A 6.0-magnitude earthquake hit off the coast of Fukushima in Japan on Friday but there was no risk of a tsunami, officials said.
The shallow quake hit at 04:59 pm (0759 GMT), 255 kilometres east of Ishinomaki, according to the United States Geological Survey.
The Japan Meteorological Agency said the quake posed no tsunami risk.
Later Friday another quake hit northeastern Japan, close to the disaster-hit Fukushima nuclear plant, but there was again no fear of a tsunami, Japanese and US authorities said.
The 5.4-magnitude quake struck at a depth of 47 kilometres in the Pacific Ocean, 28 kilometres east-northeast of Iwaki, USGS said.
There were no immediate reports of damage or injuries and no abnormalities were detected at nuclear power facilities in the region, including the Fukushima Daiichi nuclear plant, Japan's public broadcaster NHK said.
A 9.0-magnitude earthquake in March 2011 triggered a massive and deadly tsunami, which smashed into the Fukushima nuclear power station and sparked the world's worst atomic accident since Chernobyl in 1986.
Its operator is working to clean up and dismantle the reactors in a process that is expected to take at least four decades.