Effect of Source Characteristics on the Resolution of Dispersion Image from Active MASW Survey

Abstract

In order to obtain a reliable shear wave velocity profile from an active MASW survey, it is important to develop a good-resolution dispersion image. In this regard, this article describes the effect of source characteristics on the quality of the recorded wavefield, and hence, on the resolution of the obtained dispersion image. Active MASW survey is conducted at three locations at IIT Guwahati campus, having different substrata characteristics based on the variation of stiffness. Based on the dispersion image, averaged power spectrum and the shear wave velocity profiles, it is understood that owing to substrata heterogeneities, proposing a universal guideline for conducting active MASW survey is extremely difficult. To obtain a good-resolution image, it is suggested to conduct the surveys with heavier sources to obtain good-resolution dispersion images yielding deeper strata information. Lighter sources, if used, should be accompanied by appropriate stacking of the dispersion images to enhance or strengthen the resolution of the dispersion images, even at the low frequencies. It is also suggested that proper material should be used as base plate/striker plate for active MASW survey depending upon the target depth and feasibility of the investigation.