Paleoseismological investigations of the La Rouvière fault, unexpected source of the 11-11-2019, Mw 4.9 Le Teil surface rupturing earthquake (Cévennes fault system, France)

摘要: The Alpine region is one of the most seismically active areas in France (Drouet et al., 2020). If the actual horizontal velocity deduced from GPS is very low in the western Alps (Nocquet et al., 2016), the exhumation of about 2 mm/yr in the study area points out the active tectonic context (Sternai et al., 2019). For example, the Belledonne Massif is today affected by recurrent active but deep deformation, demonstrated by historical seismicity (Wilhelm et al., 2016), instrumental data (Thouvenot et al., 2003) and geodetic data (Walpersdorf et al., 2015). However, as elsewhere in the Alps, most of the seismicity is a background seismic activity highlighted by local and recurrent swarms. Compared to others swarms in the French Alps, the Maurienne unprecedented swarm (Gueguen et al., 2021) is similar to Vallorcine swarm (Cara et al., 2017) and to the Ubaye swarm (De Barros et al., 2019) in terms of tectonic and geological position: somehow linked with the reactivated Hercynian and/or Alpine structures and triggered in the crystalline basement. In parallel, in terms of tectonic geomorphology in the the Alps, kilometers scale recent scarps with normal motion are linked with gravitational movement and identified as gravitational sackungs (Hippolyte et al., 2006, Le Roux et al., 2009). They must be triggered by a debuttressing process controlled by glacial retreat and gravity but are distinct from “real” active tectonic features. Anyhow, in order to discuss the tectonic activity, the slip rates have to be quantified and few dating studies have been carried out to estimate those in the northern Alps yet. In both cases of geomorphic evidences or seismic evidences of …