Brain Food: The Active Seismic Zone of Northern Arizona

Jul 17, 2014

Earthquakes can’t be predicted, but Professor Dave Brumbaugh says Northern Arizona can expect seismic activity simply because there are a number of faults here. Brumbaugh is the director of the Arizona Earthquake Information Center on the Northern Arizona University Campus. He says the Earth’s crust in the region is expanding.

Northern Arizona University professor Dave Brumbaugh is the director of the Arizona Earthquake Information Center.
Credit Bonnie Stevens

“Basically everything from west of Flagstaff, let’s say around the Williams area over just a little bit to the east of Flagstaff is the zone that we call the Northern Arizona Seismic Belt and this activity can be traced from Blue Ridge up through Flagstaff, up through the canyon and up into Utah where it merges with the Inter Mountain Seismic Belt,” he says.

The largest fault on the southern part of the Colorado Plateau is the Anderson Mesa Fault south of Flagstaff. It’s about 20 miles long. Brumbaugh says it has the potential of producing a strong earthquake, one perhaps with a magnitude as  big as 6.9. 

A readout from the NAU center during a 5.2 magnitude June earthquake in southern Arizona.
Credit Bonnie Stevens

“That would mean a tremendous amount of damage in Flagstaff. We’re talking about roads disrupted, waterlines out, maybe disruption of power, such as electricity, some building collapse, injuries, possible deaths,” he says.

Although he can’t say when or even if such a quake would occur, Brumbaugh says often there are swarms of seismic activity — small tremors — leading up to a significant events. The last seismic swarm in Northern Arizona was in 2011, more than 25 miles underground.