Investigation of landquakes in the European Alps

Abstract

The use of seismic broadband networks has proven to be a useful tool to identify and characterise landslides. In this thesis, this approach is applied to rockfalls in the European Alps and evaluated for applicability and accuracy. An amount of 82 alpine landslides between 2009 -2019 have been investigated, which were reported by newspaper articles and previous studies. The events varied in all kind of landslide typologies like rockfall and debris flows and show event volumes between one and three million cubic metres. The seismic broadband network was selected to include 65 stations in operation during the whole period of analysis. The seismic data of the network got evaluated visually and by using an STA/LTA detector programmed in Matlab. A total of 25 (30.5%) rockfalls were successfully recorded using the selected seismic network - mainly large falling mass movements with a minimum recorded volume of 1’000 m3. The seismic network was not able to detect flowing mass movements. The analysis of seismic attenuation of landslide signals has shown that the density of the seismic network is a critical factor. In addition to volume, the detection of individual events depends mainly on the process of the mass movement. The impact of rock masses after a free-fall phase, for example, generates a much higher seismic energy compared to rock flowing on the surface.