Earthquake study looks at how ground could move under Salt Lake City

Oct 26, 2021, 6:12 PM

FILE: Caution tape surrounds the VFW building on Magna’s Main Street on Tuesday, March 24, 2020, following a 5.7 magnitude earthquake that was centered near the city on March 18. (Steve Griffin, Deseret News)

(Steve Griffin, Deseret News)

BY MARY RICHARDS

Former Reporter

SALT LAKE CITY — Live in Utah long enough, and you’ll hear somebody talking about the big earthquake that people have been expecting to hit, literally, for generations. For a state that boasts 200 active faults, the expectation isn’t unwarranted.

Today researchers from the Utah Geological Survey and from Boise State University are trying to understand more about the faults that run directly under Salt Lake City, the state’s capital city. And their newly published research paper has new information about the type of damage that Salt Lake City residents and businesses can expect.

Findings from the earthquake study

The first finding is that secondary faults may connect two faults in Salt Lake City, the East Bench and the Warm Springs fault.

The second finding involves “lateral spread deposits” in the downtown Salt Lake City area.

“Those (lateral spread deposits) are a result of earthquake ground shaking and liquefaction,” said Adam McKean, a senior geologist for the Utah Geological Survey at the Utah Division of Natural Resources.

“Liquefaction is where the water that’s in the soil moves in an earthquake. It shakes it. It vibrates it.”

The US Geological Survey defines liquefaction as taking place “when loosely packed, water-logged sediments at or near the ground surface lose their strength in response to strong ground shaking” and that “liquefaction occurring beneath buildings and other structures can cause major damage during earthquakes.”

The findings suggest earthquakes 5.0 and larger could cause ground displacement and liquefaction in Salt Lake City and that increases the risk of buildings getting damaged.

The takeaway from the earthquake study

McKean says knowing about the existence of these deposits can help businesses and residents of Salt Lake City be better prepared.

“Seeing that previous earthquakes have faulted in the surface and subsurface of the downtown area before helps us know what to prepare for, what else needs to be studied, and how these faults have functioned mechanically in the past.”

The findings from their research are published in the open-access journal The Seismic Record.

Contributing: Simone Seikaly