oa Multimodal Rayleigh Wave Dispersion Curve Picking and Inversion to Build Near Surface Shear Wave Velocity Models

The use of Rayleigh waves to invert for a near surface shear wave velocity model is attractive in converted wave processing, such as the application of receiver side statics correction and PS PSDM. We propose a differential evolution inversion scheme to invert Rayleigh wave dispersion curves, and we apply it on a field dataset with high density acquisition to obtain the underlying shear wave velocity structure. The joint use of a new misfit function, which allows multimodal inversion and reduces the risk of mode misinterpretations, combined with differential evolution inversion is highly likely to converge to the real shallow shear wave velocity structure. A semi-automatic picking method based on the quick thinning algorithm is introduced to extract the dispersion curves from frequency-phase velocity spectra. This greatly reduces the demand on manual labor and improves productivity.