Tsunami as tall as nearly 30 meters could hit coastal areas of northern Japan if a mega earthquake occurs in a deep-sea area off Hokkaido or Iwate Prefecture along the Kuril Trench or the Japan Trench, a governmental panel of experts said Tuesday.
In the event of such a mega quake, government buildings, including city halls, of at least 32 cities, towns and villages in Hokkaido, Aomori and two other prefectures in northern regions would be inundated, with power stations and railways likely to be damaged as well.
The panel of experts at the Cabinet Office considered two scenarios in which mega quakes hit the region. One was an earthquake of magnitude 9.1 in an area along the Japan Trench, off the Sanriku and Hidaka coasts. The other was an earthquake of magnitude 9.3 in an area along the Kuril Trench, off the Tokachi and Nemuro coasts.
The panel estimated the maximum heights of tsunami that would hit Pacific coastal areas of Hokkaido, Aomori and five other prefectures down to Chiba, and the areas that could be inundated by tsunami. The panel found that the city of Miyako, Iwate Prefecture, could be hit by a tsunami as tall as 29.7 meters, and the town of Erimo, Hokkaido, could be hit by one of up to 27.9 meters.
Elsewhere, the Kushiro, Hokkaido, city hall could be inundated to a height of up to 5.9 meters just 34 minutes after the quake, while the Aomori city hall could be flooded to a height of up to 1.1 meters, according to the panel's calculations. Among prefectuctural government buildings, only that of Aomori Prefecture is foreseen to be inundated, to a height of up to 1.7 meters.
Details of the presumed extent of inundation and other damage in Iwate Prefecture were not made public, in line with the prefectural government's request on the grounds that it "may affect the post-quake reconstruction from the Great East Japan Earthquake."
In the hypocentral region considered this time, a mega quake is estimated to have occurred once every few hundred years. In light of the passage of time since a mega quake hit previously, in the 17th century, the panel warned, "The imminency of a mega earthquake is high." The Cabinet Office plans to compile casualty and economic damage projections within this fiscal year.
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