Multi Geometry Approach For Masw Survey

Abstract

The effect of source offset distance and the geophone array length on the dispersion curves are discussed in this paper. The source offset distance was changed systematically at sites with various subsurface conditions to investigate its effect on quality of data and the corresponding dispersion curves. Further, tests were carried out at same locations with various geophone intervals to evaluate the effect of the array length on the quality of the data and dispersion curves. Active and passive data were collected and the dispersion images were combined for possible improvement in dispersion image with enhanced multimodal delineation over a broadened bandwidth. It is observed that source offsets in the range of 25% to 45% of the array length provide dispersion curves with reasonable quality. Further, collecting data with different geophone intervals (same array mid station) improves the resolution of the obtained dispersion image. Multi geometry technique is suggested to obtain better quality field data. In this approach two (or more) different geophone intervals are used with same mid station. Passive and active data at two or more offset distances are collected for each of the array geometries. Stacking the obtained dispersion images can also result in a better quality dispersion curve.