The Utah Capitol is a time bomb set to go off with a major earthquake.
In a press briefing Friday, two members of the Capitol Preservation Board discussed a study of the earthquake damage to the Washington Capitol in Olympia in a Feb. 28 temblor and concluded that in a similar situation, Utah's Capitol would not withstand the shaking and rolling ground.
"It will break itself apart," said David Hart, executive director of the Capitol Preservation Board. He was concerned particularly with the differences between the two buildings.
Washington's Capitol has strong support walls within the building, called shear walls, that absorbed most of the earthquake's force. Utah's Capitol, with its end-to-end open interior, lacks those shear walls and would not fare as well as Washington's in a quake of similar magnitude.
When contractors built the Utah Capitol from 1911 to 1917, they did not attach the outer walls to the frame, as is the custom in modern construction techniques, Hart said. So the brick facade of the building is little more than a pile of blocks, with nothing binding them.
Although Washington's Capitol was built 10 years after Utah's, the earthquake technology and equipment were very similar. The main difference now is that the building in Olympia had been partially retrofitted for earthquake reactivity, and that's what saved it, Hart said. On the other hand, Utah's Capitol has had virtually no retrofitting work completed since it was originally built.
"If that (earthquake) happened in Utah, people would have been very, very badly injured or killed," Hart said.
The February earthquake originated about 30 miles below the surface of the earth, and only about 10 or 11 miles from the Washington building. Utah's faults are much closer to the surface, which would decrease dampening, or ground absorption of seismic waves. Thus, the Utah Capitol would feel a greater vertical impact.
Utah's building also would sustain a greater horizontal impact, because the Wasatch Front has faults that stretch from Provo to Ogden. The farther away the fault, the more horizontal impact the building will sustain.
Compounding that threat is the Capitol's vantage point. Although its location makes for a great view, the peninsula known as Capitol Hill is more susceptible to horizontal movement. In an earthquake, ground movement would affect the peninsula at several points because it protrudes from the surrounding area, and that would multiply the effect of an earthquake and concentrate the waves near the Capitol. That in turn means more horizontal impact, which means more side-to-side swaying. And that possibility has Hart shaking.
The solid marble columns that support the Capitol's fourth floor are brittle and do not allow for side-to-side movement. If the columns come down, so does the fourth floor. The fourth floor would land on the third floor and so on as the building collapsed on itself.
But there is hope. In a three-year, $200 million-plus project, the Capitol Preservation Board proposes to make its home better equipped to deal with "seismic events."
As part of that project, the retrofitting crew would isolate the Capitol's base, which allows the ground to move independently from the building, minimizing infrastructure damage. Also, the crew would reinforce existing walls to make them shear, which would lend support to the building's entire frame. Finally, workers would have to reinforce the dome with a steel mesh and collars.
If all goes as planned, the retrofitting would be complete in time for the 2008 legislative session.
E-mail: kswinyard@desnews.com