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Boise State geosciences team monitors earthquake aftershocks

Technician installing a siesmometer.
Thomas Otheim, a Boise State geosciences technician, installs a seismometer near Grandjean. Photo provided by Lee Liberty.

On March 31, a  magnitude 6.5 earthquake struck about 70 miles northeast of Boise in the Challis National Forest. That event – which happened some six miles underground – rattled households across Idaho and created a rare opportunity for Boise State researchers.

A team from the geosciences department, including faculty members Lee Liberty, Dylan Mikesell, Jeffrey Johnson, Jake Anderson and technician Thomas Otheim, are installing telemetered seismometers across the region. The seismometers will provide real-time information about the location, depth and magnitude of aftershocks.

The Boise State team is partnering with the United States Geological Survey, the Idaho Geological Survey and the University of Utah on the project.

“The University of Utah seismic lab is dealing with their own earthquake from last month and they sent us some USGS equipment that they had borrowed,” said Liberty. “The University of Utah also has a strong record of responding to Idaho earthquakes, so they have been very supportive. We are discussing our progress and directly working with Idaho Geological Survey director Claudio Berti and hazards specialist Zach Lifton.”

Liberty told us more about the work.

Q. Why is it important to deploy aftershock monitoring equipment?

A. Because these types of earthquakes only happen every 10-plus years, we have little information on how the faults move, whether the load stresses on other faults, etc. The aftershock sequences provide valuable information as to what happens in the earth’s crust.

Q. How rare are earthquakes in Idaho?

A. In Idaho, we expect earthquakes with a magnitude of 5 or more every few years, for example, M5.3 earthquake in Soda Springs in 2017. We expect earthquakes with a magnitude of 6 or greater every decade or two, and a magnitude of 7 or greater every hundred years. The last big ones were near Borah Peak in 1983 (M6.9) and Hebgen Lake (M7.2) in 1959 (technically in Montana).

Q. So, we’ll experience more earthquakes in our lifetime… 

A. The probability is 100 percent that we will experience earthquakes in the coming hours, days, weeks and years. The question is where and how large. We are currently seeing M2 earthquakes each hour, M3 earthquakes a few times per day and an occasional M4. Related or not, earthquakes should be considered a naturally occurring phenomenon. We do not anticipate a damaging earthquake directly related to this earthquake series, but we should be prepared.

Q. Was there anything particularly notable about the March 31 quake?

A. This earthquake initiated on a fault that was not mapped as late Quaternary active. Meaning, it showed no previous evidence for motion in the past few hundred thousand years. But, it is likely related to a Holocene-active fault (motion in the past 10,000 years). In fact, aftershocks are lining up with this known active fault.

Q. For you, what has been the most fascinating earthquake in history, and why?

A. I have been working on the 1964 M9 Great Alaska earthquake for about a decade. It was the first studied subduction zone earthquake and we are continuing to learn a lot about this fault system and history. I have led five oceanographic surveys related to this earthquake.

Q. Is there anything else you’d like people to know?

A. Stay safe, be prepared:

More on quakes

Read about historical earthquakes in Idaho on the Idaho Geological Survey site.

Quakes for context

The strongest recorded earthquake was in 1960 in Chile. The USGS assigned this quake a magnitude of 9.5.

The San Francisco earthquake of 1906 happened before the development of the Richter magnitude scale (1935). The most widely accepted estimate for the magnitude of the quake is 7.9

The Haitian quake in 2010 had a magnitude of 7.