Coastal residents fled their homes for higher ground after a powerful 8.2 magnitude earthquake triggered a tsunami warning for parts of the Pacific Ocean.
Forecasters had predicted tsunami waves of about 4-5ft for sections of Alaska's coastline, but later said the waves would be less than a foot as the warning was cancelled.
Tsunami sirens went off in the city of Kodiak, Alaska, after the north-western US state was rocked by the strongest tremor this year and the largest in America for more than 50 years.
Residents felt the ground shake and received tsunami warning alerts on their mobile phones about five minutes later, telling them to immediately move away from the water.
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A tsunami warning for parts of Alaska was cancelled about two hours after the earthquake hit.
A tsunami watch for Hawaii, some 2,500 miles away, was also lifted.
Almost 7,000 miles away in New Zealand, officials assessed the potential threat and later said coastal flooding was not expected there.
Initially estimated at magnitude of 7.2 and then 8.1, the shallow undersea earthquake struck at a depth of about 20 miles, roughly 55 miles south-east of Perryville, on the Alaska Peninsula.
It hit at about 10.30pm local time on Wednesday (6.15am GMT on Thursday) and was followed by powerful undersea aftershocks as strong as 6.2, occurring about 85 miles from the city of Chignik.
Jennifer Sonne shared a video clip which captured the sound of a siren as she and colleagues fled to higher ground in Kodiak.
Ms Sonne, who lives in Anchorage and was in Kodiak for work with an environmental consulting company, told the Mirror there was heavy traffic as evacuees went to safer places away from the coast.
She said: "We felt the earthquake about five to 10 minutes before we received the tsunami warning on our phones.
"I was loading the dishwasher in our rental house and my colleague noticed the earthquake and said 'did you feel that?'
"And I didn’t at first but I looked out the window and say trees moving. It felt very low frequency.
"The house we are staying in is on the coast, so at first we thought we could stay out and watch the water, but our team member from Kodiak told us it was the real thing and that we should evacuate.
"So we left the rentals house for higher ground and joined other cars, bicyclists, and pedestrians moving to higher ground. We are now evacuated and safe at our co-worker’s sister’s house.
"Usually traffic here is pretty minimal, but traffic was as heavy as I’ve seen even at nearly 11pm."
She added: "I feel very excited but in no real danger, so I feel like I’m reliving history. I just read the book 'This is Chance!' by Jon Mooallem and it makes me feel like I’m where the ‘64 quake tsunami occurred.
"I experienced the big 2018 earthquake in Anchorage and this did not feel as dramatic. But I’ve never been where a tsunami danger was real."
This is Chance! tells the story of the Great Alaskan Earthquake, a 9.2 magnitude tremor which hit near Prince William Sound and was the largest ever felt in the US, triggering tsunami waves as high as 220ft and killing more than 130 people on Good Friday (March 27) in 1964.
In that event, tsunamis cause damage as far away as Hawaii and Japan.
Following Wednesday's earthquake, the US National Tsunami Warning Center urged people living within the warning area to immediately leave their homes for higher ground.
Jared Rackley, a National Weather Service meteorologist visiting from Pittsburgh, fled his campsite just 30ft from the sea and went to a high school that was being used as a shelter for displaced residents and tourists.
Mr Rackley tweeted: "Camping literally 30ft from the coast in Seward, AK tonight. My first ever tsunami warning. We evaced to the local high school."
Patrick Mayer, a school superintendent who lives in Sand Point,told the Anchorage Daily News he was sitting in his kitchen when his house started to shake
He said:. “It started to go and just didn’t stop.It went on for a long time and there were several aftershocks, too.
"The pantry is empty all over the floor, the fridge is empty all over the floor.”
Mr Mayer said he went to the local school as part of the evacuation. About 300 evacuees had gathered at a school in King Cove.
Michael Ashley, who lives in Cold Bay, told the newspaper that the ground “rolled for a pretty good amount of time,” but it wasn't as severe as a 7.8 magnitude earthquake that hit the region last year.
In the since-expired warning, the National Tsunami Warning Center said: "Evacuate inland or to higher ground above and beyond designated tsunami hazard zones or move to an upper floor of a multi-story building depending on your situation.
"A tsunami with damaging waves and powerful currents is possible.
"Repeated coastal flooding is possible as waves arrive onshore, move inland, and drain back into the ocean.
"Strong and unusual waves, currents and inland flooding can drown or injure people and weaken or destroy structures on land and in water.
"Water filled with floating or submerged debris that can injure or kill people and weaken or destroy buildings and bridges is possible.
"Strong and unusual currents and waves in harbours, marinas, bays, and inlets may be especially destructive."
The warning was issued for South Alaska, the Alaska Peninsula and the Aleutian Islands.
Advisories were issued for other parts of Alaska's coastline, which sits on the Pacific Ring of Fire, while Hawaii was placed under a tsunami watch.
Countries as far away as Japan and New Zealand were assessing the potential threat in the immediate aftermath of the earthquake.
New Zealand's National Emergency Management Agency tweeted: "We are assessing whether the M8.1 ALASKA PENINSULA earthquake poses any tsunami threat to New Zealand.
"If a tsunami has been generated it is not likely to arrive in New Zealand for at least 12 hours."
It wrote more than an hour later: "Coastal inundation (flooding of land areas) is not expected following the ALASKA PENINSULA earthquake.
"People do not need to evacuate unless directly advised by local civil defence authorities."
Japan also said the tsunami posed no threat to its coastal communities.
Powerful 7.8 and 7.6 earthquakes hit the same region of Alaska in July and October of last year.
Wednesday's 8.2 magnitude earthquake is the strongest one recorded so far in 2021, edging an 8.1 tremor off New Zealand's Kermadec Islands on March 4.
It is the largest quake to hit the US since an 8.7 magnitude tremor hit the Rat Islands in Alaska on February 3, 1965, and has equalled two other 8.2 events - both in Alaska in September 1899 - as the sixth strongest earthquake in American history.
Alaska sits on the Ring of Fire, a horse-shoe shaped band of volcanoes and fault lines circling the edges of the Pacific Ocean and stretching some 25,000 miles long.
Its seismic activity results from collisions between tectonic plates.
It has the world's largest number of historically active volcanoes, according to the US Geological Survey (USGS), making it prone to earthquakes and other volcanic disruptions.
