A powerful magnitude 7.0 earthquake shook the City of Anchorage, its suburbs, and points beyond this morning, causing widespread damage in Alaska’s largest city. The quake was the strongest to hit the city in more than fifty years.
Thankfully, no fatalities have been reported, and buildings throughout the region appear to be structurally intact. However, damage transportation, electric, energy, and water infrastructure appears to be rather extensive. Residents are grappling with power outages, road closures, and wrecked belongings.
It will be a long time before Anchorage has recovered from this event.
The November 30, 2018, Mw 7.0 earthquake near Anchorage, Alaska, occurred as the result of normal faulting at a depth of about 40 km.
Focal mechanism solutions for the event indicate slip occurred on a moderately dipping fault striking north-south (dipping either to the east at about 30 degrees, or the west at about 60 degrees).
At the location of this earthquake, the Pacific plate is moving towards the northwest with respect to the North America plate at about 57 mm/yr, subducting beneath Alaska at the Alaska-Aleutians Trench, approximately 150 km south-southeast of this event. The location and mechanism of this earthquake indicate rupture occurred on an intraslab fault within the subducting Pacific slab, rather than on the shallower thrust-faulting interface between these two plates.
Earthquakes are common in this region. Over the past century, 14 other M 6+ earthquakes have occurred within 150 km of the November 30, 2018 event. Two of these – a M 6.6 earthquake in July 1983 and a M 6.4 event in September 1983 – were at a similarly shallow depth and caused damage in the region of Valdez.
The M 9.2 great Alaska earthquake of March 1964, was an interface thrust faulting earthquake that ruptured over several hundred kilometers between Anchorage and the Alaska-Aleutians trench, and to the southwest.
The Glenn and Seward highways in town reopened early Friday afternoon, according to an update from Anchorage police. But detours and delays continue. Damage was a moving target, with new updates still coming in Friday evening.
There were several reports of serious road damage. The Glenn Highway had closed north of Eagle River because of damage to the southbound Eagle River bridge, and an on-ramp at the interchange of International Airport Road and Minnesota Boulevard collapsed.
A section of highway between Eklutna and Mirror Lake cracked and crumbled, closing southbound lanes for several days, according to Alaska Department of Transportation project engineer Rod Cummings. Southbound traffic will be routed around the area until crews can repair the damage.
The Palmer exit off the highway was closed after a gap appeared between the abutment and the bridge, officials said.
Vine Road near Wasilla also suffered major damage and a section is closed. From above, the heavily used connector road looked like a giant bowling ball hit it. Point MacKenzie Road sustained serious damage as well.
The City of Anchorage and the State of Alaska have each declared a state of emergency. A request for federal assistance has already been approved.