An active seismic fault runs along the western edge of the Wasatch Mountains.
“Basically, running from South Central Utah all the way up to southern Idaho. … And different segments of this fault have experienced earthquakes in the past — from my understanding, the Wasatch is capable of producing something like magnitude seven-plus earthquakes,” said Shrisharan Shreedharan, an assistant professor of geosciences at Utah State University and the lead author on a recent study of earthquake mechanics at the Wasatch Fault.
“So earthquakes happen because of, in the simplest sense, two pieces of rock rubbing past each other. And earthquakes in nature are incredibly complicated, right? Like, there's a lot of different parameters that together influence the behavior of an earthquake. Like, was it fast? Was it slow? Was it shallow? Was it deep?” Shreedharan said.
When scientists forecast earthquake risk, they consider numerous variables, including the slope of the fault and the friction of the rocks. A steeper slope is more likely to slip, as is one with less friction.
Historic seismic activity suggests slip occurs on the Wasatch Fault even in areas with shallow slopes. Shreedharan and his colleagues compared rocks from the Brigham City segment of the Wasatch Fault Zone with rocks from outside the fault to examine the frictional properties of the rocks.
“We found that the rock that had experienced previous damage from past historic earthquakes on the Wasatch over tens of thousands of years was weaker, frictionally weaker than a rock that was further away from the damage zone,” Shreedharan said.
Shreedharan said understanding how faults slip and the properties of specific faults that may contribute to their seismic potential will help forecasters more accurately predict earthquake danger.
“This work was funded by the US Geological Survey Earthquake Hazards Program. And I just want to point out that stuff like this will not be possible in the future, if programs like this go away,” Shreedharan said.
