A powerful earthquake struck about 100 miles northeast of Tokyo and about 30 miles southwest of the crippled Fukushima Daiichi nuclear plant on Monday.
Meanwhile, Japan has expanded the evacuation zone around the Fukushima plant because of high levels of accumulated radiation.
The Monday evening aftershock — reported as being between 6.6-magnitude and 7.1-magnitude — hit exactly a month after a 9-magnitude earthquake created a tsunami that killed an estimated 28,000 people.
The quake swayed buildings in Tokyo and triggered several landslides in the city of Iwaki, including one that buried three houses and trapped four people inside, but did not cause a tsunami, according to CNN.
Japan did, however, temporarily issue tsunami warnings for parts of the north-east coast. NHK, the public broadcaster, warned of tsunami up to 2 meters (over 6 feet) high on the coast of Ibaraki prefecture. The government's meteorological agency warned people in Ibaraki to evacuate to higher ground, according to the Guardian.
Meanwhile, representatives of Tokyo Electric Power Co. (TEPCO) announced that workers had finished dousing reactors at the damaged Fukushima nuclear plant with water, and would widen the 12-mile evacuation zone because of accumulated radiation.
Chief Cabinet Secretary Yukio Edano said villages and towns outside the 12-mile evacuation zone that have had more accumulated radiation would be evacuated, Reuters reported. Children, pregnant women, and hospitalized patients should stay out of some areas 12-18 miles from the Fukushima nuclear complex, he added.
Government officials the new evacuation plans "are meant to ensure safety against risks of living there for half a year or one year."
Because concern centers on long-term exposure, residents can abandon their homes in a leisurely fashion.