Estimation of Body Wave (P and S) Velocities and Depth to Bedrock by Refraction Seismic and MASW Studies in an Earth Quake Prone Region

DOI: 10.5176/2251-3361_GEOS12.93

Authors: T. Seshunarayana and N. Sundararajan

Abstract:
Refraction seismic surveys and multichannel analysis of surface waves (MASW) were carried out simultaneously to estimate the depth to bedrock in addition to P-wave and S-wave velocity variations in the subsurface in an area (Jabalpur, India) which was damaged by a moderate earth quake during 1967. The results of as many as 116 test sites spread over different geological units indicate the bedrock depth to be the same while the variations in P-wave and S-wave velocities are quite interesting. The S-wave velocity presented here is harmonic velocity up to a depth of 30m. The fact that the shear wave velocity by and large is more than 200m/sec except a few sites where it is marginally less than 200m/sec even in alluvium has a bare minimum liquefaction hazard. The results of selected sites from all geological units are presented here as a case study.
Keywords: MASW; body waves; bedrock depth, liquefaction