Sunday morning's magnitude-7.1 earthquake is the strongest of its kind ever recorded in the Cook Inlet area, according to Alaska-based seismologists.
Sara Meyer, a research technician with the Alaska Earthquake Center at the University of Alaska Fairbanks Geophysical Institute, said Sunday morning an initial magnitude of 6.8 was revised upward shortly after the 1:30 a.m. temblor to the figure reported by the U.S. Geological Survey. Numerous aftershocks were still being recorded Sunday morning.
"Our official magnitude that we're reporting is 7.1, and that's in agreement with USGS and the National Tsunami Warning Center," Meyer said.
Meyer said the tectonic cause of the quake, recorded at a depth of 76 miles, was the Pacific Plate of the Earth's crust sliding beneath the North American Plate.
"This is actually the largest intermediate-depth earthquake in the Cook Inlet that we've seen since we set up equipment in the 1960s," Meyer said.
The Alaska Volcano Observatory didn't report any volcanic activity in connection with the quake Sunday, according to a message on Twitter.
Meyer said the quake happened at the same depth and at roughly the same spot as a magnitude 6.3 quake on the night of July 28, 2015. People across Southcentral Alaska who felt that quake said it was strong enough to tilt pictures on the walls without making them fall.
Sunday's quake still pales in comparison to the deadly 1964 Good Friday earthquake, a magnitude-9.2 event that caused a temblor and tsunami that leveled parts of Kodiak, Seward and Valdez.
Meyer said so far this year, Alaska seems to be experiencing an average amount of seismic activity. She said that the most unusual element of Sunday's quake wasn't so much its magnitude as its location.
"Alaska's earthquake prone so this is nothing out of the ordinary," Meyer said. "Earthquakes of this magnitude are fairly common in the Aleutians, but there's very few people out there -- when one this size happens in Southcentral, it's a fairly big deal."