All flights were halted at the airport after the quake knocked out telephones and forced the evacuation of the control tower, and 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. Officials opened an Anchorage convention center as an emergency shelter.
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. According to the U.S. Geological Survey, the Pacific plate is sliding northwestward and plunges beneath the North American plate in southern Alaska, the Alaska Peninsula and the Aleutian Islands.
Alaska has been hit by a number of powerful quakes over 7.0 magnitude in recent decades, including a 7.9 that hit last January southeast of Kodiak Island. But it is rare for a quake this big to strike so close such a heavily populated area.
On March 27, 1964, Alaska was hit by a magnitude 9.2 earthquake, the strongest recorded in U.S. history, centered about 75 miles (120 kilometers) east of Anchorage. The quake, which lasted about 4½ minutes, and the tsunami it triggered claimed about 130 lives.