Accurate Reconstruction of Shallow P-wave Velocity Model with Time-windowed Elastic Full-waveform Inversion

This study presents advances in the elastic multi-parameter full-waveform inversion (FWI) for shallow seismic applications. Rayleigh waves allow the reconstruction of the S-wave structure of the subsurface, whereas refracted P-waves can be used to determine the P-wave velocity. Studies that investigate the upper meters of the subsurface had shown that the amplitudes of Rayleigh waves are much higher than the amplitudes of P-waves. Consequently, FWI fails to reconstruct the correct P-wave velocity model due to its minor dependence on Rayleigh waves which dominate the misfit. We suggest a time-windowed strategy to have higher weight of refracted energy in the early stages of FWI while gradually lowering the weight throughout the inversion process. In a synthetic study we evaluate the performance of our approach and show that it is able to reconstruct the shallow P-wave velocity more accurately and to obtain a good fit of the first arrivals. A better resolved P-wave model then also allows FWI to achieve an improved resolution of the shallow S- wave velocity and density structure.