With nearly 30,000 people dead or missing, the giant tsunami triggered by the Great East Japan Earthquake is the worst in the nation's history.
The death toll from the series of tsunami on March 11 is set to exceed the 22,000 lives lost in the 1896 Meiji Sanriku Tsunami, which also struck Honshu island's northeastern Pacific coast.
The first devastating waves of the March 11 tsunami exceeded 3 meters in height. They slammed into the coast about 30 minutes after the quake, according to the Japan Meteorological Agency.
In the Meiji Sanriku Tsunami, the first waves hit the shore just 20 minutes after the earthquake. With waves reaching a terrifying 38.2 meters, it demolished towns and villages deep inland across the V-shaped terrain of the Sanriku region.
Decades later, the same area was pummeled by the 1933 Showa Sanriku Tsunami, which towered at 28.7 meters and claimed 3,064 lives.
In 1993, a 31.7-meter tsunami triggered by a magnitude-7.8 earthquake in the sea southwest of Hokkaido devastated Okushiri island and left 230 people dead.
Records collected at a seawater level monitoring station in the port of Ofunato, Iwate Prefecture, provide a picture of how the nation's most devastating tsunami developed.
After the quake struck at 2:46 p.m. on March 11, the sea started receding. The water level began rising at 3:10 p.m., increasing to more than 3 meters by 3:15 p.m. Just three minutes later, the surge had swelled into a wall of water 8 meters high.
The meteorological agency's monitoring device was damaged by the increased water pressure, and ceased recording the sea level at 3:19 p.m. As a result, the agency was only able to announce that the tsunami was 8 meters or higher. However, an official said the waves were "likely to have been much higher."
As of Thursday, the highest level was recorded at the coast of Miyako, Iwate Prefecture, at 8.5 meters or more.
In that city, about 70 kilometers north of Ofunato, waves above 3 meters hit about 35 minutes after the quake, and reached a maximum 8.5 meters before records went blank.
Officials said the waves pounded a wide area along Pacific coastal regions about 30 minutes after the quake.
The wave measurements were taken at the shoreline, but the water continued to gush inland for several kilometers at great force.
According the Port and Airport Research Institute based in Yokosuka, Kanagawa Prefecture, eyewitnesses spoke of waves 11 meters higher than sea level crashing into a cliff.
Shigeo Takahashi, director of the Asia-Pacific Center for Coastal Disaster Research at the Port and Airport Research Institute, said that a wide area along the coast from Iwate to Fukushima prefectures was likely struck by waves higher than 10 meters.
"The size of this tsunami was probably unprecedented, and likely 1.5 times the scale of the Meiji Sanriku Tsunami," Takahashi said.
(This article was written by Yusuke Nikaido and Yasushi Okubo.)
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