Linking Sub-surface Slidequakes to Superficial Fissure Growth and Displacement Analysis: The Super-Sauze Mudslide Field Campaign 2010

Applying passive seismic analysis techniques realized by Nanoseismic Monitoring at creeping to slow-moving, soft-rock landslides in the Alps, we observed fracture processes of slope material, also called slidequakes. Their time-frequency signature resembles impulsive signals from local earthquakes, and indicates brittle fracturing of slope material. We could locate slidequakes within tens to hundreds meters off our stations, and determine Ml between −3 and −1. Slidequakes are very weak signals with poor signal-to-noise ratio (SNR); thus neither precise depths nor moment tensor solutions could be derived. At Super-Sauze two further event types were observed (I) caused by rockfall impacts, and (II) resembling non-impulsive, reverberant ETS (episodic tremor and slip) signals of volcanic and lower crust seismology. Type (II) is eventually linked to embedded rocks scratching along in situ crests, or to fissure opening at surface. A comprehensive field campaign was conducted from spring to summer 2010 to observe how these fractures relate to slope movement, fissure development and hydro-meteorological changes. Geophysical, hydrological, geodetic, and geotechnical monitoring was performed, complemented by daily soil sampling and UAV-based (unmanned aerial vehicle) photogrammetric data acquisition. First processing results help to evaluate on different theories of fracture generation.