Dispersion inversion for P- and S-wave velocities based on guided P and Scholte waves

Abstract

Inversion based on dispersion curves is widely used for the estimation of subsurface velocity structures. However, conventional surface-wave dispersion inversion usually uses normal modes, and only the S-wave velocities are retrieved. To retrieve P-wave velocities, the dispersion of guided P waves should be considered. We develop an inversion scheme that uses the guided-P-wave and Scholte-wave modes to implement an integrated inversion for P- and S-wave velocity structures of shallow marine sediments. The forward modeling of dispersion curves is based on the spectral-element method and the perfectly matched layer technique. A quantitative sensitivity analysis of guided P modes is then carried out, which not only confirms the capability of guided P modes for estimating the P-wave velocity but also indicates that guided P modes can be combined with Scholte modes to better constrain the S-wave velocity. Based on the Levenberg-Marquardt algorithm, a joint inversion scheme that uses guided P and Scholte modes is developed. The validity of the inversion scheme is assessed by testing synthetic and field ocean-bottom seismometer data obtained in shallow marine environments. The results demonstrate the effectiveness of the joint inversion for retrieving the P- and S-wave velocity structures of shallow marine sediments.