Japan lifted all tsunami alerts after a magnitude 7.4 earthquakeoff the coast of Fukushima, home to the nuclear power plantcrippled in the March 2011 triple disaster.

The temblor, an aftershock of the magnitude 9 quake five yearsago, briefly knocked offline a cooling system for spent nuclearfuel at a separate Fukushima plant, and prompted authorities toissue the highest tsunami warnings for five years.

It struck at 5:59 a.m. local time Nov. 22 at a depth of 25kilometers (15.5 miles), according to the Japan MeteorologicalAgency, causing a tsunami of more than one meter on the coast ofMiyagi prefecture and smaller waves elsewhere.

Related: How parametric insurance can help after naturalcatastrophes

Aftershocks expected

The weather agency warned that aftershocks of a similar size to thequake could occur over the next week, triggering further tsunamis,public broadcaster NHK reported. A similar-sized quake struck theregion two days before the March 2011 disaster that killed about18,000 people.

Local authorities and NHK initially urged residents to rememberthe experience of five years ago and flee to higher ground.

Five people have been reported injured, mostly in northeasternJapan, according to the Fire and Disaster Management Agency. Somebullet train services were suspended and Sendai Airport wasevacuated, but Toyota Motor Corp. plants in the region wereoperating as normal.

A cooling system for a spent fuel pool at the Fukushima Dai-Niplant shut down automatically after the quake, triggering memoriesof the early moments following the 2011 disaster, but was restartedless than two hours later. The stoppage of the system, which pumpswater to a pool storing 2,544 nuclear fuel rods, would notimmediately have led to a release of radiation, Chief CabinetSecretary Yoshihide Suga said before the restart.

Power would need to be cut for about a week before temperaturesin the spent-fuel cooling system would reach the upper safetylimit, according to Yutaka Ikoma, a spokesman at the NuclearRegulation Authority. Temperatures would rise about 0.2 degreesCelsius per hour without the cooling system, reaching 65 degreesCelsius in about seven days, according to the spokesman.

Workers at the Dai-Ichi nuclear plant, crippled following in the2011 disaster, were evacuated as a precaution after the quake,according to a spokesman.

Suga told reporters in Tokyo that the cause of the pump’smalfunction was under investigation, and added that Japan has thestrictest nuclear regulations in the world.

“These regulations envisage the largest earthquake that couldoccur on the site of a nuclear plant, and confirm that safety willbe assured through individual inspections,” Suga said. “Tsunami andother natural disasters are also among the possibilities that areenvisaged under the new regulations. The government will maintainsafety as the top priority in dealing with nuclear plants.”

Related: New Zealand earthquake seen costing insurers up to$3.7 billion

Prime Minister Abe’s goal

More than five years after the quake, just two of the country’s 42reactors are in operation. Returning the plants to service is agoal of Prime Minster Shinzo Abe’s government that aims to havenuclear account for as much as 22 percent of the nation’s energymix by 2030. Abe, speaking from Argentina where he is making anofficial visit, said he ordered ministries to gather informationand formulate a response.

Tuesday’s malfunction at the nuclear plant won’t help thegovernment in its goal to restart the reactors, said Daniel P.Aldrich, a professor at Northeastern University’s Security andResilience Studies Program. The public is against restarts“primarily because the Fukushima meltdowns revealed the falsity ofthe 100 percent safety myth promoted by the nuclear power utilitiesand the central government regulators,” Aldrich said.

Adam Pascale, a seismologist with the Seismology Research Centrein Melbourne, played down any connection between Tuesday’s quake inJapan and the magnitude 7.8 shaker in New Zealand lastweek.

“Whenever you have two big earthquakes or several bigearthquakes in close time proximity, people immediately think thatthere is a cause and effect thing, but these things happen all thetime,” Pascale said. “There are stress changes throughout the Earthwhen you do have an earthquake, but the amount of shaking that NewZealand generated and the amount of ground movement in Japan wouldhave been insignificant in terms of generating another fault.”

Copyright 2018 Bloomberg. All rightsreserved. This material may not be published, broadcast, rewritten,or redistributed.