MULTICHANNEL ANALYSIS OF SURFACEWAVES

Abstract

Garhwal region lying in the Seismic V, in Himalayas is vulnerable to high seismic risks. Because of the constant thrust force underlying Indian plate and the Eurasian plate there is high accumulation of stress. Same reasons are also responsible for the high risk of having seismic activities in the region, Shivpuri and Bayasi, in which I worked. The main objective of my research is to study is to study the site effects in Garhwal region in Himalaya using MASW method and also to calculate the approximate bedrock thickness. The Rayleigh waves display dispersive characteristics which can be used for imaging the layers in the shallow-subsurface. The reliability of this method depends on the accuracy with which phase velocities were determined for Rayleigh waves traveling in horizontal direction. Here recordings in multiple channels becomes a key for efficient identification and reduction of noise.Now Multi-channel recordings are decomposed into frequency-time format which permits the real-time maximization Signal by noise (S/N) ratio during the processing steps. With the help of Seislmager Software, the MASW data further processed and then interpreted and thereby found that the velocity of the shear wave (Vs) is in the range of 200-450 m/s in the Bayasi region and 1300-200 m/s in Shivpuri region.