A Study of Infrasonic Signals of Debris flows

Abstract

Mass movements such as debris flows, rock fall and snow avalanches are sources of subaudible sounds in the low frequency infrasonic and seismic spectrum. Recent studies indicated that debris flow-generated signals are of signi cant amplitude and occupy a relatively noise free band in the low frequency acoustic spectrum. Infrasound signals have the ability to propagate kilometres from the source, thereby allow monitoring of mass movements from a remote location. This study presents debris flow monitoring at four international sites - Lattenbach, Tyrol (Austria), Illgraben, Valais (Switzerland), and the MiDui and GuXiang Glacier, Tibet (China). The infrasound sensors used were the Chinese sensor (DFW I-III) or the German sensor (Gefell WME 960 H). The results show that debris flows emit detectable low frequency infrasonic signals (1-20 Hz) that are correlated to seismic signals. The infrasound sensors detect the phenomena before it reaches the sensors, depending on the landscape, distances and the sensitivity of the equipment.