On 11 November 2019, a magnitude 5 earthquake occurred near the village of Le Teil in the Rhône River Valley in southern France producing an unexpected surface rupture with ground displacement. For the first time in France, Résif members and Terradue had the opportunity to use all modern seismological, geodetical, and geological techniques available to study this historically unprecedented seismic event.
The data, published on 27 August 2020 in Communications Earth & Environment, reveals that the earthquake was caused by the reactivation of the ancient La Rouvière fault. The fault formed during an extensional tectonic period some 20-30 million years ago during the Oligocene epoch, and was no longer considered to be active. The results raise the possibility that other faults could be reactivated in France and Western Europe and produce surface displacements, whereas the risk of earthquakes with surface rupture was until now considered as highly improbable.
To better assess the probability of such events, several teams of scientists in France are performing palaeoseismological investigations looking for evidence of past earthquakes along such faults.
For more information
Jean-François Ritz, jean-francois.ritz[at]gm.univ-montp2.fr