New perspectives in studying active faults in metropolitan France: the “Active faults France” (FACT/ATS) research axis from the Resif-Epos consortium

Abstract

Mainland France is part of a plate interior with a strong structural heritage, undergoing a low rate of deformation, where destructive earthquakes can nevertheless occur. In this paper, we emphasize that the knowledge of active faults is still largely fragmentary, and that significant efforts are needed to generate robust data, in particular on the numerous faults, that still lack any study. This is the aim of the "Failles ACTives France" (FACT) axis launched in the framework of the Transverse Seismicity Action (ATS) of the Resif-Epos consortium. We present some recent investigations carried out along suspected active faults in mountainous areas, their forelands and remote lowlands, which implement new approaches and new tools, and allow characterizing their Quaternary activity.

Late Holocene initiation of a deep rock slope failure in an alpine valley revealed by 10Be surface exposure dating (Chamonix, France)

“…4a) extends from the southern end of the Vallorcine fault for approximately 15 km between the Col des Montets and the Chéserys area. It is an active fault with a dominant dextral strike-slip component compatible with a tectonic origin for the postglacial deformation as suggested by shifted glacial landforms (Ritz et al, 2021). The southern part of the Remuaz fault is oblique to the Arve valley.…”

“…The Vallorcine fault is the geological contact between the Aiguilles Rouges gneiss and the Vallorcine granite. It was presumably the seismic location of the Mw 5.3 earthquake that affected the area in 1905 (Cara et al, 2017) and the Vallorcine seismic swarm is running along the fault (Ritz et al, 2021).…”