An extremely powerful earthquake rocked the Pacific Ocean floor Saturday, about 900 kilometers south of Tokyo.
Scientists said there is no danger of a tsunami because the quake was centered 600 or more kilometers below the surface.
The U.S. Geological Survey measured the earthquake at magnitude 7.8 - roughly as powerful as the earthquake that devastated Nepal last month and killed nearly 9,000 people.
The risk to populated areas posed by Saturday's seismic event is far lower, although it was felt in Tokyo, where buildings swayed about 8:25 p.m., local time. A dozen people suffered minor injuries.
Tokyo Electric Power Co said there were no abnormalities at the crippled Fukushima nuclear power plant following the quake. The runways at Tokyo's Narita airport were operating normally, but the high-speed bullet train service between Tokyo and Osaka was halted due to a power outage, NHK said.
Japan's Meteorological Agency pegged the earthquake as an even stronger jolt of 8.5-magnitude.
The nearest inhabited areas were small islands from the Bonin or Ogasawara archipelago, scattered over a wide area of that north Pacific region.
Seismologists said the earthquake was interesting scientifically because it represented an unusually sharp movement by the Philippine Sea plate of the Earth's crust, which presses beneath the much large Eurasia and Pacific plates.
Some material for this report came from Reuters.