When two earthquakes of magnitude 6.5 and 7.3 struck Kumamoto Prefecture in April, the shock was felt not only in Kumamoto but also about 170 km away, in the small town of Ikata, Ehime Prefecture, home to a nuclear power plant.

For years, residents had been told that the Median Tectonic Line, which runs from Kyushu to Honshu and passes just 5 km away from the Ikata plant, was not active and that there was nothing to worry about. After the April quakes, no abnormal atomic activity was reported, but residents are now worried a large quake in the area, followed by tsunami, could not only damage the plant but also make evacuation from the peninsula Ikata lies on impossible.

The restart of Ikata reactor 3, slated for Aug. 12, has put those concerns in sharp focus and raised questions about just how realistic evacuation will be in the event of a natural disaster — especially an earthquake that sends a tsunami churning toward the nearly 124,000 residents living within 30 km of the plant.