A magnitude 7.4 earthquake hit 215 miles (345 kilometers) northeast of Tokyo, the U.S. Geological Survey reported on its website.
The quake was measured at a depth of about 25 miles and struck about 11:32 p.m. local time. Japan issued a tsunami alert for a possible two-meter wave.
A quake and tsunami disaster occurred in the nation on March 11, killing or leaving missing more than 27,000 people.