Alaska quake: Residents fled to higher ground over tsunami fears

Headlights from a line of cars shine at dusk as people evacuate the Spit in Homer, Alaska, following a powerful earthquake that prompted a tsunami warning. Photo / AP

A powerful earthquake off Alaska's southern coast jolted sparsely populated coastal communities last night NZT, and some residents briefly fled to higher ground over fears of a tsunami.

There were no immediate reports of damage in the Alaska Peninsula and the tsunami warning was cancelled after the magnitude 7.8 quake offshore produced a wave of a less than 30cm.

According to the US Geological Survey, the earthquake was centered in waters 105km south-southeast of the tiny community of Perryville, at a depth of 28 km.

Because of the temblor's location, some nearby Alaska Peninsula communities did not experience shaking that would normally be associated with the quake's magnitude, said Michael West, Alaska state seismologist.

It has been a rocking overnight with multiple sizeable earthquakes. 7.8 tremor just before midnight (Pacific Time) off the Alaska Coast, and a 6.2 tremor to the NW of Seattle just before 5am. No tsunami risks with either. #cawx pic.twitter.com/4wOeRc2Axk

— Eric McCormick (@Eric_In_The_PNW) July 22, 2020

Residents in some small towns within 160km of the quake reported very strong shaking and some shaking was felt more than more than 805km away in the Anchorage area, West said.

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 about 320km northeast of the epicentre, the local high school and the Catholic church opened their doors for evacuees and the school parking lot was declared a safe zone, with some people staying in their cars with pets until it was safe to go home.

"No reports of any damage," said Kodiak police Sergeant Mike Sorter. "No injuries were reported. Everything is nominal."

Watch the waves from the M7.8 Alaska earthquake roll across seismic stations in North America! #AlaskaEarthquake (THREAD) pic.twitter.com/GOcPFbduy7

— IRIS Earthquake Sci (@IRIS_EPO) July 22, 2020

Gerry Cobban Knagin took video of the parking lot scene at Kodiak Aleutian Regional High School, where 300 or 400 other people were sheltering.

By today, she was ready to take part in a hike in Kodiak.

"We adjust quickly here. Life is back to normal," she said in a Facebook message before heading out to Pyramid Mountain with friends.

Officials at the National Tsunami Warning Centre in Palmer, Alaska, began calling off the tsunami advisories and warnings after a wave of less than 30cm 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.

The 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.

Humpback whales in Alaska have been swimming in quieter waters during the pandemic, as ship traffic has fallen.

Scientists say it’s a once-in-a-lifetime chance to listen to whales without the impact of human noise.https://t.co/Uijza4HIEZ pic.twitter.com/ycgmEEQciF

— NPR (@NPR) July 22, 2020

More than a dozen aftershocks of magnitude 4.0 or higher were reported immediately after the earthquake.

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

The earthquake happened in the so-called Alaska-Aleutian Trench, where a magnitude 9.2 quake in 1964 occurred.

That remains the second most powerful earthquake ever recorded globally. 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 US state. Nearly 25,000 earthquakes have been recorded in Alaska since January 1.

- AP