On the Retrievability of Seismic Waves From High-Speed-Train-Induced Vibrations Using Seismic Interferometry

High-speed train (HST) generates strong and repeatable vibrations that could be used for subsurface imaging and monitoring. Compared with other ambient noise, HST vibrations are generated by a moving source and have striking characteristics as a deterministic source. However, little attention has been paid to the effects of the characteristics of HST sources on the seismic wave retrieval using seismic interferometry. The aim of this study is to investigate what types of seismic waves are retrievable by applying seismic interferometry to HST-induced vibrations. By analyzing the cross correlation of the HST-induced vibrations between two receivers, we find that cross terms are introduced during the cross correlation. These cross terms are nonnegligible for reflection-wave retrieval but can be negligible for the retrieval of direct waves, scattered waves, and refraction waves. This finding has been validated by field data tests. We further demonstrate that the retrieved surface waves can be used to estimate near-surface velocities and that the retrieved scattered surface waves can be used to locate near-surface heterogeneous bodies.