Tsunami was up to 21 metres in Fukushima

The tsunami that hit Fukushima Prefecture on March 11 was particularly high--possibly up to 21 metres--along the coast in the centre of the prefecture where the Fukushima No. 1 nuclear power plant is located, a survey has found.

The height of the tsunami was previously assumed to have been about 15 metres at the nuclear plant, but this could not be confirmed because the area within a 20-kilometre radius of the plant is designated a no-entry zone.

Researchers including Shinji Sato, a professor at the University of Tokyo, obtained permission from local governments to enter this zone, and for the first time since the tsunami, were able to survey coastal areas Monday and Tuesday.

They found that areas struck by higher tsunami were concentrated on the coast in the prefecture's centre. For example, at Tomioka, which is eight kilometres south of the nuclear plant, a tsunami height of 21.1 meters was observed.

The maximum height was 10 metres along much of the coast in the prefecture's south.

"It is necessary to do more research on what caused the tsunami to hit the central part of the prefecture particularly hard," Sato said.