The epicentres of past earthquakes (extract from the Sisfrance database) and location of the epicentral zone of the 11/11/2019 earthquake over a geological background map to the scale of 1:1 000 000 (Chantraine et al., 2006).
At 11:52 on 11 November 2019, the Ardèche and Drôme départements experienced a violent earth tremor. The magnitude of this earthquake, estimated at about 5 on the Richter scale, was quite exceptional given the low seismicity of this zone in the past.
The BRGM and INSU (CNRS National Institute of the Sciences of the Universe) have issued a synthesis of knowledge on this earthquake, based on observations by French experts in seismology and seismo-tectonics (INSU CNRS, IRSN, CEA, BRGM, Universities, CEREMA). The earthquake was comprehensively recorded and very quickly investigated thanks to the RESIF research infrastructure (French seismological and geodetic network) and seismological stations recently installed in the region, and real-time access to their data.
Ongoing field missions
Different organisations have sent teams into the field to study the earthquake and install additional seismometers in the zone affected, to better record the aftershocks and analyse site effects as well as the responses of certain constructions.
A task force from the AFPS (French paraseismic engineering association) is currently engaged in a diagnosis of damaged constructions. A post-earthquake macroseismic task force, piloted by BSCF-RéNaSS, will be conducting a mission from 18 to 22 November. This should produce a more accurate estimation of the earthquake's intensity at the epicentre and more distant zones.
Research work is also underway to link up all the different observations and produce a more comprehensive explanatory framework.
This earthquake should trigger a new debate on the characteristics and occurrence of intraplate earthquakes and the criteria for characterising active faults, in France in particular. It should also encourage the scientific community to intensify its efforts to better understand the geometry, history and recent activity of the fault system in south-eastern France.
Such efforts, which would combine seismic and geological approaches, would be perfectly in line with the aims of the "Alps and peripheral basins" project undertaken for the French Geological Reference Platform (RGF), which covers this earthquake zone, and would open up an opportunity for further research.
Furthermore, as regards the damage caused by this earthquake, its occurrence in the French context should provide material for comparing results with a view to refining the damage assessment models used in France for purposes of crisis preparedness.