TOKYO — Japan was rattled by a strong aftershock and tsunami warning Thursday nearly a month after a devastating earthquake and tsunami flattened the northeastern coast. Announcers on Japan’s public broadcaster NHK told coastal residents to run to higher ground and away from the shore.

The Japan meteorological agency issued a tsunami warning for a wave of up to 6 feet after the magnitude-7.4 aftershock. The warning was issued for a coastal area already torn apart by last month’s tsunami, which is believed to have killed some 25,000 people and has sparked an ongoing crisis at a nuclear power plant.

Officials at the tsunami-ravaged Fukushima Dai-ichi nuclear plant said there’s no immediate sign of new problems caused by the aftershock. Plant operator Tokyo Electric Power Co. said it evacuated two workers there and seven at a sister plant to the south that was not badly damaged.

Officials say Thursday’s aftershock hit 16 miles under the water and off the coast of Miyagi prefecture. The quake that preceded last month’s tsunami was a 9.0-magnitude.
Buildings as far away as Tokyo shook for about a minute.

In Ichinoseki, inland from Japan’s eastern coast, buildings shook violently, knocking items from shelves and toppling furniture, but there was no heavy damage to the buildings themselves. Immediately after the quake, all power was cut. The city went dark, but cars drove around normally and people assembled in the streets despite the late hour.

Paul Caruso, a geophysicist at the U.S. Geological Survey in Golden, Colo., said Thursday’s quake struck at about the same location and depth as the March 11 quake. It’s the strongest of the more than 1,000 aftershocks that have been felt since, except for a 7.9 aftershock that day.
The USGS said the aftershock struck off the eastern coast 40 miles from Sendai and 70 miles from Fukushima. It was about 205 miles from Tokyo.

A Pacific Tsunami Warning Center evaluation of the quake said an oceanwide tsunami was not expected. However, it noted quakes of that strength can cause waves that are destructive locally.