Extracting Dispersion Spectrum Directly From the High-Speed Train-Induced Seismic Signal

The moving high-speed train (HST) generates strong vibrations in the railway roadbed, causing seismic waves to propagate through the subsurface medium. Consequently, moving HSTs can be considered as a novel seismic source for probing subsurface structures near high-speed railways (HSRs). An HST has several carriages, making it a typical combined moving source that induces a complex interference wavefield. Seismic interferometry (SI) is a commonly used method for generating virtual shot gathers based on background noise, and the phase-shifting method (PS) is commonly used to generate a dispersion spectrum based on the constructed virtual shot gathers. Therefore, SI and PS have been used for constructing virtual shot gathers and further generating the dispersion spectrum in HST-induced seismic signal processing. Although the HST-induced seismic wavefield exhibits complex interference features, it still maintains stable and strong amplitude characteristics. Therefore, we propose a method for directly extracting the dispersion spectrum from the HST-induced seismic signal through time-frequency decomposition and similarity-based velocity scanning. Compared to the commonly used procedure (SI + PS), the proposed method avoids the virtual shot gather construction procedure. The synthetic data example and real data example have shown the proposed method's effectiveness.