Hypocenter relocation and velocity model for major earthquakes in northwest Himalaya

Abstract

The proper understanding of earthquake geometry and location is very important to understand the seismicity of an area. In the present study, 185 earthquakes that occurred in the northwest Himalaya of magnitude Mw > 0.6 between 2010 and 2013 were relocated using the Modified Joint Hypocenter Determination method. After examining seven velocity models, average VP/VS ~ 1.73 computed by Wadati diagram is used to improve the hypocenter locations of the earthquakes. Based on hypocentral distributions, these earthquakes were classified into four groups. Group 1 is along the Punjal Thrust in Hazara Kashmir Syntaxes. Group 2 belongs to the Indus-Kohistan Seismic Zone whereas group 3 is along the Besham dome and the fourth group is along the Main Mantle Thrust. Shallow crustal earthquakes were relocated to 0–50 km, deep earthquakes were relocated to 50–100 km, and much deep earthquakes were relocated to 250–350 km depth. This analysis will be helpful to understand the seismicity of the northwest Himalaya of Pakistan.