Rockfall alarm system for railway monitoring: integrating seismic detection, localization and characterization

Rockfalls pose a threat to human infrastructure below cliffs. Sensitive and reactive alarm systems are needed for rail traffic safety, as small rockfalls (≈ 0.01 m 3 ) impacting the rail may cause train derailment. We propose to use seismic processing for rockfall early warning, powered by dense arrays deployed along the track. The method is evaluated by dropping rocks from a controlled height and triggering rockfalls on a cliff. We show that seismic arrays are highly sensitive to small impacts, and are able to detect them, locate them, and estimate their magnitude. The detection can be performed in near real-time with a simple algorithm, as small-scale rockfalls produce impulsive waveforms near the impact. Precise localization with Matched Field Processing is able to track the trajectory of a rockfall. Impacts against a rail might be recognized by their source signature. The seismic amplitudes are related to the rockfall volume by the Hertz law, which may be used to estimate their volume. These results show the potential of seismic-driven near real-time rockfall alarm systems.