Subsurface identification using active MASW survey : Resolution of dispersion image

Abstract

Multichannel Analysis of Surface Waves (MASW)’ is a non-destructive field seismic survey method used for the identification of soil stratification. The three primary steps of MASW survey comprise field data acquisition, dispersion analysis and inversion analysis. During data acquisition, the vibration signatures generated by active or passive sources are recorded by a series of geophone receivers arranged in a predefined array. In the dispersion analysis, the collected wavefield are further processed to obtain the unimodal or multimodal dispersion trends represented by the frequency-phase velocity relationships. The dispersion curve is further processed through the inversion analysis to obtain the shear wave velocity profile of the substrata in 1-D, 2-D or 3-D formats. The resolution of dispersion image plays a crucial role in governing the accuracy and reliability of the outcome. Resolution gets affected by several parameters related to data acquisition and data pre-processing. Further, a good resolution dispersion image aids in unambiguous identification of the dispersion curve which is the prime requirement for the inversion analysis. Incorrect identification of the dispersion curve will lead to erroneous subsurface stratification.