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 occurred in the Himalayas and its vicinity regions during the period of 1977-1996 are examined. The resultant seismic moment tensor components of these earthquakes are estimated. The Burmese arc region shows prominent east-west compression and north-south extension with very little vertical extension. Northeast India and Pamir-Hindu Kush regions show prominent vertical extension and east-west compression. The Indian plate is subducting eastward beneath the northeast India and Burmese arc regions. The overriding Burmese arc has 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 making "Y" shape structure and as a result the aseismic zone has been formed in the region lying between 26°N-28°N and 91.5°E-94°E at a depth of 10-50 km. Similarly, the Indian plate is underthrusting in the western side beneath the Pamir-Hindu Kush region and the overriding Eurasian plate has overthrust it to form a "Y" shape structure at a depth of 10 -40 km and below 60 km depth, it has merged with the Indian plate and both the plates are subducting below 60-260 km depth. Further south, the overriding Eurasian plate has come in contact with the Indian plate at a depth of 20-60 km beneath northwest India and Pakistan regions with left lateral strike slip motion.