A strong earthquake with a preliminary magnitude of 6.8 jolted northeastern Japan off Fukushima prefecture on Friday, although no damage has been reported.
The quake struck off the Pacific coast at a depth of 20km at 2.36pm local time. Japan's meteorological agency has lifted a tsunami advisory for the area after no waves were sighted.
The 50cm tsunami warning was issued for the coastal areas of Fukushima and Miyagi prefectures severely damaged by the massive quake and tsunami earlier this year, but was lifted about 35 minutes later, Reuters reports.
The Tokyo Electric Power Company said no abnormalities had been found at radiation monitoring posts at the crippled Fukushima Daiichi nuclear power plant and cooling operations at the damaged reactors were continuing.
On 11 March, the northeast coast was struck by a magnitude 9 quake - the strongest on record in Japan - and a massive tsunami that triggered the world's worst nuclear crisis in 25 years at the Fukushima Daiichi plant.
The disaster left about 20,400 dead or missing.