A strong earthquake with a preliminary magnitude of 7.1 shook northern Japan yesterday, but there were no immediate reports of damage or injuries.
The quake was centered about 480km under the seabed off the western coast of Japan's northernmost main island of Hokkaido, at a location about 1,300km northwest of Tokyo, the Meteorological Agency said. It struck at 3:26pm.
The agency said there was no danger of tsunami, powerful ocean waves caused by seismic activity. The quake was most strongly felt in Aomori and Iwate, the two farthest-north prefectures on Japan's main island of Honshu.
The agency said the latest quake was unrelated to Saturday's three major quakes that hit another northern prefecture, Miyagi, leaving at least 420 people injured and hundreds of homes damaged.
Yesterday's quake, also felt in that region, did not cause any further damage there.
People in northeastern Japan braced for more tremors yesterday but a meteorological official said they weren't linked to a deadly cyclical quake that hits the region.
A moderately strong aftershock with a magnitude of 4.3 on the Richter scale rattled the area around Kanancho in Miyagi prefecture, about 300km north of Tokyo, fraying the nerves of anxious residents still further.
Saturday's earthquakes injured more than 400 people and caused landslides and power blackouts in Miyagi, a mostly rural area with a population of around 2.33 million.
But there was no link with the so-called Miyagi-oki earthquake, which has hit the region cyclically about every 30 to 40 years and last struck in 1978, killing 28 people, a meteorological agency official said.
The first temblor on Saturday, measuring 5.5 on the Richter scale, hit shortly after midnight, followed by a second measuring 6.2 about seven hours later. Aftershocks rattled the area, including one on Saturday afternoon with a magnitude of 5.4.
Some 421 people were injured and 2,451 were evacuated, Miyagi police said. Few of the injuries were serious.
The quakes affected a wide swathe of mostly rural northeast Japan, destroying homes and cutting off power to some 130,000 households at one point.
Some houses still lack water, but other facilities have been largely restored and residents of rural Kanancho, close to the epicenter, have begun sifting through the wreckage of their homes.
Around 600 troops from Japan's Self Defense Forces have arrived to help.
An earthquake of magnitude 6 or higher can inflict widespread damage when centered in a heavily populated area.