TOKYO — A large earthquake shook a broad area across eastern Japan late Saturday night, with its epicenter off the coast of Fukushima, near where three nuclear reactors melted down after a quake and tsunami nearly 10 years ago.
The Japanese weather service reported the quake’s preliminary magnitude as 7.1, but said there was no danger of a tsunami.
Coming a little less than a month before the 10th anniversary of what is known as the Great East Japan earthquake, the quake rattled the greater Tokyo area for about 30 seconds starting at 11:08 p.m. and was felt powerfully in Fukushima and Sendai.
No serious damage was immediately reported, but the authorities warned residents to brace for aftershocks in the coming days.
The quake struck as Tokyo and nine other large prefectures are under a state of emergency to contain the coronavirus. Residents are encouraged to work from home and avoid going out at night, while restaurants and bars are closed at 8 each night.
Japan is also preparing to host the summer Olympics, postponed by a year from 2020. The Games are scheduled to open on July 23.
Authorities mobilize in response.
The prime minister’s office immediately set up a crisis management office and the Tokyo Electric Power Company, or Tepco, which operates the nuclear plants, said it was checking its monitoring posts in Fukushima to ensure that there were no radiation leaks.
Shortly after midnight, the public broadcaster NHK reported that Tepco had detected “no major abnormalities” at any of the Dai-ichi reactors where the meltdowns occurred in 2011 or at the Dai-ni plant a few miles away in Fukushima.
There was no immediate information about the hundreds of tanks filled with contaminated water stored on the Dai-ichi site. According to NHK, the Kashiwazaki-Kariwa nuclear plant on the west coast had suffered no damage.
According to Katsunobu Kato, chief cabinet secretary to Prime Minister Yoshihide Suga, about 950,000 households were left without power across the affected areas. Several bullet train lines have been suspended.
What the hours and days ahead may hold.
Speaking on NHK, Takashi Furumura, a professor at the Earthquake Research Institute at the University of Tokyo, warned that a quake of this size could be followed within two or three days by another of similar scale.
He said the epicenter of Saturday night’s quake was off the coast of Fukushima, likely about 37 miles below the sea.
In Minami Soma, one of the Fukushima villages evacuated after the nuclear disaster in 2011, NHK reported that severe horizontal shaking lasted for about 30 seconds on Saturday.
Yu Miri, the author of “Tokyo Ueno Station,” winner of the National Book Award for translated literature, posted photos on Twitter showing bookshelves in her nearby home downed and the floors strewn with books.
NHK reported that eight people had been injured in the Fukushima region.
Japan has endured a history of earthquakes.
Roughly a dozen powerful earthquakes have struck Japan in the last decade, several of them triggering tsunamis and landslides that have shaken parts of the country and destroyed countless buildings.
In 2016, more than 40 people died after two earthquakes rocked the southern island of Kyushu. The largest of the two registered a magnitude of 7.0, close to the intensity of the quake felt on Saturday, and several died in fires and landslides in the mountainous region.
In 2018, dozens died and millions lost power in their homes after a powerful quake in the northern island of Hokkaido triggered landslides. The quake that summer came just days after the largest typhoon recorded in 25 years struck Japan.
Makiko Inoue, Hisako Ueno, Hikari Hida and Elian Peltier contributed reporting.