Crustal Structure Beneath the Kumaon Himalaya and Its Linkage with Local Seismicity

Session: Seismic Imaging of Fault Zones [Poster]
Type: Poster
Date: 4/29/2020
Time: 08:00 AM
Room: Ballroom
Description: 

Subsurface of the Kumaon Himalaya has been studied using P-wave Receiver Function (RF) analysis of teleseismic earthquakes recorded by 18 broadband seismological (BBS) stations. H-k stacking of these RF’s reveal contrastingly low and high Poisson’s ratio values in the outer and inner Lesser Himalaya respectively. Both H-k stacking as well as 1-D RF inversion models reveal crustal thickness of ~38 km near HFT to ~42 km in the VT region suggesting a near-flat Moho. Common Conversion Point (CCP) stacking of RF’s along the Kali River profile demarcates prominent low velocity zone (LVZ) in the lower crust around the MCT. This is also supported by 1-D S-wave inversion models obtained from the regional BBS stations around Chiplakot Crystalline Belt (CCB). LVZ and high σ suggests partial melt in the lower crust around the CCB, which is coincident with a cluster of micro-to-moderate magnitude earthquakes at shallow to mid-crustal depths. Focal mechanism of local earthquakes recorded in the time span 2016-2018 are computed in an attempt to understand the seismo-tectonics of the area. These local earthquakes are mostly associated with the MHT, which shows variation in dip as we move from south to north. Presence of fluid influences the rheological property and controls the mechanical and shear strength of crustal rocks, producing the cluster of seismicity around the CCB.

Presenting Author: Somak Hazra

Authors