The wall of water that engulfed the coastline of Sendai in northeastern Japan a week ago was 10 meters high, three times what local officials had anticipated, according to a tsunami researcher.
As such, it ranked among the world's most powerful tsunami to pummel coastal plains, said Fumihiko Imamura, a professor of tsunami engineering at Tohoku University, who studied the devastation triggered by the March 11 Great East Japan Earthquake.
But the 2004 tsunami that ravaged coastal areas of the Indian Ocean in late 2004, claiming more than 200,000 lives, was even higher. That tidal wave was triggered by a magnitude-9.1 earthquake off Sumatra, Indonesia.
Imamura said the Sendai tsunami left its imprint at the 10-meter mark on a building of an elementary school in the Arahama district of the city's Wakabayashi Ward, where people took refuge.
Hundreds of bodies were discovered in the district.
Miyagi Prefecture had created 5-meter high coastal levees and planted pine groves stretching from 50 meters to several hundred meters wide along the coastline of Sendai and nearby Natori as part of its anti-tsunami efforts.
The step was based on a prefectural government projection that tsunami of up to 3 meters high could hit the region.
The projection derived from tsunami unleashed by a Miyagi offshore earthquake in the past. A powerful earthquake strikes the region at 37-year intervals on average.
The local government warned that the likelihood of a magnitude-7.5 hitting the area in the coming three decades was 99 percent.
Imamura said almost the entire area along the Arahama district and Natori bore marks of tsunami 10 meters high.
A reinforced concrete building was destroyed at a port in Natori.
In the past, experts had said that reinforced concrete structures could withstand the force of tsunami.
According to Imamura, the Sanriku coast spanning from the northern coastline of Miyagi Prefecture to Aomori Prefecture to its north could have been hit by tsunami twice as high as the one that lashed Sendai because tsunami tend to be amplified in sawtooth coastlines.
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