SALT LAKE CITY — If an earthquake were to strike the Wasatch Front, it could kill as many as 2,300 and injure more than 30,000, officials say, but much of this could be prevented if Utahns retrofitted their homes for seismic safety.
The last earthquake of magnitude 5.5 or higher in Salt Lake City was in 1910, and Barry Welliver, a structural engineer, said he feels like "chicken little" warning people the sky is falling when he talks about the possibility of earthquakes in the state.
"We're playing catch up a little bit here," he said. "We're still in the denial stage."
According to the handbook for earthquakes in Utah, "Putting Down Roots in Earthquake Country," large, damaging earthquakes are most likely to occur in an area that follows the path of I-15, and "the next large earthquake is becoming increasingly likely on certain parts of the Wasatch fault," which runs through some of Salt Lake City's priciest real estate.
The homes with the greatest risk of structural safety during an earthquake include homes built before 1970, multi-storied homes, and homes with basements, stacked rock or brick foundations, or unreinforced masonry bearing walls, the handbook states.
"If your building was built before 1970, you have reason for concern," Welliver said.
There are a number of improvements, however, that homeowners can make on their home ranging from a few hundred dollars to thousands of dollars that can make them safer.
The east bench of Salt Lake City has the highest probability of destruction, with 70 percent to 100 percent of the area likely to be destroyed, according to a mayor's Office of Emergency Management map of damage estimates for a magnitude 7.0 earthquake. Other parts of the city have a 30 percent to 70 percent chance of destruction, the map based on FEMA predictions shows.
Looking at a 99-year-old home in the east bench, Welliver looked at a chimney and said that should be a homeowner's first priority.
"If you don't use it, take it down," he said.
Welliver noted chimneys, which can weigh about 3,000 pounds, can be dangerous in an earthquake. Following the 1994 Northridge earthquake in Southern California, "every chimney on every home came off," he said. Homeowners can bolt their chimney into the roof, or secure it with a steel brace.
Homeowners should take an incremental approach to retrofitting their home, Welliver added, something FEMA suggested.
"Do it when you have a planned project."
After securing or removing the chimney, the second priority should be attaching the roof to the wall, Welliver said.
Don Hartley, an architect who works in historic preservation for Utah State History, recently made seismic upgrades on his 96-year-old brick home. When his house needed a new roof, the shingles were ripped off, and metal ties and anchors were attached from the brick wall to a 2-foot by 8-foot attached to the rafters. When he remodeled his basement, he used steel straps to tie the floor joist to the concrete foundation.
"That stuff is pretty inexpensive," he said of the materials he used in his basement.
"Will it survive the big one?" he asked. "I'm not sure, but I know there are a lot of numbers between zero and seven on a Richter scale."
Hartley said Utah has a rich architectural heritage, but he's aware of the weaknesses of many buildings.
"We had a great tradition of brick masonry, but (the builders) didn't have any knowledge of the seismic threat," he said.
But today, more homeowners seem to be responding to advice to earthquake proof their property.
Michael Mahaffey, president of Home Tech Inc., said he's noticed an increase in people getting their homes retrofitted.
"More and more people have come to the realization that unreinforced masonry brick homes are stacks of bricks," he said, and in the event of an earthquake, "all those homes that are stacks of bricks will be piles of bricks."
Mahaffey said it's hard to estimate the cost to retrofit a home because all homes are different and there are a number of improvements that can be made. He said it's not uncommon for homeowners to spend $25,000 to $30,000.
"Everything that could be done to stabilize the house for a few moments is preferable," he said.
Homeowners can visit the Utah Seismic Safety Commission website to download more information about the threats of earthquakes along the Wastach Front and how to prepare for them. Those living in unreinforced masonry buildings are urged to speak with contractors and other professionals who can access what seismic upgrades need to be made to a structure.