Sensitivity analysis of surface wave dispersion curves for various subsurface parameters
Luping Qu, Kristopher A. H. Innanen, Jan Dettmer
The propagator matrix method is commonly used for inverting near-surface shear-wave velocity. An important precondition for its feasibility is the different sensitivity levels of dispersion curves with respect to shear-wave velocity, primary-wave velocity, layer thicknesses, and density. Here, we analyze the sensitivity of surface-wave dispersion-curves at different frequencies for various subsurface parameters. Not only the fundamental mode, but higher-order modes extending to the fourth higher-order mode are all included in this study. From the analysis, higher modes are more sensitive to parameters in the deeper area. Besides, the sensitivity analysis is conducted on the phase-velocity, the group velocity, and their derivatives, respectively. Through comparing various types of observing data, the phase velocity derivative is more sensitive to parameter perturbations in the same wavelength range. However, its sensitivity shows simultaneously positivity and negativity at different depths. While the phase velocity shows positivity exclusively. At last, inversion stability and accuracy of different types of observing data are discussed.