An earthquake with a preliminary magnitude of 6.6 shook western Japan on Thursday, the Japan Meteorological Agency said, adding that a tsunami warning was not issued.
There were no immediate reports of injuries or major damage and no irregularities at nuclear plants, but media said roughly 40,000 households were without power.
The epicenter of the earthquake was in Tottori prefecture at a depth of 6 miles, the agency said. The quake occurred at 2:07 p.m. and was followed by a weaker aftershock about 30 minutes later.
Earthquakes are common in Japan, one of the world's most seismically active area. Japan accounts for about 20 percent of the world's earthquakes of magnitude 6 or greater.
On March 11, 2011, the northeast coast was struck by a magnitude-9 earthquake, the strongest quake in Japan on record, and a massive tsunami. Those events triggered the world's worst nuclear crisis since Chernobyl a quarter of a century earlier.
(Reporting by Chris Gallagher, Kentaro Hamada and Osamu Tsukimori)