Joint Inversion of Multimodal Attenuation and Dispersion of Surface Waves

The surface wave method, such as Rayleigh wave method or Love wave method, is an appealing noninvasive tool for delineating the interior structures of solid Earth and has been widely applied in near-surface geophysical exploration and regional or global seismology. The propagation of surface waves is directly related to the material property of solid Earth, which has been extensively recognized as the viscoelastic medium. In the viscoelastic layered media, the different frequency components of surface waves not only propagate with different phase velocities due to their dispersion property but also undergo different amplitude attenuations with the increasing offset because of their attenuation characteristic. Generally, the subsurface S-wave velocity structure can be estimated by using the phase information of surface waves, while the subsurface S-wave quality-factor structure can be investigated by applying the amplitude information of surface waves. In this study, based on the generalized reflection and transmission method, we firstly simulate the surface waves propagating in the viscoelastic layered half-space models and analyze the attenuation and dispersion characteristics of surface waves. Then, we compare the sensitivity of both attenuation coefficient and phase velocity with respect to the velocity and quality factor of S waves, the velocity and quality factor of P waves, and the mass density. Finally, considering the complex wavenumber of surface waves and using the Levenberg-Marquardt and singular-value decomposition techniques, we conduct the joint inversion of multimodal attenuation coefficient and phase-velocity dispersion curves to estimate the velocity and quality factor profiles of S waves simultaneously.