OTOMAKASSAR – A magnitude-7.4 earthquake off Fukushima Prefecture rocked widespread areas early Tuesday, triggering tsunami warnings along the Pacific coast and briefly stopping a nuclear reactor fuel pool’s cooling system.
The temblor, an aftershock from the magnitude-9.0 Great East Japan Earthquake, which struck on March 11, 2011, had registered a preliminary magnitude of 7.3 but was revised to 7.4, the Meteorological Agency said.
The tsunami warnings were later downgraded to advisories.
Shortly after the quake hit, Chief Cabinet Secretary Yoshihide Suga told an emergency news conference at the Prime Minister’s Office that the reactor 3 nuclear fuel pool cooling system stopped at Tepco’s Fukushima No. 2 plant, where 2,544 spent nuclear fuel rods are. “We have been informed that there is no immediate risk of radiation leaks or rise in the temperatures (of the cooling pool),” Suga said.
NHK later reported that the cooling pump had been reactivated and cooling had resumed at Fukushima No. 2. Tepco said on its website that the magnitude-7.4 quake suspended the cooling system at around 6:10 a.m., but the system was restarted at 7:47 a.m.
Tsunami warnings were issued along the Pacific coast, including in Aomori, Iwate, Ibaraki and Chiba prefectures. A later tsunami warning was also issued for Miyagi Prefecture as well.
The Fukushima and Miyagi warnings were later lifted.
A 1.4-meter tsunami was observed at Sendai port at 8:03 a.m. The 1.4-meter tsunami observed at Sendai was the largest since the March 11, 2011, megaquake, the agency said.
People were told to evacuate immediately to high ground in Fukushima Prefecture, where waves had been forecast to reach 3 meters.
NHK reported that the city of Minami-sona, Fukushima Prefecture, ordered all of its 68,000 residents to evacuate in response to the tsunami warning. Five evacuation centers had been set up in the city, where 150 people fled.
The Meteorological Agency warned of tsunami of up to 1 meter in Aomori, Iwate, Miyagi, Ibaraki and Chiba prefectures, urging people to stay away from coastal areas.
According to the agency, tsunami of 90 cm were observed in the city of Soma, Fukushima Prefecture, at 7:06 a.m., while in Oarai, Ibaraki Prefecture, tsunami of 50 cm were observed at 7:08 a.m.
Kyodo quoted the agency as saying tsunami of 60 cm were observed in Onahama in the city of Iwaki, Fukushima Prefecture.
Authorities had warned people to keep alert until the tsunami warnings were lifted, because the waves could hit more than once.
The tsunami advisory for Aomori, Chiba and the Izu Islands was later lifted.
The Meteorological Agency said the earthquake earlier Tuesday was an aftershock of the magnitude-9.0 temblor that hit the Tohoku region in 2011. Even though the scale of the tremors has become much smaller compared to the ones right after the 3/11 earthquake, an agency representative said the seismic activities are still active enough to cause an M.7-class earthquake once a year. The last time an M.7-class aftershock rattled the Tohoku region was in July 2014, according to the agency.
Fukushima Prefectural Police said a fire broke out at a petrochemical complex in the city of Iwaki but was put out in about 25 minutes. No one was injured.
Also, a woman in her 70s was reported injured in the town of Yabuki, Fukushima Prefecture, suffering cuts to the back of her head when dinnerware fell from a cupboard.
The 5:59 a.m. temblor had an intensity of minus-5 on the Japanese seismic scale to 7.
The magnitude-7.4 tremor was followed by a magnitude-5.4 quake off Fukushima Prefecture at around 6:10 a.m. that registered shindo-3 in Fukushima and Miyagi prefectures, and a magnitude-5.5 tremor hit at around 6:39 a.m. in Fukushima Naka-dori that also registered shindo-3 in parts of Fukushima and Ibaraki.
Earlier reports said Tokyo Electric Power Co. Holdings was checking if the crippled Fukushima No. 1 nuclear plant, and nearby No. 2 plant, both of which have been shut down since the 2011 mega-quake, were affected.
Kyodo News said Tepco confirmed the Fukushima No. 1 plant was not affected.
According to NHK, the cooling equipment for the spent nuclear fuel pool in the reactor 3 building of Tepco’s Fukushima No. 2 nuclear plant stopped. The reactor has 2,544 spent nuclear fuel rods.
Kyodo also said Tohoku Electric Power Co.’s Onagawa nuclear power plant, which straddles the towns of Onagawa and Ishinomaki, Miyagi Prefecture, was not affected. The plant is also offline.
The Tokai No. 2 nuclear plant in the village of Tokai, Ibaraki Prefecture, also did not report any abnormality.
East Japan Railway Co. suspended some operations on the Tohoku, Joetsu and Hokuriku Shinkansen lines, while JR Tokai suspended services between Tokyo and Toyohashi stations.
JR Tokai said the Tokaido Shinkansen Line resumed operations at 6:18 a.m.
The Meteorological Agency said the quake struck around 6 a.m at a depth of 10 km (6 miles). The U.S. Geological Survey measured the magnitude at 6.9. The earthquake shook buildings in Tokyo, 240 km (150 miles) southwest of the epicenter.
The Fukushima No. 1 nuclear plant was destroyed by huge tsunami following the March 2011 offshore earthquake, leading to three reactor core meltdowns.(kyodo/ap))