Multichannel Analysis-constrained Full Waveform Inversion of Surface Waves

Surface wave exploration is a crucial method in near-surface geophysical exploration. However, constrained by the assumption of horizontal layered models, traditional Multichannel Analysis of Surface Waves (MASW) and Multichannel Analysis of Love Waves (MALW) based on dispersion curve inversion often fails to yield accurate inversion results in complex geological settings. Full Waveform Inversion (FWI) of surface waves, which does not rely on the horizontal layered medium assumption, can enhance the accuracy of surface wave exploration in complex geological structures by directly fitting waveform data to invert for subsurface shear wave velocities. Despite its advantages, the highly nonlinear nature of FWI, along with its sensitivity to the initial model, presents significant challenges in practical applications. This study proposes a novel method for surface wave FWI constrained by the results of MALW. Initially, the inversion results from MALW are used to construct a prior constraint model. Based on this model, a new inversion objective function and gradient computation formula are developed for FWI. By integrating existing FWI techniques, this approach enables accurate inversion of complex subsurface structures. The proposed algorithm reduces the nonlinearity inherent in surface wave FWI, guiding the inversion process toward a more reliable solution. Numerical experiments demonstrate that, under identical initial model conditions, the proposed method outperforms existing surface wave FWI techniques in terms of both efficiency and accuracy.