Rayleigh-wave tomography using traffic noise at Long Beach, CA

Abstract

Passive seismic arrays on land provide the opportunity to push the use of ambient noise cross-correlation techniques to frequencies well beyond the microseism band. Using data recorded by a dense array in Long Beach, California, we demonstrate that high-frequency (> 3 Hz) fundamental-and first-order-mode Rayleigh waves generated by traffic noise can be extracted from the ambient noise field and used for tomographic studies. Here, we show group velocity maps derived from travel times of the fundamental-mode Rayleigh waves at 3.00 Hz and 3.50 Hz. The velocity trends in our results correlate well with lithologies outlined in a geologic map of the survey region. As expected, less-consolidated materials display relatively low velocities, while more-consolidated materials display relatively high velocities.