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SALT LAKE CITY — Earthquake experts say the 4.17 magnitude aftershock felt on Tuesday evening was not necessarily expected, but isn’t unusual, either.
"The earth is getting back to some quote-unquote equilibrium," said Jamie Farrell, professor of seismology at the University of Utah.
That means that Utahns in Salt Lake, Tooele and Davis counties may feel another series of aftershocks following Tuesday night’s earthquake, Farrell said.
By Wednesday morning, the University of Utah Seismograph Stations had located 10-15 more aftershocks since Tuesday evening, he added. All of those were very small and probably not strong enough to be noticed, though.
When a fault ruptures and causes an earthquake, it changes the stress area and causes something new that wasn’t there before, according to Farrell. As a result, the earth needs to settle in order to relieve that stress and get back to a state of equilibrium.
That stress relief comes in the form of aftershocks.
Tuesday evening’s quake is considered part of the series of aftershocks following the original 5.7 magnitude earthquake that struck near Magna on March 18.
Experts know that it is part of the same sequence because it’s located in the same area, on the same fault, and happened less than a month after the original earthquake, Ferrell said.
Had it been stronger than 5.7, it would have been considered a new sequence instead of an aftershock, Farrell said. If that had been the case, the March 18 earthquake would have been considered a foreshock.
4.17 magnitude aftershock shakes Wasatch Front weeks after 5.7 Utah earthquake
A magnitude 4.17 earthquake centered near Magna shook the Wasatch Front on Tuesday night, according to the U.S. Geological Survey.It’s likely to feel aftershocks for days, weeks or months after an initial earthquake. Depending on the size of the quake, some aftershocks can even be felt for years after that first earthquake, according to Farrell.
It’s not something people should be alarmed about, he said. Earthquake experts weren’t necessarily expecting a 4.2, but it’s not unusual, either.
Though most of the aftershocks since Tuesday night haven’t been strong enough to notice, people can expect another batch of aftershocks in the next few days, especially if you’re in Magna or close to the epicenter area, Farrell said.
"Feeling more earthquakes in the next week or so would not be unexpected," he said.
Since earthquakes are unpredictable, that can lead to anxiety for people, because you don’t know when the next one might be coming, said Dr. Lucy Jones, a seismologist and founder of the Dr. Lucy Jones Center for Science & Society.
However, it can help to familiarize yourself with some of the more predictable parts of seismology, such as aftershocks being common and knowing you might feel them for days or weeks after the first one, she said.
"The aftershocks are normal, the anxiety is normal too," Jones said. "Human beings do not like uncertainty."
She encourages people to familiarize themselves with statistics and facts about earthquakes. Understanding the numbers and the patterns that earthquakes often follow can be reassuring, she said.
"Creating a new routine for this situation helps," she said.
The Great Utah Shake Out is scheduled for Thursday. The event is essentially a statewide earthquake drill that helps people be prepared for what they would do in a real earthquake.
Additionally, Be Ready Utah offers assistance for people who may be experiencing anxiety due to earthquakes or the ongoing COVID-19 pandemic.
People can call 1-800-985-5990 or text "TalkWithUs" to 66746 to be connected with a trained counselor.
For more information, visit earthquakes.utah.gov.
