Can we fear new earthquakes in the Vannes region? If so, could they gain in intensity?
Julie Perrot, lecturer specializing in seismology at IUEM (European University Institute of the Sea), Plouzané (29): “Earthquakes, there will be others. It’s sure and certain. Stronger, I don’t know. We are not in a region where the faults are of great amplitude, have great lengths. We are also not in a region where the constraints, the speeds of the plates are such that we can have big earthquakes. I can’t tell you that there won’t be any stronger than magnitude 3.1
. There was one at Hennebont of magnitude 4.3 in 2002. But it should not exceed magnitude 6.”
“When there is an earthquake, even a very small earthquake, there is a change in the forces around it. This is normal since there is a portion of fault which will vary from a few meters to a few tens or even hundreds of km (but we are not in this case in Brittany). This will change the balance of power all around the region, what we call constraints. This could possibly influence other faults located in the region.
Usually, we have the opposite pattern: we have a big earthquake then lots of small earthquakes. These are called aftershocks. It’s classic.”
The last earthquake was only of magnitude 3.1, yet it was really felt by the residents. How is this explained?
“The earthquake must have been superficial, not very far from the surface, that’s why it was felt well.”