A test conducted by the geothermal company Fonroche, in order to establish a possible link between the activity of its site near Strasbourg and earthquakes in November 2019 in the Alsatian capital, has been suspended after two new slight tremors, announced on Wednesday. October 28 the prefecture of Bas-Rhin.
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These two “seismic events” of limited intensity took place around the Fonroche geothermal site in Reichstett and Vendenheim (Bas-Rhin), north of Strasbourg: one Tuesday at 11:30 pm (magnitude 2.1), the other Wednesday at 5:39 am (magnitude 2.6), according to a press release from the prefecture.
This specifies that these tremors occurred during tests conducted by Fonroche on the Alsatian site.
Work has been suspended there since a first series of earthquakes that occurred in November 2019: on November 12, an earthquake of magnitude 3.9 had shaken the region of Strasbourg without causing damage or casualties.
In the days that followed, four very light earthquakes were also recorded.
Seismologists and researchers then judged "possible" that they were caused by geothermal activities carried out by Fonroche on the Vendenheim-Reichstett site, which the company then vigorously contested.
"These tremors are bad news"
At the end of September, the prefecture had asked the company to conduct additional investigations and Fonroche has been preparing since the beginning of October "an interference test and a tracing test", the latter requiring in particular the injection of water into the sub. -ground.
The last two earthquakes are linked to this tracing test, the company told the regional daily Les Latest Nouvelles d'Alsace (DNA) on Wednesday.
“Obviously, we are not happy to generate this seismicity and these tremors are bad news,” the general manager of Fonroche Géothermie Jean-Philippe Soulé told the newspaper.
"But it's full of information," he added.
On the other hand, for the earthquakes that occurred in November 2019, "we still have no conclusion" and "we are trying to understand if there is a link between the two," he said.
