinity from centroid-moment tensor (CMT) solution of earthquakes

The centroid-moment tensor solutions of more than 300 earthquakes that occu rred in the Himalayas and its vicinity regions during the period of 1977-19 96 are examined. The resultant seismic moment tensor components of these ea rthquakes are estimated. The Burmese are region shows prominent eastwest co mpression and north-south extension with very little vertical extension. No rtheast India and Pamir-Hindu Kush regions show prominent vertical extensio n and east-west compression. The Indian plate is subducting eastward beneat h the northeast India and Burmese are regions. The overriding Burmese are h as overthrust horizontally with the underthrusting Indian plate at a depth of 20-80 km and below 80 km depth, it has merged with the Indian plate maki ng "Y" shape structure and as a result the aseismic zone has been formed in the region lying between 26 degrees N-28 degrees N and 91.5 degrees E-94 d egrees E at a depth of 10-50 km. Similarly, the Indian plate is underthrust ing in the western side beneath the Pamir-Hindu Kush region and the overrid ing Eurasian plate has overthrust it to form a "Y" shape structure at a dep th of 10-40 km and below 60 km depth, it has merged with the Indian plate a nd both the plates are subducting below 60-260 km depth. Further south, the overriding Eurasian prate has come in contact with the Indian plate at a d epth of 20-60 km beneath northwest India and Pakistan regions with left lat eral strike slip motion. (C) 2000 Elsevier Science Ltd. All rights reserved .