Older SLC buildings and homes at risk of major earthquake damage, experts say

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Structural damage to a historical brick house in Salt Lake City caused by the 2020 M5.7 Magna Earthquake. The home was subsequently demolished due to the extensive damage. (Courtesy of Earthquakes.Utah.Gov)

SALT LAKE CITY (ABC4) – During a video shared during the most recent session of General Conference, Russell M. Nelson provided a glimpse of the extensive renovation being done on the Salt Lake Temple.

“I am totally in awe when I consider that they built this magnificent temple with only tools and techniques available to them more than a century ago,” Nelson stated while standing literally inside the foundation of the building completed in 1893.

Nelson continued by suggesting that the passage of time has had a bit of a predictable result for the foundation of a building built almost entirely by hand in the pioneer days.

“These many decades later, however, if we examine the foundation closely, we can see the effects of erosion, gaps in the original stonework, and varying stages of stability in the masonry.”

As such, the temple has been closed since 2019, with the objective of retrofitting the building to be able to withstand “The Big One,” or the possibility of a magnitude 7.3 earthquake that scientists believe the Salt Lake Valley may be overdue for.

While work is being done to preserve the downtown temple, arguably the most iconic building in Utah, many other older structures in the valley could be in trouble in the event of a major earthquake due to their foundations upon unreinforced masonry.

Leon Berrett, a former chair and current member of the Utah Seismic Safety Commission, estimates that there are around 150,000 vulnerable buildings throughout the state, with 50,000 or so in the Salt Lake Valley metro area.

“There’s a lot,” he states. “And a lot of those are just residential homes or single-family dwellings, they’re not all high profile. We know the majority are not the highest-profile ones like the temple, but there certainly are a number of other unreinforced apartments, buildings, and larger buildings downtown that are of concern.”

The magnitude 5.7 earthquake that rocked Northern Utah near Magna in March 2020 served as a reminder of how susceptive Salt Lake City buildings are to earthquake-related damage. Berrett recalls as part of his surveying after the shake, he noticed more substantial damage to distant Salt Lake City buildings, due to the difference in construction materials.

“Salt Lake City has a lot of unreinforced masonry buildings, whereas in Magna, they have older homes, just like Salt Lake City does, but they’re wood constructed,” he explains. “So they just hold up better than unreinforced masonry buildings.”

Knowing this, Salt Lake City leaders have provided a program for residents to receive funding to pay for seismic retrofits to their homes or commercial buildings, called Fix the Bricks. It’s a good idea for home or building owners who have a structure built before 1975 to look into the program or a possible retrofit. While getting a retrofit can be a costly project, both in time and dollars spent, in the long run, it’s worth it.

A 2015 report developed by the Utah Chapter of the Earthquake Engineering Research Institute on behalf of the state’s Seismic Safety Commission, estimated that a magnitude 7.0 earthquake could cause $33 billion in damages, displace more than 84,000 households, and depending on the time of day, kill 2,500 residents with 9,300 needing medical assistance.

Making the investment now on preparing for a potential or even looming disaster could divert millions or billions in damages, and save many, many lives. Berrett says he has heard that that the cost savings ratio could be as high as 1 to 7, with $1 million spent on preventative measures saving $7 million in damages.

“You do get pushback from people saying, ‘Oh yeah, but what are the chances or odds of a huge earthquake coming?’ Well, they’re not zero. And they’re not 100%. But there’s someplace in the middle,” Berrett cautions.

Even if “The Big One” is still 50 years away, and Barrett says some experts have suggested that a major earthquake has a 43% probability of striking within that timeline. Making the investment now could save residents’ children or grandchildren.

Ignoring the possibility of a major earthquake isn’t a wise decision in his mind.

“If you were to get in a car and somebody said, ‘Well, you have a 1 in 10 chance of being an accident or because of how the road is right now, you probably say ‘I think I’m going to take a different route,’” he states metaphorically. “Because even if it’s not a huge chance, you think if we do different things, then we’re going to reduce the risk a lot.”

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