Dispersion of Scholte Waves in Horizontally Layered VTI Media

Summary The dispersion of Scholte waves provides a fundamental basis for inverting shallow seafloor elastic parameters. With the expansion of marine exploration, an isotropic seabed approximation has become increasingly inadequate. Therefore, in this study, Scholte-wave dispersion was analyzed in vertically transversely isotropic (VTI) media and the sensitivities of key parameters were quantified. Using a reduced delta-matrix formulation, a numerically stable dispersion equation for fluid-solid-coupled VTI media was derived and validated with elastic wavefield modelling and frequency-velocity spectra. Sensitivity tests on three representative seabed models [velocity increasing with depth (VID), a low-velocity layer (LVL), and a high-velocity layer (HVL)] show that anisotropy amplifies phase-velocity sensitivity to P-wave velocity (VP), especially for higher modes. In contrast, sensitivities to Thomsen parameters ε and δ are secondary but non-negligible. As mode order increases, the sensitive frequency band broadens and penetrates to greater depths. For the HVL model, dispersion is particularly sensitive to the overburden above the high-velocity layer. By contrast, for the LVL model, sensitivity concentrates within the low-velocity layer itself and above it. These sensitivity patterns reflect the influences of different parameters on inversion results and support the development of dispersion curve inversion for anisotropic shallow seafloor.