Nuclear regulators on tsunami trace, screening

Japan's nuclear regulators say a new finding that points to a previously unknown massive quake off Chiba Prefecture some 1,000 years ago will not affect their assessment of the safety of power plants for now.

Earlier this year, researchers of the National Institute of Advanced Industrial Science and Technology and others found a new trace of a tsunami on the coast of Kujukurihama, in the prefecture.

Researchers said the tsunami was likely caused by an earthquake with a magnitude of about 8.5 off the Boso Peninsula.

On Thursday, members of the Nuclear Regulation Authority discussed the impact of the finding.

They looked at how it will affect safety screenings of the Tokai Daini Plant and other nuclear power facilities in Ibaraki Prefecture, north of Chiba.

Stricter safety requirements for the facilities were introduced following the March 2011 nuclear accident in Fukushima that was triggered by a massive quake.

At the meeting, it was reported that current screening criteria are based on the possibility of an earthquake with a magnitude of about 8.7 striking the area.

It was also reported that the new regulations' assumed height of a possible tsunami triggered by such a quake is higher than the estimated height of the tsunami of 1000 years ago.

The regulators concluded that the new finding will not affect their screening of the nuclear facilities for now, and said they will continue to gather information.