Japan’s meteorological agency said Thursday that there was a higher-than-usual chance that an immense earthquake could hit the country in the next few days, following a 7.1-magnitude temblor off the southern island of Kyushu.

Japan has long expected a major earthquake to occur along the Nankai Trough off its eastern coast. As of last year, researchers said there was a 60% chance that an earthquake of magnitude 8 to 9 — even more devastating than the one in 2011 that laid waste to the country’s northeast coast and knocked out cooling systems at the Fukushima Daiichi nuclear plant — would occur in the trough area over the next 20 years.

After the 7.1-magnitude quake Thursday, Japan’s meteorological agency convened a group of experts to evaluate whether it could be related to the long-anticipated bigger disaster, called a “Nankai Trough megathrust earthquake.”

Experts warn that an earthquake between two tectonic plates that converge along the Nankai megathrust fault, which runs from Kyushu north through Tokyo, could cause devastation. It could extensively damage cities throughout Japan, potentially cause a tsunami and lead to hundreds of thousands of deaths.

“The possibility of a large-scale earthquake occurring in the area of ​​the Nankai Trough is relatively higher than usual,” the meteorological agency said in a statement late Thursday.

The risk that an earthquake of magnitude of 8 or higher would occur after one with a magnitude of 7 is particularly elevated for about a week after the initial temblor, the agency said.

Japan’s meteorological agency issued a “caution” level of warning Thursday. The next step up would be an “alert,” which would advise residents to evacuate from areas deemed a tsunami risk. The agency said it was the first time Japan had issued a “caution.”

Prime Minister Fumio Kishida urged people to ensure that they were ready at all times in case an earthquake occurred and they had to evacuate. He told reporters that the government was on high alert.

Earlier Thursday, a tsunami advisory was issued for coastal regions on the southern Japanese islands of Kyushu and Shikoku after the 7.1-magnitude quake. As of late Thursday evening, the maximum height of waves recorded reached about a foot and a half off the coast of Miyazaki prefecture on Kyushu.

A handful of injuries but no deaths were reported related to the earthquake. Footage showed images of strong shaking in buildings in Miyazaki prefecture, but damage in the area appeared to be minimal. The earthquake occurred less than 20 miles off the coast of Miyazaki, according to the United States Geological Survey.

Bullet train service was temporarily halted on Kyushu, and the Miyazaki Airport suspended takeoffs and landings to inspect runways for any damage. Both bullet train and airport operations resumed later Thursday evening.

The Kyushu Electric Power Co. said its nuclear power plants were operating normally.

Separate from the heightened possibility of a Nankai Trough earthquake, Japan’s meteorological agency advised being alert for aftershocks of a similar magnitude off the eastern coast of Miyazaki prefecture over the next week. It said that landslides could also be a risk if there is rain in the coming days.

This article originally appeared in The New York Times.

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