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Nuclear Power Information
Measures against Potential Massive Earthquakes

  • Basic Seismic Design
  • Settings of Design Basis Earthquake Ground Motions and Plant Licensing Status
Conventional DBGEM
(reported to the
in March 2009)
Revised DGBEM
approved by NRA
Takahama 550gal 700gal
Ohi 700gal 856gal
Mihama 750gal 993gal

Regarding the setting of design basis earthquake ground motions, we presented plans to take into account the rupture of multiple fault segments, namely FO-A, FO-B, and Kumagawa, and setting the depth of the upper edge of the faults to 3 kilometers below ground level. Based on these plans, we explained that the design basis earthquake ground motion would be 700 gal*1 for Takahama Nuclear Power Station (NPS), 856 gal for Ohi NPS, and 993 gal for Mihama NPS.

Following a review, a license was issued on February 12, 2015 for Takahama, October 5, 2016 for Mihama, and May 24, 2017 for Ohi.

Gal: A unit of acceleration which represents the intensity of seismic acceleration of the foundation/building due to an earthquake
Investigation of the F-6 Fracture Zone in the Site of Ohi Nuclear Power Station
We excavated a trench within the site area to visually examine potential geological variations.

Trench surveys, in which trenches are dug to confirm the existence of geological displacements, and boring surveys were implemented in the Ohi NPS site to verify that the F-6 fracture zone is not an active fault.

An approx. 70m long, 50 wide and up to 40m deep trench was excavated and it was confirmed that the crush zone was not an active fault.