On the morning of 4 April 1771, an earthquake off the Yaeyamas sent a wave into these islands that killed roughly twelve thousand people — about a third of everyone alive here. Boulders the size of houses are still sitting inland where the water put them.
The earthquake struck early in the morning. The wave that followed struck the southern and eastern coasts of Ishigaki hardest and swept far inland across the flat southern plain.
The death toll across the Yaeyamas and Miyako is generally put at around twelve thousand. Ishigaki’s population is thought to have fallen by roughly half, and some villages ceased to exist. It is, by proportion of population killed, among the worst natural disasters in Japanese history.
Contemporary records claimed run-up heights of over eighty metres, and that figure circulated for two centuries. Modern geological work has revised it down substantially — the current scientific consensus puts the maximum run-up at around thirty metres, which is still catastrophic and still among the highest ever recorded in Japan.
Scattered across the island’s northern and eastern shores are the tsunami-ishi — coral boulders weighing hundreds of tonnes, carried inland by waves and left where the water dropped them.
The best known is the Tsunami Ufuishi, a coral block the size of a small house sitting in a field well back from the sea. Several of these boulders have been dated, and they record more than one event over the last several thousand years.
They are, in effect, a hazard map written in rock. Japanese tsunami research uses them, and they are the reason this island’s coastal geology is studied internationally.
The aftermath was compounded by the poll tax, which the administration continued to levy on a population that had lost a third of its people and most of its farmland to salt. Famine and malaria followed, and the Yaeyamas did not recover their pre-1771 population for well over a century.
If you visit only the turquoise bay and the sand lanes, you will leave with an impression of these islands as uncomplicatedly beautiful. They are also a place that was nearly emptied within living memory of its own oral tradition.
Early morning, and then the wave
About a third of the population
On survivors, on salted farmland
Population does not recover for over a century
Still among the highest recorded in Japan
Dated, studied, and left where they landed
Give the Yaeyama Museum forty minutes. It is the only place that tells this in a way a visitor can follow.
A tsunami generated by an earthquake off the Yaeyama islands on 4 April 1771, which killed around twelve thousand people across Yaeyama and Miyako — roughly a third of the population. Ishigaki’s population is thought to have halved. Modern geological work puts the maximum run-up at about thirty metres, revised down from historical claims of over eighty.
Coral boulders weighing hundreds of tonnes, carried inland by tsunami and left where the water dropped them. Several have been dated and record more than one event over thousands of years, which makes them a natural hazard record — the reason Ishigaki’s coastal geology is studied internationally.
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