Tsunamis in French Polynesia

When the ocean wakes up

French Polynesia, located in the heart of the South Pacific, is a paradise region but exposed to powerful natural phenomena, including tsunamis. These giant waves, often triggered by underwater earthquakes, can strike the ribs with devastating force. The July 30, 2025, a tsunami has once again reminded the inhabitants of the Marquesas of this reality. I offer you below a complete exploration of the phenomenon, of his origin has his impacts in Polynesia, passing through the historical events and preventative measures.

What is a tsunami?

Training mechanism:

• • • An earthquake occurs in a subduction zone, where one tectonic plate pushes under another.
    • This deformation of the seabed generates a ocean wave which spreads at high speed.
    • Approaching the coast, thewave slows down but gains height, which can reach several meters.

History of tsunamis in French Polynesia

French Polynesia has experienced several tsunamis since the 19th century, some of which have caused significant damage.

Key events:

On Marquesas Islands are particularly vulnerable due to their shallow coastal slope and lack of protective reefs.

The tsunami of July 30, 2025: a brutal reminder

On the night of July 29-30, 2025, a magnitude 8,8 earthquake hit the Kamchatka Peninsula, in eastern Russia. This earthquake, one of the most powerful recorded in the region since 1952, triggered a tsunami warning across the Pacific.

Impact in French Polynesia:

• • • Archipelago affected : The Marquesas, notably Nuku Hiva, Ua Huka and Hiva Oa
    • Wave height : Between 1,10 m and 2,50 m, with peaks of 1,5 m observed in Nuku Hiva
    • Reaction of the authorities : Rapid evacuation of 700 people to safe areas, activation of sirens and the FR-Alert system
    • Consequences : No major damage or casualties. The alert was lifted on July 30.

The High Commission welcomed the exemplary preparation of the inhabitants, reinforced by regular evacuation drills.

Prevention and surveillance in Polynesia

French Polynesia has an advanced surveillance system, piloted by the Polynesian Tsunami Prevention Center at the Geophysics Laboratory of Tahiti.

Means of prevention:

• • • Real-time seismological analysis
    • Numerical simulation to estimate wave heights and risk areas
    • Rapid dissemination of alerts via media, social networks and local sirens

Instructions in case of alert:

• • • Evacuate to higher ground or predetermined fallback zones
    • Turn off the electricity and gas
    • Protect animals and property
    • Do not return to the coastal area before the alert is officially lifted

Ultimately

The tsunami of July 30, 2025, although without human consequences, reminds us that the French Polynesia remains exposed to major natural risks. Thanks to a effective coordination between the authorities and the population, the impacts have been minimized. History shows that the tsunamis can strike at any time, and that the Preparation remains the best defense.