A magnitude 8.5 earthquake struck off the east coast of Japan on Saturday, shaking buildings in Tokyo, but there was no danger of a tsunami and no reports of damage since the quake was extremely deep.
There were no reports of further irregularities at the Fukushima Dai-ichi nuclear plant, damaged four years ago in a massive 9.0 magnitude quake, or any other nuclear facilities.
The Shinkansen high speed train line had briefly stopped between Tokyo and Osaka due a power outage and some trains in Tokyo stopped as well for safety checks, causing crowds of commuters in some of the city's liveliest areas to mill around outside stations.
The quake, centered off the Ogasawara islands south of Tokyo, occurred at a depth of 590 km (370 miles) and, unusually, was felt throughout much of Japan.
"It shook violently. Our Buddhist altar swayed sideways wildly," Michiko Orita, a resident of the island of Hahajima, near the epicenter, told NHK national television. "I have not experienced anything like that, so it was so scary."