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 (HSR). 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 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 the time-frequency decomposition and the 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.