Considerations for anisotropic surface-wave inversion

Near-surface characterization of elastic wave velocities is important for both the engineering and environmental geophysics community and for the geophysical exploration community. Surface-wave inversion is a common method used to estimate shear velocity at the shallow subsurface. Most common Rayleigh-wave inversions are carried out assuming a stratified media of homogenous isotropic layers and use propagator-matrix methods as the forward model operator. Still, in the shallow subsurface, vertical compaction can induce vertical transverse isotropy (VTI) in loose sediments. Rayleigh-wave phase velocity depends on four of the five VTI independent elastic parameters. Herein, we show the effect anisotropy has on the Rayleigh-wave dispersion curve. We also present model parameter uncertainty analysis of two proposed parameterizations for anisotropic VTI inversion. One parameterization is based on Thomsen's parameters and a second parameterization is based on the density normalized elastic tensor.