The US Geological Survey says the earthquake was centred around seven miles (12km) north of Alaska’s largest city, Anchorage.
The National Tsunami Warning Centre issued a tsunami warning for coastal zones of southern Alaska but it has since been cancelled.
US President Donald Trump said Alaska had been hit hard by a ‘big one’ and the federal government would spare no expense in its response to the earthquake.
To the Great people of Alaska. You have been hit hard by a big one. Please follow the directions of the highly trained professionals who are there to help you. Your Federal Government will spare no expense. God Bless you ALL!
As the quake hit, people ran out of buildings or sought shelter under office desks.
People went back inside buildings later before a smaller aftershock sent them running back into the streets again.
There were no immediate reports of any deaths or serious injuries.
Police in Alaska’s Kodiak island community – about 200 miles (321km) south of Anchorage – told residents to head to higher ground amid the tsunami threat.
The Anchorage Police Department said they were operational after Friday’s massive earthquake.
There is major infrastructure damage across Anchorage, it said.
Many homes and buildings are damaged.
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Hank Graper, a lawyer working and living in Anchorage, said he saw traffic poles swaying and called it the most violent quake he had experience in his 20 years in the city.
Pictures posted to social media sites showed damage that included collapsed ceiling tiles at an Anchorage high school and buckled roadway pavement in places.
KTVA’s newsroom felt the blow of the earthquake this morning. #anchorage #alaska #earthquake #weather pic.twitter.com/d1SaxriGw9
One photo shows a newsroom based in the city that felt the blow of the earthquake.
Another showed a car in the middle of a collapsed road.
Cereal boxes and packages of batteries littered the floor of a supermarket and picture frames and mirrors were knocked from living room walls.
#HolyCrap #Earthquake #anchorage pic.twitter.com/88MR0UVO3C
Alaska averages 40,000 earthquakes per year, with more large quakes than the other 49 states combined.
Southern Alaska has a high risk of earthquakes due to tectonic plates sliding past each other under the region.
On 27 March 1964, Alaska was hit by a magnitude 9.2 earthquake, the strongest recorded in US history.
It centred about 75 miles (120km) east of Anchorage and lasted about four-and-a-half minutes. The tsunami it triggered claimed about 130 lives.
News Source SkyNews