ANCHORAGE, Alaska (AP) — A powerful earthquake off Alaska’s southern coast jolted coastal communities late Tuesday, and some residents briefly scrambled for higher ground over fears of a tsunami.

There were no immediate reports of damage in the sparsely populated area of the state, and the tsunami warning was cancelled after the magnitude 7.8 quake off the Alaska Peninsula produced a wave of a less than a foot.

According to the US Geological Survey, the earthquake struck Tuesday at 10:12 pm local time and was centred in waters 65 miles (105 kilometres) south-southeast of the tiny community of Perryville, at a depth of 17 miles (28 km).

Because of the temblor’s location, nearby communities along the Alaska Peninsula did not experience shaking that would normally be associated with that magnitude of a quake, said Michael West, Alaska State Seismologist.

That doesn’t mean they slept through it, West said residents in small towns within a hundred miles (160 kilometres) of the quake reported very strong shaking. Some shaking was also felt more than 500 miles (805 kilometres) away in the Anchorage area, West said.

“No reports of any damage,” Kodiak Police Sgt Mike Sorter said early Wednesday morning. “No injuries were reported. Everything is nominal.”

Kodiak is about 200 miles (320 kilometres) northeast of where the earthquake was centered.

The tsunami warning prompted coastal residents to evacuate to higher ground, with social media posts showing long lines of people fleeing towns like Homer and Kodiak as tsunami sirens wailed in the background.

On Kodiak Island, the local high school and Catholic opened their doors for evacuees, the Anchorage Daily News reported.

“We’ve got a high school full of people,” said Larry LeDoux, superintendent of the Kodiak School District. “I’ve been passing out masks since the first siren sounded,” he told the Daily News.

“Everything’s as calm as can be. We’ve got probably 300, 400 people all wearing masks,” he said before the warning was cancelled.

Tsunami warnings are commonplace for people who grew up in Kodiak.

”I’ve been doing these since I was a little kid,” LeDoux told the newspaper. “Old news.”

Officials at the National Tsunami Warning Centre in Palmer, Alaska, began calling off tsunami advisories and warnings after a wave of less than 1 foot (30 centimetres) was recorded in the community of Sand Point.

“I might have expected a little bit more water, but I’m happy that there wasn’t,” said David Hale, the senior duty scientist at the tsunami centre.

Tuesday’s quake was more powerful than the magnitude 7.1 earthquake that caused damage in the Anchorage area in November 2018.

“This earthquake released about 15 times as much energy as that earthquake, said West, the state seismologist.

More than a dozen aftershocks of magnitude 4.0 or higher were reported immediately after the earthquake, he said from the Alaska Earthquake Centre at the University of Alaska Fairbanks.

”We got people here who are going be working all night,” West said early Wednesday morning. ”These aftershocks will go and go and go and go.”

The Alaska-Aleutian Trench was also where a magnitude 9.2 quake in 1964 was centred. That remains the second most powerful earthquake ever recorded. The temblor and ensuing tsunami caused widespread damage and killed 131 people, some as far away as Oregon and California.

Alaska is the most actively seismic state. Nearly 25,000 earthquakes have been recorded in Alaska since January 1, according to the centre.