Engineers: SLC's Aging Buildings Not Earthquake Safe

Engineers: SLC's Aging Buildings Not Earthquake Safe

Save Story

Estimated read time: 4-5 minutes

This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.

SALT LAKE CITY (AP) -- Utah is shoring up its marble statehouse against an overdue earthquake, but legislators said they couldn't afford to fix another known deathtrap -- the busy University of Utah library, which is expected to "pancake" on itself in a quake of magnitude 5.0 or greater because of a fatal design flaw.

The debate underscores the dangers in this city, where officials say two out of every three buildings are considered dangerously unsafe even from moderate ground shaking. And geologists for years have warned this mountain basin is due for a powerful jolt, one that returns with fair regularity about every 1,300 years.

A magnitude 7.5 quake could kill 7,600 people in the Salt Lake basin, injure 44,000 others and cause $12 billion in building damage, a pair of Stanford University engineers calculated in 1994.

One leading advocate for building safety says this city's aging stock of unreinforced brick and masonry buildings looks a lot like San Francisco's before the 1906 earthquake devastated much of that city.

"I'll be very candid with you," Lawrence Reaveley says when asked to describe the earthquake hazards here. Reaveley, who is chairman of the University of Utah engineering department, goes on to describe a cascade of peeling, buckling and collapsing buildings that "will just flat-out kill you.

"The streets and sidewalks become the most dangerous place" because of falling debris, he said.

Around downtown, about 20 new or strengthened buildings stand among older buildings that are likely to fail in an earthquake. That could provide a vivid, side-by-side contrast between buildings left standing and others that could crumble, says city building inspector Larry Wiley.

Across the city and valley, about 56,000 houses are built of unreinforced masonry. With any kind of ground shaking, engineers say, their brick walls will instantly crack and could topple, bringing down roofs.

It sounds like a horror movie, but engineers, geologists and emergency officials are serious about the vulnerability of Salt Lake's aging and unreinforced buildings, a warning underscored by recent debate over the University of Utah's Marriott Library.

The library is considered so menacing the Federal Emergency Management Agency stepped up April 5 to help pay for earthquake bracing that the Utah Legislature had refused to fund only weeks before. But FEMA offered only $2.9 million and the Legislature still has to come up with the rest of the $45 million for structural repairs, which could take until next year or longer.

FEMA's contribution "adds credibility to the importance of this project," says Arthur "Parry" Brown, a partner for Reaveley Engineers & Associates. "It would be hard for the Utah Legislature to totally ignore it."

Legislators said they didn't want to go deeper into debt to pay for the library at the same time they were borrowing heavily to overhaul the Utah Capitol, which also is at risk of collapsing from a moderate temblor. The Capitol is being emptied this month for four years of work that will include lifting the 67,500-ton statehouse on a set of shock absorbers. The entire project will cost $200 million.

Earthquake-resistant buildings are supposed to stand up and stay mostly intact. But engineers don't guarantee they'll remain open for occupancy or useable after a quake.

"If we can get you out of the building without killing you, we're happy," says Reaveley.

While geologists have long known Salt Lake City was vulnerable to an ancient rhythm of immense earthquakes, they have only recently begun to understand how savagely the ground can shake when it happens.

The Wasatch fault here last slipped about 1,284 years ago -- and the intervals between each of the four most recent prehistoric quakes ranged from 1,270 to 1,442 years. For experts who determined those dates, it's as close to clockwork as geology gets.

To illustrate the dangers here, engineering consultants URS Corp. of Oakland, Calif., produced a block-by-block map of the shake hazards from a typical magnitude-7 quake originating 10 miles underground. It shows few safe zones, with most areas rated for strong or violent shaking.

On the gravelly Wasatch bench where the Capitol sits, the shaking will be more violent than on the basin floor, where unconsolidated soils could liquefy, proving that no area can be considered safe.

At the university campus, the five-story Marriott Library will "pancake" on itself in a 5.0-magnitude quake because of a design problem, says Joseph R. Harmon, the campus structural engineer.

Just an inch of building sway could cause welds holding the top floor to snap from steel columns, dropping the concrete slab onto lower floors and bringing them down one-by-one, he said.

The library routinely draws about 4,000 people each day. Those inside would have little chance of escaping during an earthquake, which would likely destroy a $300 million collection that includes rare books and photographs.

In downtown Salt Lake City, the list of earthquake-resistant buildings includes the Wallace F. Bennett Federal Building, the city's new library, the Hotel Monaco, several office towers and the Joseph Smith Memorial Building, formerly the Hotel Utah.

Another such structure is the Deseret News building, which has a three-dimensional framework of beams rigidly connected to columns that are bolted to concrete footings. The steel beams can flex and yield to enormous pressures without breaking, dissipating the energy of a quake, Brown says.

(Copyright 2004 by The Associated Press. All Rights Reserved.)

Most recent Utah stories

Related topics



Get informative articles and interesting stories delivered to your inbox weekly. Subscribe to the Trending 5.
By subscribing, you acknowledge and agree to's Terms of Use and Privacy Policy.

KSL Weather Forecast