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The Pitfalls Of Trying To Predict Utah's Next Quake

Julia Ritchey / KUER
Jim Pechmann, a seismologist at the University of Utah, points to where recent earthquakes have been recorded in the state.

Jim Pechmann is probably one of the few remaining people in the world who wears a pager clipped to his belt. But it’s for a good reason.

Pechmann is a seismologist at the University of Utah. Sometimes when that pager goes off, he knows there’s been an earthquake nearby. Like the 3.3 magnitude quake that struck near Park City just last week.

Mexico City’s devastating earthquake last week has left many Utahns wondering how the state would fare in a similar scenario. He says the first question he gets asked after a large event like the one in Mexico City is: Can that happen here, too?

“In Utah, I think what you’re talking about is the most damaging earthquake scenario for the state,” he says. “And that would be a magnitude 7 or so on the Salt Lake City segment of the Wasatch fault.”

Even so, a magnitude 7 or higher earthquake along the Wasatch Front would still cause a lot of damage, since that’s where most of the state’s population lives.


The problem is trying to figure when that might happen - something seismologists can’t yet do with precision. Pechmann says that’s because it’s complicated to try to do controlled experiments on the earth. And most fault lines only move every few decades.

“I would say there was a lot more optimism about short-period earthquake prediction in 1970s than there is right now,” he says. “Back in the 70s, there were some methods that were proposed, but on closer examination it seemed that they weren’t very reliable.”

So instead, they’ve focused on probability models called forecasts. Graham Kent, director of Nevada’s Seismological Lab, explains.

“There’s been a larger effort to do some probabilistic forecasting after an event,” he says. “So once you have an event - it might be a swarm and a magnitude 5, or it might be a magnitude 6.5 or 7 - and then what’s the likelihood of a bigger or similar-size event to hit?”

The problem, Kent says, is when these forecasts are wrong, it makes it more likely that people will ignore them in the future.

Right now, seismologists predict the Wasatch Front has a 57 percent chance of being struck by a magnitude 6 or higher sometime in the next 50 years.*

Both Kent and Pechmann say the most promising technology lies in earthquake early warning systems, which Mexico was the first to implement.


“Typically, in most cases, there’s not going to be enough time to finish your latte order at Starbucks and then get your coffee and go outside,” says Kent. “So you have to understand it’s a fleeting handful of seconds in most cases.”

Neither Utah or any other state has such a system yet. But Kent says it would give you enough time to duck under something sturdy. All of that presumes, of course, that the building you’re sitting in can take it. That’s something Nicole Nixon explores.

*This story has been modified from a previous version to correct a numerical mistake. The probability of an earthquake striking the Wasatch Front over the next 50 years is 57 percent, not 40 percent as previously written. 

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