Development of an acoustic monitoring system for natural mass movements

Rapid mass movements such as avalanches, debris flows and rock fall are periodic or episodic phenomena that occur in alpine regions. Despite the increase in research carried out in last decades in order to better understand these processes, many unknowns remain. This is partly due to the scarcity of observation data from real events. This project presents a new approach to event monitoring through the use of seismic and acoustic methods such as geophones and infrasound sensors. The benefits of acoustic methods include independence from weather conditions with regard to visibility, no structural need for sustainability and monitoring from a remote location unaffected by the event. Monitoring systems based on seismic signals are quite common and have been used to study avalanches and debris flows for many years. Various previous studies on debris flows and avalanches have already shown that it is possible to detect and monitor these processes with geophones and that it is possible to distinguish them from other seismic sources. To increase the reliability and minimize false alarms the emphasis lies on a combination with infrasonic sensors. Low frequency infrasound signals have the ability to propagate kilometres from the source of a mass movement and provide a basis for the development of wide area automated monitoring systems which can operate in locations unaffected by the process activity. Common used signal analysis methods for warning purposes use threshold values for the signal amplitude. In contrast this project focuses on frequency spectra to determine the characteristic frequency of the process and increase the warning reliability. The final goal is the development of a reliable monitoring system for natural hazards including monitoring hardware, analysing software and a database of characteristic signals.