Atomic Power Tsuruga nuclear power plant Units 1 and 2 (Tsuruga, Fukui Prefecture), located just below the "fracture zone" called soft faults, active faults through the site, "Fault Urasoko" there is a risk of moving under the influence -. It was found that this has been pointed out by experts.
It has been found that just below Tsuruga nuclear power plant’s reactors, faults called "crush zones" could move under the influence of the Urasoko active fault. Crush zones were previously thought as having "no activity", and they were not taken into account in the nuclear plant’s earthquake safety design, but it was discovered that in the Great Eastern Japan Earthquake, this kind of fault had moved.
Fracture zone immediately beneath the primary Tsuruga could force pulling horizontally "normal fault" is and can do compression, "thrust" is a difference, or cause earthquakes, the possibility of movement or during an earthquake is low had been with.
The head of the Geographical Survey Institute’s Kanto regional survey department, Mr Hiroshi Une, who is also a member of the NISA’s working committee for the re-examination of Tsuruga power plant’s earthquake safety, says that although Japan’s normal faults are not supposed to move, since the 11 March earthquake the earth’s crust is subject to forces which are different from those observed in the past, and although there are crush zones all over Japan, the Tsuruga power plant is a case needing special attention because an active fault (the Urasoko fault, last activated 4000 years ago) is running inside the plant premises. Japco will announce its conclusions by the end of August. (The orange lines on the map are the active faults. The grey lines are the crush zones).
Hiroshi Une said: "the commonly held opinion that normal faults don’t move has collapsed".
Fast breeding reactor Monju is close to the Shiraki-Nyu active fault, and crush zones of the normal fault type were confirmed below the reactor.
However, the April 11, Fukushima Hamadori magnitude in the region (M) when an earthquake of 7.0 on the fault normal fault Idozawa (19 km long) is found to be moved. Tectonic geomorphology professor Mitsuhisa Watanabe of Toyo University says : "however robust a reactor is made, if the ground tilts, it will get broken. Keeping normal faults out of one’s thought was a mistake and that must be revised"
Urasoko is seen as the fault was active in about 4,000 years ago.
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