Extraction of Rayleigh, Love, and Virtual Refraction Waves From 3C High-Speed-Train-Induced Vibrations for Near-Surface Characterization
Binbin Mi, Jianghai Xia
Abstract
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 crosscoherence instead of crosscorrelation 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 9 high-speed train events and by using stationary-phase segment selection, we extract strong multicomponent Rayleigh waves in 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 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.