Near-surface shear-wave velocity estimation based on surface-wave inversion

Abstract

Rayleigh waves always coexist with reflection waves in land seismic exploration. Many previous works have shown the value of Rayleigh waves in obtaining near-surface shear velocity, however, few of them show successful applications from exploration geophysics. With an aim of practical application of Rayleigh waves in exploration data, we discuss how to obtain an accurate and high-resolution dispersion curve, the inversion algorithm, and the comparison of velocity estimated from Rayleigh-wave inversion with refraction interpretation and tomographic inversion. We first analyze the resolution difference of f-v spectra calculated through f-k, τ-p, and phase-shift approaches and propose a two-step spectrum normalization scheme for accurate picking of the dispersion curve. We then adopt the weighted damped least-squares method as the inversion algorithm and find through synthetic data that the estimated shear velocity based on the algorithm is quite accurate and the inversion algorithm is fast and robust. Finally, we select seismic data from one land exploration project in China as an example for test, and find the inverted velocity from Rayleigh-wave dispersion has a good correlation with refraction interpretation and tomographic inversion.