A 6.8 magnitude earthquake has struck off Japan's north-eastern coast, triggering a tsunami warning which was later lifted.
There were no immediate reports of damage or injuries in the area, which was devastated earlier this year by a massive quake and tsunami.
The quake was centred about 185 miles north-east of Tokyo and at a depth of 12 miles, slightly south of where the 9.0 magnitude quake struck on March 11, said Japan's Meteorological Agency.
The agency issued a tsunami advisory, predicting waves of 20 inches along the coast of Miyagi and Fukushima prefectures, where a nuclear plant crippled by March's quake-spawned tsunami is located. The agency lifted the advisory about 30 minutes later.
There were no abnormalities in key equipment at the Fukushima Dai-ichi nuclear power plant, said Chie Hosoda, an official with Tokyo Electric Power, the plant's operator. She said some of the plant's workers assigned to the coastal side of the facility temporarily retreated inside the building.
This was the first sizeable quake in the area in over a month. In the weeks following the huge March quake, Japan was frequently rocked by aftershocks, including several stronger than magnitude 7.0. Their frequency and size have declined considerably.
In Onagawa, about 210 miles north of Tokyo, town official Hironori Suzuki said there were no immediate reports of damage or injuries. There was no visible swelling of the ocean, he said.
The quake caused buildings in Tokyo to sway. Bullet trains and several other local train services in the region were temporarily suspended for safety checks.
Just over 20,000 people died or disappeared across Japan's north-eastern coastline after the March earthquake and tsunami. Some 100,000 others were forced to evacuate their homes because of the threat of radiation from the crippled Fukushima plant.
March's tsunami destroyed cooling systems at that plant, sending its reactors to core meltdowns that caused a massive amount of radiation to leak out of the complex. The radiation leaking has since dramatically declined.