Research on Dispersion Curves of MASW

Abstract

The multichannel analysis of surface wave (MASW) method has been effectively used to determine near‐surface shear (S)‐wave velocity and map bedrock. Estimating the S‐wave velocity profile from Rayleigh‐wave measurements is straightforward. A three‐step process is required to obtain S‐wave velocity profiles: acquisition of a multiple number of multichannel records along a linear survey line by use of the roll‐along mode, extraction of dispersion curves of Rayleigh waves and inversion of dispersion curves for an S‐wave velocity profile for each shot gather. A pseudo‐2D S‐wave velocity section can be generated by aligning 1D S‐wave velocity models at the midpoint of each spread. This process implies that the extracted dispersion curve is only determined by the geophysical structure within the geophone spread and not affected by the source geophysical structure. In this paper, dispersion curves of synthetic dataset by fixing the receiver spread and changing the source location are calculated to testify the assumption of MASW. Results demonstrate that the dispersion curves are affected by the whole acquisition system including source and receiver spread structure.