Strong earthquake hits off Japan’s coast, tsunami advisory issued

By Lauren Kent, Yumi Asada, CNN

(CNN) — A three-meter (9.8-foot) tsunami warning was issued for Japan on Monday after a strong 7.4 magnitude earthquake struck off the northeastern coast, according to the Japan Meteorological Agency and the US Geological Survey. The threat was later revised down to a tsunami advisory, authorities said.

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). The agency warned that aftershocks of a similar magnitude could happen in the coming week.

So far, observations of tsunami waves have been 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.

Japan’s disaster management agency said it had issued evacuation orders to 171,957 people in five prefectures.

No injuries or damage to homes have been recorded yet, chief cabinet secretary Minoru Kihara said in an update Monday evening local time, but the situation is still being assessed. Kihara added that there were 200 power outages across the impacted areas and authorities were working to restore service.

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

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

“Residents in areas where tsunami warnings have been issued should immediately evacuate to higher ground or safer locations such as evacuation buildings,” Takaichi told reporters in a news briefing on Monday, shortly after the earthquake.

Authorities are 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. “At this time, we are still confirming the extent of human and material damage, but we will receive detailed reports shortly and proceed with disaster response efforts.”

She later warned of the possibility of further advisories due to potential aftershocks off the coast of Hokkaido and Sanriku.

A tsunami advisory is the lowest-level alert, which 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.

The operator of the bullet train service that runs between Tokyo and Shin-Aomori station said the train had been suspended due to a power outage caused by the earthquake, Japan’s national broadcaster NHK reported. Train services have also been suspended between Akita Station and Morioka Station in northern Japan. All local trains in Iwate prefecture have halted services, 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 is a developing story and has been updated.

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CNN’s meteorologists Brandon Miller and Monica Garrett contributed to this report.