This Monday, December 9, shortly before noon, a magnitude 4 earthquake shook Ubaye and the Italian border, east of Saint-Paul-sur-Ubaye.
Philippe Guéguen, research director at the Institute of Earth Sciences (ISTerre) in Grenoble describes this earthquake as “usual”. “Compared to those in Japan, it’s not important at all. But in France, we have four or five earthquakes like that per year,” explains the director, who wants to be reassuring. Several people in Grenoble or Embrun felt the tremors; this is the case of Jocelyn Auffret, 52 years old. While he was teleworking in Embrun, avenue Charles-de-Gaulle, he felt his office move. “It sounded like a van engine being started. My screens shook and the desk, which was rather well fixed, moved a little,” explains the fifty-year-old who estimates the duration at five or six seconds.
“There has been a gradual increase in activity since the beginning of August”
Agnès Helmstetter, also a member of ISTerre, recalls that this area of Ubaye, particularly the Sérenne fault, is very active. “The largest earthquake in the area dates back to 1959 and reached a magnitude of 5.5. Others, less intense, have taken place since. As it is a very active area, it is well documented because it is well covered by measuring instruments. Last year, there was a magnitude 3 earthquake, for example. And this year, just from the 1is August, Sismalp detected 3,477 earthquakes in Ubaye of magnitude greater than or equal to 0, including 18 of magnitude greater than 2. There has been a gradual increase in activity since the beginning of August with a first peak on August 20, then another peak on October 27 (with a magnitude 3 earthquake). This Monday, about an hour before the magnitude 4 earthquake, there was a 2.3. »
France
