The tsunami unleashed by the Great East Japan Earthquake exceeded 21 meters at one point on the coast between the stricken Fukushima No. 1 nuclear power plant and the Fukushima No. 2 plant, according to a survey of physical evidence left by the deluge.
The tsunami unleashed by the Great East Japan Earthquake exceeded 21 meters at one point on the coast between the stricken Fukushima No. 1 nuclear power plant and the Fukushima No. 2 plant, according to a survey of physical evidence left by the deluge.
The research, conducted jointly by the University of Tokyo and the Fukushima prefectural government on Feb. 6 and 7, shows that, all along the coast of the 20-kilometer exclusion zone around the Fukushima No. 1 plant, the March 11, 2011, tsunami substantially exceeded the expectations of nuclear plant operator Tokyo Electric Power Co.
Every one of the researchers’ 28 survey points showed evidence of a wave higher than the 5.7 meters TEPCO planners said was the maximum possible at the Fukushima No. 1 plant. Heights ranged from around 7 meters.
The survey was the first to look at physical evidence left by the tsunami within the no-entry zone.
The highest wave recorded was in Tomioka town on the Shimokobama coast, about 8 km south of the Fukushima No. 1 plant and north of the Fukushima No. 2 nuclear power plant.
Damage to the first floor of a restaurant on a cliff at that location indicated a maximum height of 21.1 meters. Researchers believe the topography of the bay leading to the survey point was the cause of the higher tsunami there.
TEPCO had estimated the tsunami that hit the No. 1 nuclear power plant spanning the towns of Futaba and Okuma was 14 to 15 meters high. The tsunami in Shimokobama appears to have been much higher.
At a bathing beach in Futaba, the tsunami’s height was estimated at 16.5 meters, based on damage to the trunk of a pine tree. In a sewage disposal site in Okuma, marks on a roof put it at 12.2 meters.
The tsunami was 12.2 meters high at a water pumping station in the Haramachi district of Minami-Soma city, and physical traces on the third floor of a building in Namie town indicated a height of 15.5 meters.
The wave was judged to be 13.2 meters on the Kegaya coast in Tomioka town, based on damage to the second floor of a hotel, and 12.8 meters near the river mouth in Naraha, because of marks on a roof.
“We were able to measure the traces before they disappeared. We will now look at the data and analyze it in detail,” said Shinji Sato, a professor of coastal engineering at the University of Tokyo.
The survey was part of a wider project by a group of researchers, including members of the Japan Society of Civil Engineers. Similar surveys have already been conducted in Iwate and Miyagi prefectures.
“It is very important that tsunami surveys were conducted in all of the coastal areas hit by the March 11 disaster,” said Kenji Satake, a professor of seismology at the Earthquake Research Institute of the University of Tokyo. “Judging from the data, the height of tsunami was higher than 10 meters in most of the survey spots from Namie to Tomioka.”
Satake said the figures did not conflict greatly with those already given by TEPCO at the Fukushima No. 1 and No. 2 nuclear power plants, but were a reminder of the scale of the disaster that knocked out the two nuclear power plants.