The seismic storm in the far western arm of the Brooks Range that began nearly two months ago continued early Monday morning.
The quake was located about 13 miles northeast of Noatak, at a depth of 15 miles.
A magnitude 4.2 shock preceded this morning’s larger quake by just one minute. The earthquake center said in online posting that it’s expecting numerous aftershocks with magnitudes up to four in the coming days.
The early-morning quake is the fifth such powerful shake since the earthquake swarm began April 18, with with two 5.7 magnitude earthquakes. Three more 5.7 temblors struck in early May and early June. In all, the larger quakes have been followed by more than 300 smaller aftershocks.
In May seismologists with the Earthquake Center installed field equipment in Noatak and Kotzebue to better monitor the activity.
Michael West, a seismologist and director of the Alaska Earthquake, said in early June that despite the new equipment, seismologists still don’t know what’s causing the powerful quake series. West said such earthquake swarms are usually seen near volcanoes, but with no volcanic activity in the region, there’s still no firm scientific consensus for what faults are causing earthquakes and other tectonic activity in that region of western Alaska.