A strong earthquake with a revised magnitude of 5.4 on the Richter scale struck northeastern Japan centering Fukushima Prefecture on Thursday, the Japan Meteorological Agency said.
There were no immediate reports of casualties and damage.
No tsunami warning was issued for the 7:05 p.m. (1005 GMT) quake.
There were additional problems with the facilities at the crippled Fukushima Daiichi nuclear power plant by the latest quake, according to plant operator Tokyo Electric Power Co. The plant is still leaking a small amount of radiation after it was damaged by a magnitude 9.0-quake and tsunami on March 11.
The focus of the tremor was 9 kilometers below the northern Pacific waters off Fukushima Prefecture, the weather agency said.
It initially estimated the quake’s magnitude at 5.6, but later revised it upward to 5.4. The quake registered upper 5 on the Japanese seismic intensity scale of 7 in Iwaki city in Fukushima, about 190 km north of Tokyo.
The weather agency defines an intensity of upper 5 as strong enough to make most dishes in a cupboard and most books on a bookshelf fall. The areas were already severely hit by the March 11 quake and tsunami, which left about 21,000 people dead or missing.