Seismic interferometry from correlated sources by crosscoherence: Application to the retrieval of Rayleigh, Love and virtual refraction waves from 3C train-traffic-induced vibrations

We extract Rayleigh, Love, and virtual refraction P waves by applying seismic interferometry to high-speed-train-induced vibrations for near-surface characterization. The sources at bridge piers with a moving train are correlated in space and time. 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, 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. Love waves in range of 3-20 Hz are also observed. The extracted Rayleigh, Love and virtual refraction waves can be used to estimate S and P wave velocities of the shallow subsurface.