Powerful Earthquakes Buckle Roads In Alaska

Back-to-back earthquakes measuring 7.0 and 5.8 have rocked buildings and buckled roads in Anchorage, Alaska, prompting people to run from their offices or take cover under desks.

The US Geological Survey says the first and more powerful quake was centred about 12 kilometres north of Anchorage, Alaska's largest city.

An automatically generated tsunami warning for coastal areas of southern Alaska was cancelled, after residents on Kodiak Island were earlier told to flee to higher ground.

Photographs posted to social media sites showed damage including buckled roads and collapsed ceiling tiles at an Anchorage high school.

A car was trapped on a collapsed section of the offramp in Anchorage. Image: AAP

One image showed a car stranded on an island of pavement, surrounded by cavernous cracks where the earthquake split the road.

People went back inside buildings after the first earthquake struck, but the 5.8 aftershock about five minutes later sent them running back into the streets. Alaska averages 40,000 earthquakes per year, with more large quakes than the 49 other US states combined.

Southern Alaska has a high risk of earthquakes because of tectonic plates sliding past each other under the region.