A new method for estimation of Rayleigh wave group velocity spectrum

Shear-wave velocity is commonly used to understand the characteristics of the subsurface, which can be retrieved by inverting the phase or group velocity in Rayleigh wave surveys. Now, many studies have shown the advantage of analyzing group velocity over phase velocity to obtain the S-wave velocity. However, previous methods often suffer from poor resolution in estimating group velocity. In order to improve the resolution of the group velocity and reduce uncertainty in extracting dispersion curves, we propose a new method for estimation of the Rayleigh wave group velocity spectrum based on the slant stack and adaptive generalized S-transform with energy reassignment. This method incorporates the adaptive generalized S-transform and the energy reassignment technique to enhance the time-frequency representation, and then calculates the group velocity at each frequency using the slant stack. By conducting experiments with synthetic seismic records, it is evident that the new method has high resolution and accurate multimode group velocity calculations. Furthermore, when applied to a field dataset and synthetic record with noise, the method shows better results and noise robustness. This confirms the superior performance of the method at generating high-resolution dispersion images of the group velocity compared to previous approaches. The method will become an efficient tool in Rayleigh wave exploration.