High-resolution velocity structure across HFT, Kumaon Himalaya using controlled-source seismic data sets

Abstract

The present study carried out in the vicinity of Himalayas lying in the Seismic Zone V, with an objective to estimate the high-resolution shallow subsurface structure across Himalayan Frontal Thrust (HFT). To fulfill the objective, we have used a seismic Thumper as an energy source and 96 geophones (natural frequency 5 HZ) to record the energy over a 5.2 km long profile. We have applied the Traveltime Tomography (TTT) of refracted phases to estimate the smooth shallow subsurface velocity-depth model. The Obtained 2D velocity model down to a depth of 400-500 m shows layered sediment in which top 100 m sediment shows a very low velocity ranging between 1.2 - 1.6 km/s indicating the weathered layer caused by eroding agent - River Dabka and Baur. The gradual increase in the velocity with depth indicating the compact sedimentary rocks and the velocity range of 2.2 – 3 km/s are in good agreement with the velocity of sandstone and Siwalik rocks found in the region.