A massive earthquake, among the strongest ever recorded, hit Russia’s Far East on Wednesday, triggering tsunami waves that reached Japan, Hawaii, and the U.S. West Coast. While significant damage hasn’t been reported, authorities have advised the public to stay away from the coasts as the threat may persist for over a day.

Ports on Russia’s Kamchatka Peninsula, near the quake’s 8.8 magnitude epicenter, experienced flooding, forcing residents to move inland. In northern Japan, foamy waves surged to the beaches, while in Hawaii’s capital, traffic congestion occurred even in inland areas.

In Japan, people sought refuge in evacuation centers, mindful of the devastating 2011 earthquake and tsunami that led to nuclear meltdowns. Fortunately, no irregularities were found at Japan’s nuclear facilities on Wednesday.

Russian authorities said several people were injured, without giving a figure. In Japan, at least one person was injured.

Tsunami waves measured between 3 to 4 meters (10 to 13 feet) in Kamchatka, 60 centimeters (2 feet) on Hokkaido, Japan’s northern island, and just under 30 centimeters (1.4 feet) above normal tide levels in Alaska’s Aleutian Islands.

Several hours post-quake, Hawaii downgraded its tsunami warning to an advisory, as did Japan’s Meteorological Agency for areas south of Fukushima along the Pacific coast, although a heightened advisory remains for the northern regions.

According to Maj. Gen. Stephen Logan, of the State of Hawaii Department of Defense, an advisory indicates the likelihood of strong currents, perilous waves, and potential flooding on beaches or in harbors.

Hawaii and Oregon warn residents of potential damage

The impact of the tsunami could last for hours or perhaps more than a day, said Dave Snider, tsunami warning coordinator with the National Tsunami Warning Center in Alaska

“A tsunami is not just one wave,” he said. “It’s a series of powerful waves over a long period of time. Tsunamis cross the ocean at hundreds of miles an hour — as fast as a jet airplane — in deep water. But when they get close to the shore, they slow down and start to pile up. And that’s where that inundation problem becomes a little bit more possible there.”

“In this case, because of the Earth basically sending out these huge ripples of water across the ocean, they’re going to be moving back and forth for quite a while,” which is why some communities may feel effects longer, he said.

Hawaii Gov. Josh Green said data from Midway Atoll, which is between Japan and Hawaii, measured waves from peak to trough of 6 feet (1.8 meters). He said waves hitting Hawaii could be bigger or smaller and it was too early to tell how large they would be. A tsunami of that size would be akin to a 3-foot (90-centimeter) wave riding on top of surf, he said.

“This is a longitudinal wave with great force driving through the shoreline and into land,” he said at a news conference.

Green said Black Hawk helicopters have been activated and high-water vehicles were ready to go in case authorities need to rescue people. “But please do not put yourself in harm’s way,” he said.

The Oregon Department of Emergency Management said on Facebook that small tsunami waves were expected along the coast starting around 11:40 p.m. local time, with wave heights between 1 to 2 feet (30 to 60 centimeters). It urged people to stay away from beaches, harbors and marinas and to remain in a safe location away from the coast until the advisory is lifted.

“This is not a major tsunami, but dangerous currents and strong waves may pose a risk to those near the water,” the department said.

Much of the West Coast, spanning California, Washington state, and the Canadian province of British Columbia, was also under a tsunami advisory.

A tsunami of less than 30 centimeters (under 1 foot) was forecast to hit parts of Vancouver Island, British Columbia. The province’s emergency preparedness agency said waves were expected to reach remote Langara Island around 10:05 p.m. Tuesday and Tofino around 11:30 p.m. The agency said “multiple waves over time” were expected.

Russian regions report limited damage

The quake at 8:25 a.m. Japan time had a preliminary magnitude of 8.0, Japanese and U.S. seismologists said. The U.S. Geological Survey later updated its strength to 8.8 magnitude and a depth of 20.7 kilometers (13 miles).

The quake was centered about 119 kilometers (74 miles) east-southeast from the Russian city of Petropavlovsk-Kamchatsky, which has a population of 180,000, on the Kamchatka Peninsula. Multiple aftershocks as strong as 6.9 magnitude followed.

Severokurilsk Mayor Alexander Ovsyannikov said the port in the city was flooded by tsunami waves, washing fishing boats into the sea. He said that no major damage was recorded.

Power supplies have been shut and the authorities were checking the power network after the flooding.

Among the world’s strongest recorded quakes

The earthquake appeared to be the strongest anywhere in the world since the 9.0 magnitude earthquake off northeastern Japan in March 2011 that caused a massive tsunami that set off meltdowns at a nuclear power plant. Only a few stronger earthquakes have ever been measured around the world.

The tsunami alert disrupted transportation in Japan, with ferries, trains and airports in the affected area suspending or delaying some operations.

A tsunami of 60 centimeters (2 feet) was recorded at Hamanaka town in Hokkaido and Kuji port in Iwate, according to the Japan Meteorological Agency. Several areas reported smaller waves including 20 centimeters (8 inches) in Tokyo Bay five hours after the quake.

In Japan’s northern coastal town of Matsushima, dozens of residents took refuge at an evacuation center, where water bottles were distributed and an air conditioner was running. One person told NHK she came to the facility without hesitation based on the lesson from the 2011 tsunami.

Japan’s Chief Cabinet Secretary Yoshimasa Hayashi warned evacuees that they may not be able to return home by the end of the day, as the tsunami waves could remain high.

Japanese nuclear power plants reported no abnormalities. The operator of the Fukushima Daiichi plant damaged by the 2011 tsunami said about 4,000 workers are taking shelter on higher ground at the plant complex while monitoring remotely to ensure safety.

Philippine authorities advised people to stay away from the beach and coastal areas. “It may not be the largest of waves, but these can continue for hours and expose people swimming in the waters to danger,” Teresito Bacolcol of the Philippine Institute of Volcanology and Seismology told The Associated Press.

Mexico’s navy warned that tsunami waves will start reaching the northern coast in Ensenada, near California, at around 02:22 a.m. Wednesday local time, and waves could progress along the Pacific coast to Chiapas state, around 07:15 a.m. local time.

New Zealand authorities warned of “strong and unusual currents and unpredictable surges” along all coastlines of the South Pacific island nation. The emergency management agency said people should move out of the water, off beaches and away from harbors, marinas, rivers and estuaries.

People were urged to stay away from coastlines until any wave surges passed late Wednesday in Fiji, Samoa, Tonga, Federated States of Micronesia and Solomon Islands.

Some tiny and low-lying Pacific island chains are among the world’s most imperiled by tsunamis and rising seas due to climate change.

Earlier in July, five powerful quakes — the largest with a magnitude of 7.4 — struck in the sea near Kamchatka. The largest quake was at a depth of 20 kilometers and was 144 kilometers (89 miles) east of the city of Petropavlovsk-Kamchatsky.