The Seismic Tra c Footprint: Tracking Trains, Aircraft and Cars Seismically

This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to di↵erences between this version and the Although naturally occurring vibrations have proven useful to probe the subsurface, the vibrations caused by trac have not been explored much. Such data, however, are less sensitive to weather and low visibility compared to some common out-of-road trac sensing systems. We study trac generated seismic noise measured by an array of 5200 geophones that covered a 7⇥10 km area in Long Beach (California, US) with a receiver spacing of 100 m. This allows us to look into urban vibrations below the resolution of a typical city block. The spatiotemporal structure of the anthropogenic seismic noise intensity reveals the Blue Line Metro train activity, departing and landing aircraft in Long Beach Airport and their acceleration, and gives clues about trac movement along the I-405 highway at night. As low-cost, stand-alone seismic sensors are becoming more common, these findings indicate that seismic data may be useful for trac monitoring.