The quake caused disruption in some offices in Sendai
A powerful earthquake with a magnitude of 7.2 has hit Japan's north-east coast, injuring at least 40 people.
A tsunami alert was issued by Japan's meteorological agency, but later lifted after two small waves a few centimetres high hit the coastline.
The quake's epicentre is thought to have been 20km (12.4 miles) below the ocean off Miyagi prefecture, striking at around 1146 (0246GMT).
It shook buildings in the capital Tokyo, some 300km (186 miles) away.
The casualties were largely caused by the collapse of the roof of a swimming pool in Sendai city, Miyagi prefecture.
Initial reports suggested at least 80 people had been wounded.
But state broadcaster NHK later said one person had been seriously hurt and 13 were slightly injured.
Correspondents say Japan is extremely well prepared for earthquakes, and a similar magnitude quake elsewhere in the world would have proved deadly.
"There was a tremendous boom... People were screaming and headed toward the exit. It shook a lot... A lot of people were crying," a young woman at the scene told NHK.
Bullet trains were suspended, three nuclear power station were shut down automatically for safety checks, and flights at Tokyo's Haneda airport were temporarily halted as a precaution.
Some 17,000 households were reported to have lost power.
Two tsunamis around 10cm high (four inches) hit the coast about 15 minutes after the quake but were not thought to have caused any damage.
There were also reports of a landslide in what is a mainly rural part of Japan.
"I was cycling to work and initially thought I had a loose front wheel," Sendai resident Philip Wood told the BBC. "So I stopped to check. Then I realised it was an earthquake since cars were shaking and electric pylons were swaying all around me," he said. Japan is one of the world's most earthquake-prone countries, situated on four tectonic plates.
Tokyo was hit by a magnitude 6.0 earthquake last month, which injured at least 18 people.
The country's deadliest quake in recent memory occurred in the city of Kobe in 1995, with a magnitude of 7.3, that killed more than 6,400 people.
Before then, a 1923 quake, known as the Great Kanto Earthquake, killed more than 100,000 people.