Kids Web Japan

The best way to reduce casualties is to let people know beforehand that a tsunami is coming. Based on this thinking, a group of tsunami experts began to attempt forecasting tsunamis. This was in 1952.

Tsunami forecasts are obtained by looking at where an earthquake occurred (the epicenter) and the strength of the earthquake (the magnitude). All the calculations were done manually at the time, so it took as long as 17 minutes to come up with a forecast.

A computerized communications system was introduced in 1980, reducing the forecast time to 14 minutes. But the tsunami that resulted from the Nihonkai-Chubu Earthquake of 1983 arrived before the forecast, killing 100 people. The forecast system was then improved so that the epicenter and magnitude could be determined automatically, and the time was halved to 7 minutes.

Immediately after this, though, the Hokkaido-Nansei-Oki Earthquake struck, followed by a tsunami, in 1993. The disaster took the lives of more than 200 people. This time the forecast was made in 5 minutes, but the tsunami - which reached a maximum height of 10 m - arrived in some places as soon as 3 minutes after the quake.