© AFP/Sam YehPhoto illustration of a seismic chart. Japan issued a tsunami warning Wednesday after a major 7.2-magnitude quake struck 160 kilometres (100 miles) east off the main Honshu island at 0245 GMT, swaying buildings in the capital Tokyo.
The quake struck at 11:45 a.m. local time and was centered about 90 miles (150 kilometers) off the northeastern coast - about 270 miles (440 kilometers) northeast of Tokyo - at a depth of about 6.2 miles (10 kilometers), Japan's meteorological agency said.
A 24-inch (60-centimeter) tsunami reached the coastal town of Ofunato, in Iwate prefecture, with other towns reporting smaller waves reaching shore about 30 minutes after the quake.
"We have confirmed that small tsunami have come up on the shores, but we have no reports of damage at this point," said Shinobu Nagano, an emergency and disaster response official in Iwate. "We are still trying to determine the impact of the quake."
Some train lines in the area were temporarily stopped after the quake, but they were restarted shortly after noon. Tohoku Electric Power said there was no damage at its nuclear power facility in the region.
The Pacific Tsunami Warning Center in Hawaii said a Pacific-wide tsunami was not expected.
There was a 6.3 magnitude aftershock shortly after the main quake, the meteorological agency said.
The U.S. Geological Survey said the 7.2-magnitude quake struck 8.8 miles (14.1 kilometers) underground, some 104 miles (168 kilometers) east of the closest major city of Sendai. The two agencies often have slightly different numbers.
Japan lies on the "Ring of Fire" - an arc of earthquake and volcanic zones that stretches around the Pacific Rim and where about 90 percent of the world's quakes occur.
In 1933, about 3,000 people were killed around Ofunato by an earthquake and tsunami that had a maximum wave height of 94 feet (28.7 meters), according to the USGS. In 1896, a magnitude 8.5 earthquake generated a tsunami that killed 27,000 people in the area.
Associated Press writers Eric Talmadge, Tomoko A. Hosaka and Jay Alabaster contributed to this report.
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"The United States Geological Survey plans to simulate and study small earthquakes in the desert this week using explosives and seismographs.
For the Salton Seismic Imaging Project, officials will bury 3,000 seismographs around the Coachella and Imperial valleys and measure the impact of the explosions, which will simulate 1.5- to 2-magnitude earthquakes."