In the first comprehensive study of its kind for Utah, Earthquake Probabilities for the Wasatch Front Region in Utah, Idaho and Wyoming forecasts the chances for damaging earthquakes in the Wasatch Front region. In the next 50 years, there is a 43 percent chance, or nearly 1-out-of-2 odds, of at least one large earthquake of magnitude 6.75 or greater.
For a moderate quake of magnitude 5 or greater, the probability is 93 percent, or greater than 9-out-of-10 odds.
“Considering that the average age of Utah’s citizens is the youngest in the nation at about 29 years, there is a realistic chance that many current residents will experience a large earthquake in their lifetime,” says Ivan Wong, Principal Seismologist at Lettis Consultants International and lead author of the report.
The soon-to-be-released report is a collaboration of 14 scientists from academia, federal and state agencies, and private industry. The results underscore the importance of being prepared for damaging earthquakes in Utah.
Scientists cannot predict exactly when and where an earthquake will occur, and thus rely on forecasts to convey the chances of future quakes. Similar to weather forecasts, earthquake forecasts give the probability that an earthquake of a specific magnitude will occur within a specific region within a particular time period.
The new report forecasts quakes within the Wasatch Front region, where nearly 80 percent of Utah’s population resides. The report covers time periods significant to an individual’s lifetime of 30, 50 and 100 years, and addresses earthquakes strong enough to potentially cause significant to catastrophic damage, magnitude 5 up to about 7.5.
Even a moderate quake of magnitude 5 can cause considerable damage, such as fallen plaster and broken chimneys, but a large quake of magnitude 6.75 or greater can cause catastrophic damage, including collapse, to structures such as unreinforced brick buildings.
The well-known Wasatch Fault is the most likely fault in the region to generate a large earthquake, having an 18 percent probability of at least one earthquake of magnitude 6.75 or greater in the next 50 years.
However, the new report highlights many other mapped and even unmapped faults that contribute to the chances of an earthquake. When considered together, these many faults significantly increase the regional probabilities of an earthquake.
Utah residents have several resources available to help them with earthquake preparedness. The annual Great Utah Shakeout is Utah’s largest earthquake drill. Nearly 1 million people were expected to participate in this year’s drill on April 21. For more information, visit shakeout.org/utah.
Be Ready Utah, the state’s emergency preparedness program run by the Division of Emergency Management, shares information about earthquakes and other hazards on its website, BeReadyUtah.gov, and on social media.