Abstract
The district court decided that Shika atomic power plant must be stopped to operate. The outline of the main reason of the decision is as follows: The simulated earthquake ground motions used in the earthquake resistant design of power plants, are based on the empirical formulas such as Kanai formula (1966) and Osaki spectrum formula (1978). A little stronger acceleration than the ground motion for the earthquake resistant design was observed at Onagawa atomic power plant of Tohoku electric power Co. Therefore, more acceleration of the earthquake than the assumed earthquake motion for the design possibly attack the Shika power plant as well as the Onagawa and the Shika would be collapsed. However, the judgment underestimates the safety margin of the power plant. Recently, a strong earthquake of M6.9 and 17km away from the site attacked the Shika power plant, however, completely no damage and this fact proved the safety margin of the plant against the earthquake is enough much.
