YOKOHAMA--The historic coastal city of Kamakura in Kanagawa Prefecture faces the prospect of being wiped out by tsunami at some point.
YOKOHAMA--The historic coastal city of Kamakura in Kanagawa Prefecture faces the prospect of being wiped out by tsunami at some point.
The Kanagawa prefectural government has drastically revised its calculations of giant tidal waves crashing into the city, which sits on Sagami Bay, some 45 kilometers southwest of Tokyo.
It now assumes that tsunami as high as 14.4 meters could swamp the city, which is surrounded on three sides by forested hills.
Under the latest projections, the height of such a tsunami is nearly triple the previous assumption of about 5 meters, or almost the same as the one that devastated the northern Tohoku region on March 11 following the Great East Japan Earthquake.
The prefectural government said a catastrophic tsunami on the scale of one triggered by the Meio Earthquake in 1498 would likely be 12 meters high and inundate areas 2 kilometers inland. Historic landmarks such as the "Great Buddha" statue and the Tsurugaoka-Hachimangu shrine could be caught in its path.
The prefectural government said that the tsunami would also flood most municipalities facing Tokyo Bay.
Based on the new assumptions, coastal municipalities of Kanagawa Prefecture will notify residents of the dangers they may face by distributing what is known as a hazard map. They will also designate more buildings as sites to evacuate to in times of disaster.
The Tokyo metropolitan government also plans to re-evaluate its tsunami assumptions by spring 2012. The Chiba prefectural government has also begun to review coastal areas that could be devastated by tsunami.
The Kanagawa prefectural government's review is in line with the findings of an interim report issued by a research committee of the Central Disaster Management Council in June.
It looked at descriptions in ancient documents and studied the area's geological characters. The prefectural government identified several patterns pointing to the likelihood of a "largest-class" tsunami striking at some point.
It had previously assumed that tsunami of around 5 meters in height could strike Kamakura, based on the probability of a temblor occurring on the same scale as the 1923 Great Kanto Earthquake that leveled much of Tokyo and surrounding areas, claiming some 100,000 lives.
In the latest review, the prefectural government looked at the impact of the 1703 Genroku Earthquake, the 1605 Keicho Earthquake and the 1498 Meio Earthquake.
It is known that tsunami more than 5 meters high struck the Kanto region during the Genroku Earthquake.
The epicenters of the other two earthquakes are not known.
In its latest projection, the prefectural government came up with a worst-case scenario for the epicenters and concluded that Kanagawa Prefecture would suffer a major hit from tsunami.
According to its calculations, a temblor matching that of the Keicho Earthquake would produce a tsunami up to 14.4 meters high at high tide.
In the case of a temblor of the same scale as that of the Meio Earthquake, the height of tsunami would be 12 meters.
Under current thinking, giant tsunami could even reach central parts of Yokohama and Kawasaki cities, causing flooding in underground shopping arcades at Yokohama Station.
"There is no way to avert a largest-class tsunami," said Kanagawa Governor Yuji Kuroiwa.
The prefectural government has focused its attention not only on building breakwaters and other structures but also on steps to heighten awareness among residents to flee to higher ground before a tsunami hits.
(This article was written by Mitsuteru Mori and Hirotaka Yamaguchi.)