An earthquake with a preliminary magnitude of 6.5 struck southeast Hokkaido late Saturday, causing blackouts and prompting highway closures in some areas, the Meteorological Agency and local officials said.
The focus of the quake, which struck at 11:17 p.m. at a depth of about 108 km, was in the mountainous Tokachi region about 15 km southwest of Obihiro.
There were no reports of serious damage or problems at the three nuclear power facilities in the region, and only about a dozen people sustained injuries, most of them minor, they said.
No tsunami warnings were issued.
It is unclear whether the quake was related to the devastating Great East Japan Earthquake of March 2011, the Meteorological Agency said early Sunday.
The latest quake registered upper 5 on the Japanese seismic intensity scale to 7 in Kushiro, Nemuro and Urahoro in the east, and lower 5 in Obihiro and elsewhere the prefecture, as well as in Higashidori, Aomori Prefecture, on Honshu, the agency said.
The agency, which revised the magnitude from 6.4, advised residents to remain alert in the week ahead for aftershocks of around 4 on the Japanese scale.
The Pacific side of Hokkaido is no stranger to significant seismic activity. A 6.6-magnitude quake occurred in January 1987 near the epicenter of the latest one, and an 8-magnitude quake struck off the coast of Tokachi in September 2003.
“We cannot tell if the latest quake could touch off a bigger one. But please continue exercising caution,” agency official Akira Nagai said.
According to Hokkaido Prefectural Government officials, at least 12 people were slightly injured by Saturday night’s earthquake. Some fell down or were cut by breaking glass or other sharp objects, while others suffered burns or were hit by falling objects, they said.
Hokkaido Electric Power Co. said no abnormalities were detected at its nuclear power plant in the village of Tomari, in the southwest.
About 840 households in five municipalities, including Kushiro and Urahoro, temporarily lost power, local authorities said.
Some sections of the Doto and Obihiro-Hiroo expressways were briefly closed after the quake, the operator said.