The Nuclear Regulatory Authority has broadened the definition of active geological faults that is used in the review of the safety of nuclear power plants. Until this point, faults that have shifted in the past 120,000 to 130,000 years have been regarded as active.

Now the NRA says that faults that have shifted at least once in the past 400,000 years should be labeled as active. This new definition will be incorporated into the NRA's new post-Fukushima safety standards, which are expected to go into force next July.

This change strengthens one of the main pillars of nuclear safety standards. Even under current standards it is prohibited to build reactors and other critical nuclear facilities on active fault lines. Given how quake-prone Japan is, the NRA's broadening of the definition of active faults is a welcome step in the right direction.