A strong aftershock with a preliminary magnitude of 7.0 jolted east and northeast Japan on Monday, killing one man, disrupting vital cooling operations at the crippled Fukushima nuclear plant, and knocking out power to about 220,000 households.
The epicenter of the quake was about 30 km west-southwest of Iwaki, Fukushima Prefecture, where it struck at a depth of only 6 km.
The temblor cut off external power to the pumps serving reactors 1, 2, 3 at around 5:16 p.m., but Tokyo Electric Power Co. revived power and resumed pumping operations at 6:05 p.m., according to the Nuclear and Industrial Safety Agency.
If the water injection is stopped for hours, the red-hot reactors will heat up again as they did after the March 11 tsunami wiped out the plant’s cooling systems, causing its damaged fuel rods to melt further.
Monday’s aftershock renewed fears about the state of the reactors, which Tepco must perpetually douse as it works to restore their cooling systems and shut them down. The unfortunate side effect of that tactic has been radioactive runoff.
The quake registered lower 6 in parts of Fukushima and Ibaraki prefectures on the Japanese seismic intensity scale to 7, prompting workers at the power plant to evacuate.
There were no reports of damage to nuclear power plants in Ibaraki, Niigata, Miyagi and Aomori prefectures.
More than 400 aftershocks of magnitude 5.0 or greater have struck since the March 11 quake.
Keiji Dohi, a quake predictor at the Meteorological Agency, warned Monday that the public should assume that an aftershock maxing out at 7 on the Japanese scale could hit eastern Japan “for the time being.”
A 46-year-old man in Ryugasaki, Ibaraki Prefecture, died after falling down and hitting his head, the local fire department said, adding that at least five people were injured in Ibaraki and one in Tochigi.
In Iwaki, Fukushima Prefecture, a family of four escaped death after a mudslide triggered by the quake buried their house. They were later rescued, according to Fukushima Prefectural Government.
East Japan Railway Co. temporarily suspended bullet trains on the Tohoku, Joetsu, Nagano and Yamagata shinkansen lines, while the Tohoku Expressway was closed between Shirakawa in Fukushima and Shiroishi in Miyagi Prefecture.