Japan was set on Thursday to lift a week-old warning that a "megaquake" potentially causing colossal damage and loss of life could strike, the government said. The alert that such a catastrophe might hit the archipelago of 125 million people prompted thousands of Japanese to cancel holidays and stock up on essentials, emptying shelves in some stores. Japan's disaster management minister Yoshifumi Matsumura said the "special call for attention" would be lifted at 5:00 pm (0800 GMT) assuming there was no major seismic activity.
Matsumura cautioned, however, that the "possibility of a major earthquake has not been eliminated", urging people to regularly check their preparedness "for the major earthquake that is expected". Last Thursday, Japan's weather agency said the likelihood of a megaquake was "higher than normal" after a magnitude 7.1 jolt earlier in the day that injured 15 people.
That was a particular kind of tremor known as a subduction megathrust quake, which in the past has occurred in pairs and can unleash massive tsunamis. The advisory concerned the Nankai Trough between two tectonic plates in the Pacific Ocean. The 800-kilometre (500-mile) undersea gully runs parallel to Japan's Pacific coast, including off the Tokyo region, the world's biggest urban area and home to around 40 million people.
In 1707, all segments of the Nankai Trough ruptured at once, unleashing an earthquake that remains the nation's second-most powerful on record. That quake -- which also trigger.