An earthquake with a preliminary magnitude of 6.2 hit off the coast of northeastern Japan on Sunday but no tsunami warning was issued, the Japan Meteorological Agency said.
The epicenter of the 7.23 p.m. (1023 GMT) earthquake was off the coast of Fukushima prefecture and measured at a depth of 50 km (30 miles), the agency said.
There were no were immediate reports of damage.
Earthquakes are common in Japan, one of the world's most seismically active areas. Japan accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.
Public broadcaster NHK TV says utility companies are checking on the nuclear reactors in the area.
In 2011, Fukushima was hit by a powerful quake, tsunami and nuclear meltdown, the worst nuclear disaster since Chernobyl.