Seismic imaging of the crust beneath Garhwal Himalayas

Kumar, Nishant (2018) Seismic imaging of the crust beneath Garhwal Himalayas. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Nishant Kumar (13MS093)) 13MS093.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

In this study, we estimated the depth of Moho and velocity structure beneath fourteen three-component stations located in Garhwal Himalayas using receiver function followed by its inversion using non-linear direct search Neighbourhood Algorithm (NA). These 14 stations are oriented along SE-NE trend having a southernmost station located at Main Frontal Thrust (MFT) and northernmost station located at South Tibetan Detachment (STD) spanning 79 to 80° E. Teleseismic earthquakes recorded during 2011 and 2012 have been used for conducting this study. The inverted shear wave velocity models show crustal thickness variation from 36 to 44 km for Lower Himalayas and 46 to 52 km for Upper Himalayas. As a result, a slight dip is observed towards NE direction for the moho based upon preceding result. The aforementioned argument is further concretized by the fact for some stations we are getting different Ps arrival timing with varying backazimuth which in turn tells us about varying depth of moho observed from a different direction, which can only happen if there is anisotropy or if there is dipping structure or can be both of the above. The average crustal shear velocity in this region varies from 3.33 to 3.36 km/s. The average Vp/Vs ratio varies in this region from 1.7 to 1.8.

Actions (login required)

View Item