Microseismic and meteorological monitoring of Séchilienne (French Alps) rock slope destabilisation

Rockfalls and deep-seated gravitational slope deformations are recognized as a major natural hazard across the mountainous regions with strong economical and social impacts on regional land settlement and transportation policies. In recent years these geohazards are increasing as a result of climate change and rapid expansions of human habitats and critical infrastructure. Unfortunately, the physical mechanisms and trigger of slope destabilization are rather complex and strongly site variable and thus, difficult to predict. As a result, some of the current researches aim to design efficient monitoring techniques able to detect changes in the slope conditions in order to anticipate catastrophic failures. Microseismic, meteorological and geodetic monitoring approaches are tested in this context. Here, we present ongoing investigations on the microseismic and the meteorological monitoring approach for Séchilienne case study (south-east of Grenoble city), being the most instrumented French hazardous slope for more than 20 years. The Séchilienne slope is characterised by a deep progressive deformation controlled by the network of faults and fractures and induced by rainfall (Vallet et al. 2015b). A particularity of this landslide is the absence of a well-defined basal sliding surface (Leroux et al, 2011). Two microseismic networks have been installed. A permanent seismic network, installed in May 2007 (Helmstetter and Garambois, 2010) by the the Multidisciplinary Observatory of Versant Instabilities (OMIV), to supplement the geodetic and geotechnical monitoring system operated since 1985 by the French “Centre d’études et d’expertise sur les risques, l’environnement, la mobilité et l’aménagement” (CEREMA) (Durville et al., 2009). Later in November 2009, a temporary microseismic network was set up by the National French Institute for risks and environment (INERIS). It consists of experimental in-depth probes and it is only one of the components of the INERIS experimental multi-parameter system, placed along the West border of the very active zone of the landslide (Dunner et al., 2010)