Enhanced Scholte-wave characterization of marine sediments through dispersion-spectrum McMC inversion

SUMMARY This study proposes a dispersion-spectrum inversion method for improved estimation of shear-velocity (VS) profiles in marine sediments using underwater multichannel analysis of surface waves (UMASW). The method leverages an efficient forward modelling algorithm combined with a Markov chain Monte Carlo (McMC) global search to address the nonlinearity inherent in the inversion process. Comparisons with field and synthetic data demonstrate that the VS profiles inverted using the full dispersion spectrum (in terms of the frequency-phase velocity spectrum, FVS) exhibit greater stability and reliability than those obtained through traditional fundamental-mode (FM) inversion. Pseudo 2-D VS profiles are constructed by interpolating 1-D profiles obtained from the FVS-McMC inversion, showing more continuous subsurface interfaces that align with borehole data. Parametric studies further highlight the influence of Poisson’s ratio, water layer thickness and VS contrast on the dispersion behaviour, underscoring the robustness of the proposed approach for offshore site characterization.