Slidequake Generation at Softrock-landslides

Our study describes the conditions for the generation of initial fracture processes, i.e. slidequakes, at three different creeping softrock-landslides: the Slumgullion landslide in the San Juan Mountains, Colorado, USA, the Heumoes slope in the Austrian Alps, and the mudslide in Super-Sauze, French Alps. Our investigations identified seismic and aseismic slip in each slide, with slidequakes focusing at significant bedrock structures or at lateral boundaries. At the Slumgullion landslide, the majority of slidequakes occurred at the lateral boundaries of the landslide, while no events were detected along the planar basal surface. At Heumoes slope, the slidequakes cluster in the slope area with the lowest surface displacement rates. A significant bedrock rise, oriented perpendicular to the direction of slope movement, divides the landslide geometry in two basins, and probably impedes motion, slows the slide, and leads to slidequakes. At the Super-Sauze mudslide, the slidequakes are preferentially generated in its centre where the deformation rates are highest. There, the slidequake generation is directly linked to in-situ bedrock crests that border several gullies oriented in line to direction of the entire slope movement. Synoptic comparison of these three scenarios underlines the importance of landslide-bedrock and landslide-lateral boundary interactions under gravitational loading.