TOKYO — A powerful aftershock 16 miles off northeastern Japan late Thursday disrupted power supplies to two nuclear facilities and complicated efforts to contain a monthlong emergency at a third, the Fukushima Dai-ichi nuclear power station.
Japanese television interrupted programming Thursday night to flash warnings of another tsunami, but the alert was later lifted.
The U.S. Geological Survey estimated the quake's magnitude at 7.1. It was the strongest aftershock since the March 11 magnitude-9.0 earthquake and tsunami that left as many as 12,600 dead and more than 14,700 missing.
Two people were killed and scores injured. Blackouts were seen throughout the northeastern coastal region of Honshu, Japan's main island, and two nuclear facilities lost much of their external power supply.
Electrical troubles at the Onagawa nuclear power station, north of Sendai, and a nuclear reprocessing plant farther north near a U.S. air base in Aomori prefecture did not appear to pose any risk of catastrophic failure.
Thursday's quake came just hours after a rare bit of good news — a successful operation to avert a possible explosion at a crippled reactor at Fukushima Dai-ichi by injecting nitrogen.
In Tokyo, 207 miles south of Thursday's epicenter, buildings swayed for more than a minute. Japan has experienced hundreds of aftershocks, but until Thursday none had exceeded a 6.6.
U.S. Evacuation zone: A recommendation for all U.S. citizens living within 50 miles of the crippled Fukushima Dai-ichi nuclear power plant to leave was based on incomplete information and assumptions about the reactors' condition, U.S. nuclear officials said Thursday in Washington. A Nuclear Regulatory Commission official said the decision was based on a "what if" calculation.
Information from the Associated Press was used in this report.