Many people probably feel that “Okinawa doesn’t get earthquakes.” It’s true that people here feel shaking less often than on Japan’s mainland — but it’s a mistake to assume tsunami risk is just as small. Okinawa’s own history shows otherwise.

What actually happened in 1771 — The Great Meiwa Tsunami

According to records from the Ishigakijima Local Meteorological Office, at around 8:00 a.m. on April 24, 1771, a magnitude 7.4 earthquake struck the sea near Ishigaki Island. What stands out is that the shaking itself caused no damage.

But a great tsunami then struck the Yaeyama and Miyako island groups. The dead and missing numbered 9,313 in the Yaeyama region and 2,548 in the Miyako Islands region, 11,861 in total. On Ishigaki Island, 48.6% of the population died — one of the deadliest tsunami disasters in Japan’s recorded history.

This tsunami carried massive coral limestone boulders, estimated at 500–600 tons or more, from the sea onto land. Known as “tsunami boulders,” some remain on Ishigaki Island and elsewhere today. That is the kind of force a tsunami carries.

There are two lessons to take from this.

  1. A tsunami large enough to kill roughly 10,000 people has actually happened in Okinawa.
  2. A major tsunami can occur even when the shaking itself was weak — which is exactly what happened with the Great Meiwa Tsunami.

Check the “elevation” of your home and workplace today

Preparing for a tsunami starts with knowledge, before any supplies. Specifically, it means knowing two things about the places where you spend your daily life.

1. Know your elevation above sea level

In some coastal areas of Okinawa, elevation signs are installed on utility poles and public facilities. Look for one near your commute route or your home. You can also check elevation on the Geospatial Information Authority of Japan’s map website.

2. Check the tsunami inundation assumption

Under the Act on Promotion of Tsunami-Resilient Community Development, Okinawa Prefecture has published a tsunami inundation assumption (published March 2015). It shows, by municipality, the expected inundation area and water depth if the largest- class tsunami were to occur under adverse conditions.

But the prefecture itself attaches an important caveat:

This does not mean a larger tsunami cannot occur.

Even areas predicted not to flood may, in reality, still flood.

In other words, the inundation map is not a guarantee that says “up to here is safe” — it is a tool for knowing “at least this much is dangerous.” Don’t read it backwards.

Alongside this, also check your municipality’s hazard map and its designated emergency evacuation sites (including tsunami evacuation buildings). You can reach these from your municipality’s disaster-prevention page, or from the evacuation information section of the Emergency Links page.

What to do when the ground shakes — JMA’s principles

Judging when to evacuate is not this site’s role. Here, we simply present the principles published by the Japan Meteorological Agency (JMA) and the Okinawa Meteorological Observatory, as they state them.

From JMA’s “To Protect Yourself from Tsunamis”:

  • If you feel strong shaking, move away from the coast and evacuate to higher, safer ground
  • If you feel weak but long, slow shaking, evacuate immediately just the same (as with the Great Meiwa Tsunami, a major tsunami can follow an earthquake that causes no shaking damage)
  • There isn’t time to wait and see the tsunami before fleeing
  • Tsunamis strike repeatedly. A later wave can be higher than the first
  • A tsunami doesn’t always begin by the sea receding. The tide not going out does not mean you’re safe

From the Okinawa Meteorological Observatory’s “What to Know About Major Earthquakes and Tsunamis”:

  • If you feel strong shaking or receive a tsunami warning, move away from the shore immediately and hurry to a safe place
  • Don’t assume “this spot is safe” — head for higher, safer ground
  • Even under a tsunami advisory, do not go swimming or shore fishing
  • Don’t let your guard down until the warning or advisory is lifted

Pitfalls specific to Okinawa

  • You may not notice shaking while at the beach, fishing, or doing marine leisure activities. You may not feel the shaking while in the water or right at the water’s edge. Pay attention to the people around you and to disaster radio or smartphone emergency alerts, and get out of the water the moment anything feels off.
  • Traffic jams, because this is a car-dependent society. If everyone along the coast tries to flee by car at once, the roads stop moving. Knowing, in advance, a high place or tsunami evacuation building you can reach on foot matters most precisely because life here assumes a car.
  • Visitors don’t know the area. When family or friends come to visit Okinawa, even just telling them “if it shakes, head for high ground” is worth doing.

What this article does not cover

This site does not cover whether an earthquake or tsunami is currently occurring, or active tsunami warnings and advisories. Always check JMA and other official up-to-date information. Follow JMA’s warnings and the evacuation information issued by your municipality when deciding whether to evacuate.