Fault under Japan's Oi nuclear plant may be active

Japan’s only working nuclear power plant sits on what may be a seismic fault in the earth’s crust, a geologist has warned, saying it is “very silly” to allow it to continue operating.

Mitsuhisa Watanabe says the earth’s plates could move underneath the Oi nuclear plant in western Japan, causing a catastrophe to rival last year’s atomic disaster at Fukushima — although some of his colleagues on a nuclear advisory panel disagree.

“It is an active fault. The plates shifted some 120,000 to 130,000 years ago for sure,” Watanabe, of Tokyo’s Toyo University, told AFP.

“In research that I have conducted on active faults in Japan and overseas, structures built above them were all damaged” when they moved and caused an earthquake, he said.

Watanabe, a tectonic geomorphologist, is part of a five-member team tasked by the Nuclear Regulation Authority with looking into the tectonic situation underneath the plant, where the country’s only working reactors are.

Geomorphology is the study of the evolution and configuration of landforms.

Under government guidelines atomic installations cannot be sited on a fault — the meeting place of two or more of the plates that make up the earth’s crust — if it is still classed as active, that is, one that is known to have moved within the last 130,000 years.

A positive finding would mean regulators must order the suspension of operations at the plant in Fukui prefecture.

But other scientists on the panel say it is too early to class it as an “active” fault that might pose a risk to the plant, calling for “a scientifically calm approach“.

The team’s head, Kunihiko Shimazaki, who is also a member of Japan’s nuclear regulatory body, says the geological scarring they can see was probably caused by little more than a long-ago landslide.

Instead of the definitive green light that plant operator Kansai Electric Power was hoping for, the committee last week said only that more work needs to be done.

“It’s desirable for all members to reach a conclusion by consensus,” Shimazaki said.

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