There’s a roughly 50% chance that a magnitude 6 or larger earthquake will shake the Wasatch Front in the next half century. And many older structures would not withstand it.
The Church of Jesus Christ of Latter-day Saints shut its historic Salt Lake City Temple on Sunday to begin four years of seismic retrofitting. It’s installing a base isolation system, like the one at the Utah State Capitol that holds up the building’s foundation.
Several base isolators are visible through a window in the Capitol basement.
“It looks like a big hockey puck,” said Bob Carey, the Utah Division of Emergency Management’s earthquake program manager. “The ones that we’re looking at here, I’m going to guess are about 3 feet across or so … As the dynamic motion coming from an earthquake comes through this area, the ground’s going to be moving fairly readily. These isolators are then going to dampen that motion so that the building itself doesn’t move very much at all.”
The system is far too expensive to use in retrofitting a home, Carey said, but more Utahns should be thinking about how to protect their houses and businesses from the effects of an earthquake. He’s particularly worried about unreinforced masonry homes, which were built before 1974 and don’t have reinforcing rods in the walls to hold the house together. According to Carey, there’s about 147,000 of them throughout the state.
“The roof can slide back and forth,” he said, “a lot of times you get the walls that fall out and then you start to get a partial collapse or a full collapse.”
In order to prevent that from happening, contractors can tie the roof to the walls and strap down the chimney to prevent it from tipping, among other strategies. But that can be expensive, running homeowners $15,000 to $20,000.
The federal government recently doubled its contribution to a Salt Lake City grant program though. “Fix the Bricks” just received $4 million from the Federal Emergency Management Agency. Grants to homeowners cover three quarters of the cost, if they have an unreinforced masonry home over 50 years old.
“FEMA seems to be really happy with what we’re doing,” said Fix the Bricks Program Manager Audrey Pierce. “They like the idea of people trying to mitigate what is our biggest potential for threat.”
But, even as the program expands, the waitlist is still almost 2,000 people long.