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Tsunami warning
The red area on this map indicates the extent of the tsunami warning about an hour and a half after a magnitude-7.0 earthquake struck Alaska. ( / NOAA Graphic)

Buildings in downtown Anchorage were damaged and roads were ruined when a magnitude-7.0 earthquake hit Alaska’s biggest city today.

The U.S. Geological Survey said the quake occurred at 8:29 a.m. Alaska time (9:29 a.m. PT) and was centered 8 miles north of Anchorage. The main quake was followed by aftershocks in the range of magnitude 4 to 5.8.

“There is major infrastructure damage across Anchorage,” the city’s police department said in an online alert. “Many homes and buildings are damaged. Many roads and bridges are closed. Stay off the roads if you don’t need to drive. Seek a safe shelter. Check on your surroundings and loved ones.”

Some people ran out of offices, while others sought shelter under their desks. Flights coming out of and going into Anchorage’s international airport were at first stopped, and then delayed. Schools and universities closed. An Associated Press reporter working in downtown Anchorage saw cracks in a two-story building after the quake.

Power outages, flooding from water main breaks, rock slides and road closures were reported — but there were no immediate reports of serious injuries.

The temblor sparked tsunami warnings for coastal areas of Alaska, including Cook Inlet and part of the Kenai Peninsula, but the alert area never extended as far south as British Columbia or Washington state. The warnings were lifted about an hour and a half after the quake.

Alaska Gov. Bill Walker issued a disaster declaration, and surveyed the damage during an aerial tour with the Alaska Army National Guard. Anchorage’s mayor, Ethan Berkowitz, issued an emergency proclamation as well.

In a tweet, President Donald Trump said the federal government would “spare no expense” in dealing with the quake’s aftermath. “You have been hit hard by a ‘big one,’ ” Trump wrote.

One of the most powerful quakes ever recorded, measuring 9.2 on the magnitude scale, hit Anchorage in 1964. That quake created tsunami waves as high as 67 feet and is said to have caused 139 deaths in Alaska, Oregon and California, mostly due to the tsunami. Because earthquake magnitude is measured on a logarithmic scale, the 1964 quake was more than 150 times bigger and nearly 2,000 times stronger (in terms of energy release) than today’s quake.

As is usual in the age of social media, many of today’s on-the-scene reports came via Twitter. Here’s a selection of the tweets:

This post has been updated as more information became available.

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