Seismic Monitoring of Slope Dynamics Caused by the Mudslide at Super-Sauze in the Southern French Alps

In this study, we describe the application of Nanoseismic Monitoring to the fast moving mudslide at Super-Sauze in the southern French Alps. The unstable slope mainly consists of marls and shows an immense dynamic behaviour with velocities of more than 3 cm/day. During a 10 days field campaign in July 2008, we were able to detect and locate different signals (type ‘A’ – ‘C’) caused by the movement of the mudslide. While the events type ‘A’ are caused by rockfalls in the source area of the slope, we could identify different types of signals (type ‘B’ and ‘C’), which have been obviously generated by material failure within the unstable sediments. The spatial distribution of the epicenters (type ‘B’), respectively the estimated source area (type ‘C’), correlates well with parts of the slope moving with higher velocities. Most of these signals have been generated close to the “in-situ crests”, which are covered by the mudslide material today. Our preliminary assumption is that the events of type ‘B’ are generated by impulsive fractures within the sliding material, while the events of type ‘C’ are caused by by “scratching” and “grinding” at the boundary between the sliding material and the bedrock.