By Lauren Kent, Yumi Asada

(CNN) — The Japanese government has warned of a slightly heightened risk of a megaquake in the next week after a strong 7.4-magnitude earthquake struck off the country’s northeastern coast on Monday, triggering a tsunami warning, according to the Japan Meteorological Agency and the US Geological Survey.

The three-meter (9.8-foot) tsunami warning was issued following the quake, but the threat was later revised down to a tsunami advisory before being lifted altogether, authorities said.

Now residents in 182 towns across seven prefectures have been urged to be on alert for a potential stronger earthquake and to confirm evacuation routes and shelters, Japan’s national broadcaster NHK reported.

The megaquake advisory is not a prediction, but officials from Japan’s Cabinet Office and the Japan Meteorological Agency said there was a 1% chance of an earthquake of magnitude 8 or stronger striking along two deep sea trenches in the Pacific in the next week, compared to a 0.1% chance during normal times, the Associated Press reported.

A similar advisory was issued following a 7.5-magnitude earthquake that struck off Japan’s northeastern coast in December 2025, but a larger quake did not occur.

“The government will do our utmost in case of an emergency,” Japanese Prime Minister Sanae Takaichi told reporters Monday, the AP reported.

Monday’s earthquake prompted the country’s disaster management agency to issue evacuation orders to more than 180,000 people.

CNN’s producer on the ground in Tokyo reported feeling the building they were in shake for about seven minutes when the earthquake struck.

Two people were injured after falling, according to Japan’s Fire and Disaster Management Agency, the AP reported. But no damage to homes had been recorded, chief cabinet secretary Minoru Kihara said Monday evening local time, noting the situation was still being assessed. Kihara added that there were 200 power outages across the impacted areas and authorities were working to restore service.

The Japan Meteorological Agency initially issued a three-meter tsunami warning for the Iwate prefecture and parts of Hokkaido and Aomori – later downgraded to an advisory. It also issued an advisory in other areas of northeastern Japan, estimating a tsunami of up to one meter (3.3 feet).

Observations of tsunami waves were well below the warning level that was issued. One 0.8-meter (2.6-foot) tsunami struck Kuji Port in Iwate Prefecture, according to data from the meteorological agencies. Another 0.4-meter (1.3-foot) tsunami hit Miyako Port in Iwate Prefecture.

The US Tsunami Warning System reported that the magnitude of the earthquake off the east coast of Honshu, Japan, was 7.4. The tsunami threat was issued at 8:52 UTC (4:52 a.m. ET). Japan’s national agency later revised its figure up to 7.7 magnitude, although it’s unclear why there is a discrepancy in the numbers.

Prime Minister Takaichi urged residents in affected areas to evacuate immediately and said the government had set up an emergency task force.

Authorities were doing their “utmost to assess the damage, implement emergency disaster response measures such as search and rescue operations, and provide timely and accurate information to the public,” Takaichi said.

During a tsunami warning, waves of up to three meters are expected and would cause damage to low-lying areas. A tsunami advisory is the lowest-level alert, and is issued when waves of up to one meter are expected. At that alert level, the Japan Meteorological Agency warns that anybody exposed will be caught in strong tsunami currents, and it advises people to leave coastal areas immediately.

Bullet train services resumed their operations Monday evening after suspending operations due to power outages caused by the earthquake, NHK reported Tuesday. Affected trains included services between Tokyo and Shin-Aomori stations, Akita and Morioka stations in northern Japan, and local trains in Iwate prefecture, according to NHK.

Tokyo Electric Power Company said in a statement that no abnormalities had been detected at its Fukushima Daiichi and Fukushima Daini nuclear power plants, although it evacuated workers. The Tohoku Electric Power Company said that its Onagawa nuclear plant and Higashidori nuclear plant further north have also not experienced abnormalities, with radioactive material levels still within normal range.

Japan is one of the most earthquake-prone countries in the world. It lies on the Ring of Fire, an area of intense seismic and volcanic activity on both sides of the Pacific Ocean. The worst quake in recent Japanese history was the 9.1-magnitude Tohoku earthquake in 2011, which triggered a major tsunami and nuclear disaster.

“Japan is one of the least surprising places on Earth for an event like this. Statistics show that about 10% of the world’s earthquakes occur in and around Japan,” said hydrodynamics expert Ioannis Karmpadakis, an associate professor in coastal engineering at Imperial College London.

He added that Japan also accounts for roughly 20% of the world’s magnitude-6+ earthquakes.

“Even waves that do not look dramatic can still be dangerous,” Karmpadakis added in a statement. “A tsunami does not need to be towering to cause harm: the real danger is fast-moving water surging in and out, creating currents strong enough to knock people over, damage boats and push water up rivers and into harbours.”

This story has been updated with additional developments.

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