Mudslide-bedrock Interaction at Super-Sauze (French Alps) by UAV-based Remote Sensing and Nanoseismic Monitoring

Abstract

The Super-Sauze (French Alps) mudslide was observed by high-resolution aerial photography from UAV (unmanned Aerial Vecicle) and Nanoseismic Monitoring in 2008. Remote sensing could resolve mudslide movement, and different types of superficial fissure patterns. Nanoseismic Monitoring identified seismic event types of ‘rockfall’, ‘fracture’ and ‘scratch’. The spatial distribution of the 'fracture' epicenters and ‘scratch’ source areas indicate the generation of these events close to the 'in-situ' crests of bedrock topography, most of them hidden below the mudslide material today. Seismic source areas correlate to the spatial distribution of observed fissure patterns which diverse into extension and shear fissures of varying size, and to secondary scarps. The superficial fissure patterns reside at stable position despite the moving mudslide; their spatial distribution, dimension, shape and orientation relates directly to the in-situ crests and the lateral bedrock boundaries. Our hypothesis from joint analysis of both observation data is that ‘fracture’ impulses are induced by brittle failure of the uppermost, dried mud layer, while ‘scratch’ sequences are initiated by “scratching” and “grinding” of single rock particles within the mudslide against the hard rock in-situ crests.