1,406 aftershocks shake Alaska
Tremors continue to rattle state since Friday
Two days after a magnitude 7.0 earthquake struck near Anchorage, Alaska is still shaking.
Since Friday's tremor, the strongest to strike The Last Frontier since a 7.9 in the remote Rat Islands in 2014, the U.S. Geological Survey has recorded 166 aftershocks of magnitude 3.0 or higher around Anchorage as of 4:50 p.m. PST Sunday, USGS geophysicist Brad Aagaard told USA TODAY. Earthquakes of 3 or higher are strong enough to be felt.
There have been hundreds of smaller disturbances: 1,406 aftershocks of at least magnitude 1.0. The aftershocks will occur less frequently as time goes on, Aagaard said. Over the next week, the USGS has predicted 84 to 610 aftershocks of magnitude 3 or higher. Aftershocks of at least 3 are more than 99 percent likely. There's an 88 percent chance of a magnitude 5 or higher, too.
An aftershock stronger or as strong as the initial one is unlikely, however. The probability for an earthquake of magnitude 7 or higher before Dec. 8 is only 3 percent, said the USGS.
The location of the earthquake – near the subduction interface at a depth of 25 miles beneath the surface – raised the threshold for what magnitudes are felt at the surface, Aagaard said. The subduction zone is the place where two lithospheric plates come together, one riding over the other, according to the USGS.
"If this had been a much shallower one, people really would be feeling a lot more aftershocks," Aagaard said. "So that is probably helping to some extent, in terms of people not feeling as many aftershocks, because they are occurring deeper." The earthquake Friday disrupted power and heavily damaged the only highway running north of Anchorage.
The magnitude 7.0 quake, maybe remarkably, did not cause widespread damage to structures or collapse buildings.
Excavation work was underway Saturday on a highway near Eklutna, Alaska, to prepare for repaving.