Seismic monitoring of rockfalls, slide quakes, and fissure development at the Super-Sauze mudslide, French Alps

Applying the method nanoseismic monitoring to the fast-moving mudslide in Super-Sauze (French Alps) we observed different types of seismic events caused by varying slope dynamics. We identified signals caused by rockfalls in the source area of the slope, and different types of signals, which had obviously been generated by material failure within the unstable part of the mudslide. Signal analysis and further investigations, e.g. the analysis of magnitude–frequency distribution and simultaneous measurements by nanoseismic monitoring and extensometer devices, revealed the generation of the observed seismic signals: fracture processes, i.e. slide quakes, within the unstable sediments and the development of fissures at the slope's surface. The spatial distribution of the epicenters (slide quakes), respectively the estimated source area (fissure development), correlates well with parts of the slope moving with higher velocities at the surface. Most of these signals were generated close to the in-situ crests, which are mostly covered by the mudslide material today, indicating specific dynamics in these particular slope areas.