An earthquake of magnitude 7.3 struck Saturday morning local time off Japan's east coast, near the crippled Fukushima nuclear site, the US Geological Survey said.
Japan's emergency agencies declared a tsunami warning for the area.
Japan's Meteorological Agency raised the tsunami warning for the area of Honshu. But the US Pacific Tsunami Warning Centre did not post warnings for the rest of the Pacific.
The quake hit at 2.10am Saturday Tokyo time (1710 GMT Friday), the USGS said.
The tremor was felt in Tokyo, some 300 miles away.
All but two of Japan's 50 reactors have been offline since the March 2011 magnitude-9.0 earthquake and ensuing tsunami triggered multiple meltdowns and massive radiation leaks at the Fukushima Dai-ichi nuclear power plant, about 160 miles north east of Tokyo.
About 19,000 people were killed as the result of that quake and its consequences.