SALT LAKE CITY — Utah earthquake experts found nearly a decade ago that there's a 57% chance a 6.0 magnitude or greater earthquake will strike the heart of the Wasatch Front in the next four decades.

Despite a 5.7 magnitude earthquake that rattled the region three years ago, Utah Geological Survey director Bill Keach says the risk for an even larger earthquake only continues to climb.

"Our probabilities are higher today — today, greater than 1 in 2," he told members of the Utah Legislature's Natural Resources, Agriculture and Environment Interim Committee last Wednesday.

He said there's a "real" risk for an even stronger earthquake, which would be catastrophic to Utah's urban core. Keach points out that a 7.0 magnitude earthquake would be 20 times bigger and 89 times stronger than the 2020 event.

This means the cost of a major earthquake would rise significantly from the $70 million to $150 million in costs three years ago to something much greater. There's no telling how many more lives would be at risk, too.

This threat is why the Utah Legislature — using recommendations outlined by the Utah Seismic Safety Commission — set aside $150,000 toward a study to evaluate the feasibility of early earthquake detection last year. It can't predict earthquakes, but it can warn Utahns a few moments in advance of an impending major earthquake so they have at least a little time to take cover before buildings begin to shake.

Keach presented the committee with the results of the yearlong study compiled by multiple earthquake and emergency experts in the state, summarizing that it is possible for Utah to deploy early detection technology to warn residents. This, he said, could potentially save lives — especially for those a little ways away from an earthquake epicenter.

"Our goal is to get tens of seconds," he said. "We have a 'no alert zone,' but there's a lot of people that can get alerted. ... The answer is 'yes,' it's feasible to do this."

How does early detection work?

Early detection systems already exist in other parts of the world. One of these is ShakeAlert, which went into a public rollout in California in 2019 and has since become functional across the Pacific Coast.

Here's how it works. Every earthquake releases what are called "P" and "S" waves, which travel in different ways, according to the Seismological Facility for the Advancement of Geoscience. P waves move parallel to the epicenter of an earthquake under the Earth's surface, while the S wave moves perpendicularly at the same time, creating the shaking of the surface that people feel during an earthquake.

Early warning system technology tracks P waves because they travel faster than S waves. Once a sensor detects them, the data is sent to a processing center, which issues an alert shortly before any shaking is felt in many cases.

That said, P and S waves move simultaneously at the epicenter, which means there's no way to alert those directly above the epicenter of an earthquake, Keach explained to the committee.

Related:

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Warning times would vary depending on the location of an earthquake. For example, Salt Lake City residents would only have about 2 seconds' notice if a 7.0 magnitude earthquake occurred at the same Magna epicenter as the 2020 earthquake. However, Ogden residents would have 7 seconds and Provo residents would have 17 seconds to prepare after the warning, per a document given to the committee.

Yet any warning time, while short, can be important for many reasons. Researchers sent out a questionnaire to a small group of residents across wide-ranging industries, who said warnings could allow time for people to seek protection and safety, allow time for auto-shutoff of "critical lifeline systems" and also allow jails and prisons to go into lockdowns before the shaking begins.

About 9 out of every 10 people surveyed said they believe early detection information would be valuable to have for these reasons.

What would it cost?

The report estimates that it would cost about $4.8 million in one-time costs to upgrade earthquake telemetry along the Wasatch Front, as well as close to $1 million in ongoing operation and maintenance costs associated with it.

Keach calls it a "bargain" because it's a fraction of what it took to develop the ShakeAlert system and it's a drop in the bucket compared to the cost of a major earthquake. Federal Emergency Management Agency officials estimate that a 7.0 magnitude earthquake could cost Utah $80 billion in short-term economic losses alone.

FEMA also lists Utah as having the country's fourth-highest earthquake risk behind the Pacific Coast states. Researchers recommend that Utah seek partnerships with the federal government to bring ShakeAlert to Utah and make the necessary upgrades to help it function at its best along the Wasatch Front.

The system would be expanded out into central and southwest Utah at some point too, which would cost about another $7 million, Keach said.

It's too early to know yet if the Utah Legislature will set aside the requested money. Utah's 2025 fiscal year budget will be finalized by the end of the next legislative session, which wraps up on March 1, 2024.

Rep. Gay Lynn Bennion, D-Cottonwood Heights, offered an enthusiastic endorsement at the end of the presentation, noting that a University of Utah Kem C. Gardner Policy Institute report released two days before the meeting suggested that Utah should invest more than the already "historical levels" directed to future needs.

Utah lawmakers have already put money toward other improvements the Utah Seismic Safety Commission recommended in 2022. In addition to the feasibility study, $50 million was directed toward some of the seismic improvements for water aqueducts along the Wasatch Front, the top concern the commission listed at the time.

The Legislature also awarded Utah State University $2.5 million earlier this year to help it launch its new Earthquake Engineering Center, which aims to help the state plan for earthquake resiliency rapid recovery whenever "the big one" strikes.

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