Extraction of Rayleigh, Love, and Virtual Refraction Waves From 3C High-Speed-Train-Induced Vibrations for Near-Surface Characterization

Train traffic has been realized as a powerful seismic source for imaging and monitoring the shallow subsurface. High-speed trains running on viaducts generate seismic waves through bridge piers. The sources at bridge piers with a moving train are correlated in space and time. In this study, we extract Rayleigh, Love, and virtual refraction P-waves by applying seismic interferometry to high-speed-train-induced vibrations for near-surface characterization. We use cross coherence instead of cross correlation to eliminate the spurious imprint of source self-correlations. Stationary-phase analysis suggests that it is easier to retrieve direct and refracted waves using a linear array along the railway with a moving train source. In the experiment, we deployed a three-component (3C) “T” shape nodal array consisting of one linear array along the railway and the other one approximately perpendicular to the railway. With totally nine high-speed train events and by using stationary-phase segment selection, we extract strong multicomponent Rayleigh waves in the range of 3–20 Hz. We clearly retrieve the virtual refraction P-waves in range of 20–25 Hz using the in-line linear array and 25–35 Hz using the out-of-line array. Love waves in the range of 3–20 Hz are also observed. The extracted Rayleigh, Love, and virtual refraction waves are used to estimate S- and P-wave velocities of subsurface down to a depth of about 100 m. This study is the first 3C surface and body wave reconstruction and application for near-surface characterization from high-speed-train-induced vibrations.