SUBSURFACE INVESTIGATION IN THAL REGION USING SHALLOW SEISMIC SURVEY

Abstract

Kuinaon Himalayas lie in the seismic zone V and therefore is prone to large seismic risks. Stress gets accumulated due to constant thrust between Eurasian plate and Indo-Australian plate. The Thai region, on which I worked on is prone to high seismic activities because of reason mentioned above. The main objective of this present work is to study site effects in Kumaon I-Iimalaya by using Multi Channel Analysis of Subsurface Wave method and using the same for the estimation of soil bed thickness. The Rayleigh type surface waves show dispersive characteristics which were utilized for imaging the shallow subsurface layers near Bageshwar, India. The reliability of MASW method depends on the accuracy of the determined phase velocities for horizontally traveling Rayleigh waves. Multichannel recording is useful in effective identification and isolation of noise. The multichannel record is decomposed into time-frequency format permitting real-time maximization of S/N ratio during processing stages. Using "Seisimager", the MASW data were processed and interpreted and I found that the shear wave velocity (Vs) is in the range of 300 —750 rn/sec covering a depth range of 30-40 m.