A strong earthquake shook Tokyo and other areas of eastern Japan on Friday, but no tsunami warning was issued.
The magnitude 6.1 quake was centred off the east coast of Chiba Peninsula at a depth of 44.5 kilometres, the US Geological Survey said.
Strong shaking was reported in Chiba and Ibaraki prefectures, but the USGS said there was little chance of serious damage or fatalities.
Kyodo News service said no problems were reported at the Tokai No. 2 nuclear power plant in Ibaraki.
A strong earthquake hit central Japan on May 5, killing at least one person and injuring more than 20 others.
Japan is one of the world's most earthquake-prone nations. A massive 2011 quake in the country's northeast caused a devastating tsunami and nuclear plant meltdown.