An “earthquake swarm” is hitting the Brooks Range. Seismologists do not know why it is occurring or if it will continue.

Friday night a 5.5 magnitude earthquake struck 20 miles northeast of Noatak. This is the third 5.5 quake that has struck the same area in the past two months.

Michael West is the Director of the Alaska Earthquake Information Center and said, “We are now referring to this as an ‘earthquake swarm.’ That is there’s something in the earth that is causing a whole series of earthquakes of similar size. It really is quite unusual to have this in that kind of setting.”

West said earthquake swarms are common around volcanoes. But with no volcanoes in the Brooks Range, this seismic swarm is raising questions for seismologists nationwide.

“At the moment,” West said, “we are not aware of a similar kind of sequence like this that has ever really occurred in the Brooks Range or in Western Alaska.”

West says the Earthquake Center does not know what is causing the swarm. But it does know the quakes all ruptured from the same type of fault and are all moving in the same direction.

“All of these are the same type of motion. And that certainly tells us that there is a weak zone. There is clearly a fault system that we have previously not been very aware of in this area,” West said.

Last month, technicians installed temporary seismic stations in Noatak and Kotzebue after the second major quake hit the area. West says the data will allow seismologists to “see inside the fault,” and the stations are recording hundreds of aftershocks, helping seismologists better understand what is happening beneath the Brooks Range.

No injuries or damage has been reported.