A Tsunami Risk “close to 100%”: Which Regions of France are Most at Risk?

After an earthquake off the coast of Kamchatka, several tsunamis hit different coasts of the Pacific Ocean. Metropolitan France could one day be affected.

“We are never sure of anything” when it comes to tsunamis, recalls Johnny Douvinet, professor of geography at the University of Avignon. For several years, this academic has been working on alerting populations, including tsunamis.

If the Pacific and Indian Ocean are frequently affected by tsunamis, like this Wednesday 30th July 2025 after an earthquake off the coast of Kamchatka, France could, even should, one day face such a phenomenon.

A risk close to 100% in the Mediterranean

During the United Nations Ocean Conference in Lisbon in 2022, UNESCO warned of the risk of a tsunami in the Mediterranean in the next 30 years.

Statistics show that the probability of a tsunami wave of more than 1 meter in the Mediterranean in the next 30 years is close to 100%.
Unesco

The Atlantic and the English Channel could also be affected.

According to the Ministry of Ecological Transition, “the most exposed coastlines concern: the Côte d’Azur (from Cannes to Nice), La Ciotat in Toulon, the Côte des Maures, the Perpignan coast, part of the northwest coast of Corsica (from Calvi to Galéria)”.

Up to 850,000 people to be evacuated

Johnny Douvinet explains that in the Mediterranean, two scenarios are feared.

“The first is a major earthquake in the Ligurian Sea (Italy)”, begins the professor. In this case, “one significant wave could affect Nice in ten minutes. And Marseille in 1 hour. ”

The second scenario is that of an earthquake in a northern Algerian fault. There, the entire Mediterranean rim could be affected in 1 hour 20 minutes, 1 hour 40 minutes, specifies the academic.

In the middle of the summer period, this represents 800 to 850,000 people to be evacuated.
Johnny Douvinet – Professor of geography at the University of Avignon

Damage, even without a 10 m wave

And, if everything depends on the intensity of the earthquake, the authorities are considering one wave of up to 1m50.2m ”, according to Johnny Douvinet. It is therefore not a 10 m high wave that would hit the Mediterranean coast. But when it comes to tsunamis, height isn’t everything.

“A one meter wave can cause significant material damage”, insists the professor. “A number of docks can be submerged, boats in ports can be swept away. ”

The Japan Rescue Association, whose country is accustomed to tsunami risk, explains the possible consequences depending on the size of the tsunamis:

0 to 30 cm: an adult can stand, but cannot walk;
30 to 50 cm: cars start to float, an adult can stand, hanging on;
50 to 70 cm: the water becomes powerful, even an adult can be carried away.
70 cm to 1 m: impossible to stay still. The probability of death in the event of a collision with a large floating object is close to 100%.

Watch out for speed

“More than the height, it is the speed of arrival of the waves” which is important, assures Johnny Douvinet.

It is also “the wave train ” which is important. Here, understand the sequence of waves. Because a tsunami is not just a wave, it is a sequence.

As a reminder, “78% of tsunamis are due to seismic activity, 10% to volcanic activity and landslides, and 2% to meteorological activity”, explains UNESCO.

A tsunami is made up of several waves which will generally flood the coastline every 10 to 30 minutes, sometimes for several hours. The first wave is often not the most important.
National Tsunami Warning Center (CENALT)

Populations ready?

Hence the importance of knowing “the signals before a tsunami ”, explains Johnny Douvinet. “A rapid fall in sea level or rapid retreat from the sea are natural warning signs of the imminent arrival of tsunami waves”, writes CENALT.

The other question is whether the populations and the authorities are ready, “because the preparation and awareness phase saves lives”, notes the academic.

“The authorities are aware of the risk, and it is a priority we can prepare without knowing the date”, recalls Johnny Douvinet. On the 19th January 2024, an FR-Alert notification had been sent to smartphones residents of nine departments in the South-East to warn them of the risk of a tsunami. It was obviously an exercise: a way of doing prevention.