The earthquake had a preliminary magnitude of 7.3 and struck in the Pacific Ocean off the coast of Miyagi prefecture at 5:18 p.m. (0818 GMT), the Japan Meteorological Agency said. The epicenter was 10 kilometers (6.2 miles) beneath the seabed and 240 kilometers (150 miles) offshore.
The area was shaken by repeated, smaller aftershocks, the agency said.
After the quake, authorities issued a warning that a tsunami potentially as high as 2 meters (2.2 yards) could hit. Sirens whooped along the coast as people ran for higher ground.
Ishinomaki, a city in Miyagi, reported a tsunami 1 meter (1 yard) high and other towns reported smaller tsunamis.
About two hours after the quake struck,