Earthquakes guide
Tsunami Warning Signs: What to Do When the Sea Pulls Back
A tsunami can reach the nearest coast within minutes of an earthquake, before any official warning. Knowing the natural warning signs, and moving straight away, is what saves lives.
Updated 4 November 2026
The natural warning signs
- Strong or long shaking. If you are on the coast and the ground shakes hard enough to make it hard to stand, or for longer than about 20 seconds, a tsunami may be on its way.
- The sea pulls back. The water may suddenly drain away from the beach, exposing the sea floor, reefs and stranded fish. The wave follows.
- A loud roar from the sea, like a train or a jet.
Any one of these is enough. Don't wait for an official warning, and don't go down to the shore to look.
What to do
- Go to high ground or inland straight away, on foot if you can: roads jam quickly. Aim for at least 30 metres above sea level, or 3 km inland. Follow tsunami evacuation signs where there are any.
- If you can't get out of the zone in time, go to the upper floors of a strong, reinforced-concrete building, the third floor or higher. This is called vertical evacuation.
- On a boat, head out to deep water, away from the coast, if there is time and it is safe. Tsunamis are small in the deep ocean.
- Stay away for hours. A tsunami is a series of waves that can keep arriving for eight hours or more, and the first is often not the largest. Return only when officials say it is safe.
How a tsunami travels
Most tsunamis are caused by large undersea earthquakes that suddenly lift or drop the sea floor; landslides and volcanic eruptions can cause them too. In the deep ocean the waves move at around 700 to 800 km/h, as fast as a jet, but may be less than a metre high. As they reach shallow water near the coast they slow down and pile up, sometimes into walls of water many metres high, or a fast-rising flood that pours far inland.
That speed is why the nearest coast may have only minutes, while a coast across the ocean has many hours. The 1960 Chile tsunami reached Japan about 22 hours later.
Official tsunami warnings
Tsunami warning centres watch seismometers and sea-level gauges, including deep-ocean pressure sensors, and issue messages within minutes of a large earthquake. The US National Tsunami Warning Center (Alaska) and Pacific Tsunami Warning Center (Hawaii) cover the US and much of the Pacific; Japan, Indonesia, Chile and the countries around the Indian Ocean and the Mediterranean have their own.
| US alert level | What it means |
|---|---|
| Warning | A dangerous tsunami with widespread flooding is expected or under way. Move to high ground or inland. |
| Advisory | Strong currents and dangerous waves are expected. Stay out of the water and away from beaches and harbours. |
| Watch | A distant earthquake may have caused a tsunami. Stay alert and be ready to act. |
| Information statement | An earthquake happened, but there is no threat or it is very far away. |
Quake shows the latest messages from the US tsunami warning centres. Official alerts in your country, by siren, phone alert, radio or TV, always come first.
Before you go to the coast
- Check whether your home, work or holiday spot is in a tsunami zone, and learn the route to high ground.
- Know the warning signs and agree a meeting point with your family.
- Read What to do in an earthquake: the advice for the shaking comes first.
Not an official warning service. In an emergency, follow your local authorities.