‘Second Shake’ Rattles Noatak, Northwest Brooks Range

Just two weeks after the strongest earthquake in the region in more than 30 years, residents of Noatak and others near the far western edge of the Brooks Range felt another series of powerful quakes over the weekend.

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Mike West is a state seismologist and director of the Alaska Earthquake Center in Fairbanks. He says the 5.5 magnitude quake that struck at 12:57 a.m. Saturday May 3 came nearly two weeks to the day after an even stronger 5.6 quake on April 18.

“There were quite a number of earthquakes all through Saturday that were part of this aftershock sequence of this second earthquake,” West said.

Saturday’s quake was just that: an earthquake, not an aftershock from the April temblor.

“That’s a little weird for us because it doesn’t fit the aftershock paradigm,” West said. “It’s as large as the original earthquake … and was followed by its own series of aftershocks.”

Those aftershocks were similarly strong, with seven rated a magnitude four or stronger. West said the two strong quakes, both followed by powerful aftershocks, are likely caused by the same geological forces.

“It’s important to think of this as a sequence,” West emphasized. “Stress was building up through the normal movement of plate tectonics, and that needed to be relieved. The earthquake on April 18th, (Saturday)’s earthquake, all the aftershocks from both of those, are all sort of part of this process.”

Like April’s quake, the Saturday event was felt about 20 miles to the south in Noatak, at the giant Red Dog zinc mine, and even in Kotzebue. Despite the power of the “second shake,” West said there’s no danger beyond frayed nerves on the horizon. Nonetheless, he said the Earthquake Center is visiting Noatak and Kotzebue this week to install seismology equipment for better observation of the activity.

“We have plans right now to install probably two seismic stations in an around the source of the earthquake,” West said Sunday. “This is driven not so much by a concern of things to come, but we just want to be prepared, and frankly, better understand why these earthquakes occurred in the first place.”

The last time the region saw seismic activity on par with these two most recent quakes was back in 1981, when West said a 5.5 quake struck in roughly the same area about the same distance from Noatak.