Did you feel that? Earthquake in the Vendée!

An earthquake with a magnitude of 4.3 on the Richter scale struck throughout the region of Pays de la Loire on Friday, June 21st, 2019. Around 06h50 UTC – 08h50 local time – a loud noise was followed by a 10-to-15 second tremor. The epicenter [47.172°N 0.597°W] was located some 3.4km deep west-north-west of Vihiers, a commune of Maine-et-Loire some 31km south of Angers. The quake was felt as far as the south-Vendée and Niort.

Needless to say social media shook quite instantly with people wondering what had happened or even excitedly posting the “freaky” occurrence. Some had never experienced or even felt a quake before and were as curious as shaken up about it. Fortunately, there are no reported injuries or property damage, but there are reports of aftershocks.

The last time an earthquake occurred was in February 2018 and the force was like Friday’s. Earthquakes happen more often; they are just not big enough for us to feel.

In case you didn’t know, the Vendée is not immune to earthquakes and here’s why: the coastal area of the region is located to the south of the intraplate Armorican area. a geologic massif (an old mountain range) that spanning Brittany, the western part of Normandy, and the Pays de la Loire. The name Armorican Massif comes from Armorica, a Gaul area between the Loire and the Seine rivers.

The fault system curves in the Vendée from a south-east/ north-west into an east-west direction toward south-Brittany and further westward along the boundary fault of the West European basin and the British Shelf. The region’s tectonic history dates to Variscan times, a geologic mountain-building event some 370 million to 290 million years ago.

Due to its frequent seismic activity, the area is monitored both onshore and offshore.

Seismic activity cannot be ruled out in many parts of France. In 2011 the government issued a Seismic Zone map showing the risk zones. As you can see from this map (still current – we searched high and low for an updated map but didn’t find one) – the Vendée is in Zone 3 – indicating a moderate risk of earthquakes.

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Fault lines in France (wikipedia)

Should it be cause for panic? Absolutely not! The purpose of this map has much more to do with risk prevention and protection (e.g. construction zones, location of bridges, pipeline transport) and to enforce building safety standards and construction materials.

And are you confused by the time and depth measurements of earthquakes? Don’t feel alone! Here’s what you need to know:

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Areas with earthquake risk in France (wikipedia)
  • UTC stands for Coordinated Universal Time and is the same as GMT (Greenwich Mean Time), however, it doesn’t take the summer time change into account. Friday’s earthquake took place at 06h50 UTC – which would normally mean 07h50 in our time zone – however, UTC doesn’t count “spring forward” 1 hour… which means locally the earth shook at 08h50.
  • We were lucky to know the actual depth of the earthquake at 3.4 km. Where computations are too unreliable, the world-wide average depth of earthquakes is used 10km (a reliable average depth at which the earth plates shift)
  • News reports tend to err on the side of sensation. A magnitude of 4.8 and 4.9 are being reported. Indeed some websites can't make up their mind, reporting differing magnitudes in one article! We checked several renowned earthquake monitoring services, which say M4.3

Report your experience!
Why should you? Actually, Internet users are an important source of information in the collection of data used to form a more detailed snapshot of earthquake-prone regions.  The DYFI (Did You Feel It?) citizen science webpage for instance, was developed to get more complete descriptions of any occurrence world-wide, the damage caused and perhaps most importantly the effects of an earthquake on the community. Data submitted by the ‘average Joe’ is even used to create maps and graphs in ‘real-time’ or instantly.  DYFI encourages people to share their experience through a short questionnaire (just tick the boxes) – even if your community was already represented by another user. The more info is received on an area, the more reliable local information becomes.

Even if you didn’t feel the earthquake, your report is super important to gauge the percentage of ‘felt’ vs ‘not-felt’ experiences, as well as to gauge of where that boundary exists.

Report your earthquake experience here !

  1. Click on the earthquake that you think you felt, and
  2. Then select the "Tell Us!" link.
  3. If you don't see the earthquake you think you felt listed, use the green "Report an Unknown Event" button

This is the information or data collected about Friday’s earthquake, so far:
https://earthquake.usgs.gov/earthquakes/eventpage/us6000443c/executive
Current seismogram displays France:
 https://renass.unistra.fr/

What to do in case of an earthquake?

Indoors?

  • DROP to the ground where you are. Research has shown that most injuries occur when people inside buildings attempt to move to a different location inside the building or try to leave.
  • Take cover under a sturdy table or other piece of furniture; if that's not an option, cover your face/ head with your arms and crouch in an inside corner of the building.
  • Stay inside until the shaking stops
  • Stay away from glass, windows, outside doors and walls, and anything that could fall
  • If you’re in bed, stay in bed. Protect your head with a pillow, but roll away from any light fixture that could fall
  • Be aware that the electricity may go out, there may be gas leaks, and sprinkler systems or fire alarms may activate. 

Outdoors?

  • Stay outdoors
  • Move away from buildings, streetlights, and utility wires. The greatest danger exists directly outside buildings, at exits and alongside exterior walls.

In a vehicle?

  • Stop as quickly as safety permits and stay in the vehicle.
  • Afterwards, proceed with caution: roads, bridges, or ramps may have been damaged so don’t use them

Trapped under debris?

  • Cover your mouth with a handkerchief or clothing.
  • Tap on a pipe or wall so rescuers can locate you. Use a whistle if one is available. Shout only as a last resort. Shouting can cause you to inhale dangerous amounts of dust.
What not to do in case of an earthquake?
  • Do not use a doorway except if you know it is a strongly supported, load-bearing doorway (inside doorways don’t qualify)
  • Do not exit a building during the shaking.
  • DO NOT use the elevators.
  • In a vehicle, avoid stopping near or under buildings, trees, overpasses, and utility wires.
  • If you are trapped under debris, do not light a match! And do not move or kick up dust.

Do you feel informed? Great! Next time the earth shakes, rattles and rolls under our feet you’ll know the what and the why. Just remember that the last major historical earthquake in the Vendée (M6) occurred on January 25th, 1799. And the average for a (small) earthquake to occur in the Vendee is about every 2 years.

Sources: Geodynamic Models: An Evaluation and Synthesis By R. W. Van Bemmelen, https://www.emsc-csem.org/, https://earthquake.usgs.gov/, https://renass.unistra.fr/, https://www.ready.gov/earthquakes

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