ANCHORAGE, Alaska — Back-to-back earthquakes measuring 7.0 and 5.7 shattered highways and rocked buildings Friday morning in Anchorage, sending people running into the streets and briefly triggering a warning to residents in Kodiak to flee to higher ground for fear of a tsunami.

The warning was lifted without incident a short time later. There were no reports of any deaths or serious injuries.

The U.S. Geological Survey said the first and more powerful quake was centered about 7 miles north of Anchorage, Alaska’s largest city, with a population of 300,000. People ran from their offices or took cover under desks.

“It had my heart racing, and I felt a bit of motion sickness afterwards. I was scared!” April Pearce wrote on Instagram after being shaken at her desk in the town of Soldotna.

A large section of an off-ramp near the Anchorage airport collapsed, marooning a car on a narrow island of pavement surrounded by deep chasms in the concrete. Several cars crashed at a major intersection in Wasilla, north of Anchorage, during the shaking.

Anchorage Police Chief Justin Doll said he had been told that parts of the Glenn Highway, a scenic route that runs northeast out of the city past farms, mountains and glaciers, had “completely disappeared.”

The quake broke store windows, opened cracks in a two-story building downtown, disrupted electrical service and disabled traffic lights, snarling traffic.

It also threw a full-grown man out of his bathtub.

All flights in and out of the airport were suspended for hours after the quake knocked out telephones and forced the evacuation of the control tower.

The 800-mile Alaska oil pipeline was shut down while crews were sent to inspect it for damage.

Anchorage’s school system canceled classes and asked parents to pick up their children while it examined buildings for gas leaks or other damage.

Fifteen-year-old Sadie Blake and other members of the Homer High School wrestling team were at an Anchorage school gymnasium waiting for a tournament to start when the bleachers started rocking “like crazy” and the lights went out. People ran down the bleachers in the dark, trying to get out.

“It was a gym full of screams,” said team chaperone Ginny Grimes.

When it over, Sadie said, there was only one thing she could do: “I started crying.”

Jonathan Lettow was waiting with his 5-year-old daughter and other children for the school bus near their home in Wasilla when the quake struck. The children got on the ground while Lettow tried to keep them calm.

“It’s one of those things where in your head, you think, `OK, it’s going to stop,’ and you say that to yourself so many times in your head that finally you think, `OK, maybe this isn’t going to stop,’?” he said.

Soon after the shaking stopped, the school bus pulled up and the children boarded, but the driver stopped at a bridge and refused to go across because of deep cracks in the road, Lettow said.

Former Alaska Gov. Sarah Palin tweeted that her home was damaged: “Our family is intact — house is not. I imagine that’s the case for many, many others.”

Officials opened an Anchorage convention center as an emergency shelter. Gov. Bill Walker issued a disaster declaration.

Cereal boxes and packages of batteries littered the floor of a grocery store, and picture frames and mirrors were knocked from living room walls.

People went back inside after the first earthquake struck, but the 5.7 aftershock about five minutes later sent them running back into the streets. A series of smaller aftershocks followed.

A tsunami warning was issued along Alaska’s southern coast. Police in Kodiak, a city of 6,100 on Kodiak Island, 250 miles south of Anchorage, warned residents to evacuate to higher ground because a wave could hit within 10 minutes.

Michael Burgy, a senior technician with the National Tsunami Warning Center in Palmer, Alaska, said the warning was automatically generated based on the quake’s size and proximity to shore.

In Kenai, southwest of Anchorage, Brandon Slaton was alone at home and soaking in the bathtub when the earthquake struck. Slaton, who weighs 209 pounds, said it created a powerful back-and-forth sloshing that threw him out of the tub.

“It was anarchy,” he said. “There’s no pictures left on the walls, there’s no power, there’s no fish tank left. Everything that’s not tied down is broke.”