Risk of tsunami in Japan Sea studied

Risk of tsunami in Japan Sea studied

Fukui and 14 other municipalities on the coast of the Sea of Japan could be hit by a tsunami about a minute after an earthquake occurs, according to an estimate by a government panel of experts.

The panel, chaired by Katsuyuki Abe, professor emeritus at the University of Tokyo, calculated the height and arrival time of tsunami following earthquakes in the Sea of Japan for 173 municipalities across 16 prefectures from Hokkaido to Nagasaki Prefecture, and announced the results Tuesday. It is the first government study of this kind.

Estimates indicate 82 municipalities or about 50 per cent of those studied could be hit by tsunami at least 30 centimeters high, which is sufficiently strong to sweep a person away, within 10 minutes after an earthquake.

The town of Setana, Hokkaido, could be hit by a tsunami 23.4 meters high, the largest estimated. The panel said tsunami more than 10 meters high could hit 30 municipalities in six prefectures-Aomori, Akita, Yamagata, Niigata, Ishikawa and Hokkaido.

The panel also announced estimates focusing on flatland areas, as heavy damage is anticipated in such locations because they tend to have high concentrations of residential and commercial districts. The maximum tsunami height would be 12.4 meters in the town of Okushiri, Hokkaido, while tsunami ranging from four meters to 12 meters in height could hit the eastern half of the coastline from Hokkaido to Fukui Prefecture and from three to four meters for the western half from Kyoto to Fukuoka prefectures.

The height of tsunami in the Sea of Japan that could affect 11 nuclear power plants were also calculated, including one under construction. The largest possible tsunami would be 5.8 meters high near Hokkaido Electric Power Co.'s Tomari nuclear power plant. The estimated heights are all lower than the figures predicted by respective power companies.

The panel simulated 253 earthquake patterns occurring in 60 faults in the Sea of Japan, and analysed subsequent tsunami after those earthquakes. The most powerful estimated earthquake was one with a magnitude of less than 8. The magnitude of potential earthquakes in the Sea of Japan would be smaller than the much larger quakes with magnitudes of 9 or higher that are forecast in the Pacific Ocean. However, high tsunami waves would arrive more quickly because faults in the Sea of Japan tend to be close to coastal areas and are at shallower locations, according to the panel.

"Tsunami would arrive faster than expected. If people feel strong jolts, they should evacuate immediately," Abe said at a press conference held at the Land, Infrastructure, Transport and Tourism Ministry on Tuesday. Based on the latest estimate by the panel, the 16 prefectures concerned will designate areas at risk of potential flooding from tsunami and report them to the central government.

Details about tsunami in the Sea of Japan have been unclear so far. A joint panel of the land ministry, the Cabinet Office and the Education, Culture, Sports, Science and Technology Ministry has therefore been analysing faults in the Sea of Japan since January last year.

Concerning the tsunami predictions, another Cabinet Office panel projected in 2012 that a tsunami of up to 34 meters could reach Kuroshio, Kochi Prefecture, in the event of a massive quake along the Nankai Trough off the Pacific Ocean. However, the figure assumed a tsunami would hit a cliff, which would tend to add to its height.

The government panel therefore announced estimates regarding flatland areas on Tuesday, which are more important from the point of view of disaster prevention.

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