Application of Inversion Method With F-K Spectrum as Objective Function in High-Speed Train Seismic Data

As a new type of seismic source, the high-speed train (HST) seismic source has great application potential in subsurface imaging in terms of high intensity, strong repeatability, and wide distribution compared with traditional seismic sources. However, the HST seismic data are severely interfered in the time-space domain due to the complex mobile combination source. Besides, the body waves are almost swamped by strong surface waves. Therefore, it is difficult to directly use this kind of seismic data for subsurface exploration. Considering the characteristic differences between the surface and body waves in the frequency-wavenumber (F-K) domain, it is more conducive to separate the surface and body waves for the HST seismic data in the F-K domain, so as to use different wavefield information in sequence. Therefore, in this study, we attempt to apply the inversion method with F-K spectrum as the objective function to HST seismic data, which aim to more effectively utilize the surface and body waves therein. In addition, to alleviate the coupling effect between P-wave and S-wave in elastic waveform inversion, we introduce the divided-offset strategy to further improve the quality of the inverted P-wave and S-wave velocities. Numerical experiments indicate that the proposed inversion method is beneficial to make better use of the surface and body waves in HST seismic data and is expected to provide more insights on the use of HST seismic data for subsurface monitoring and detection.