A majority of Salt Lake homes and buildings listed on the National Register of Historic Places, including the Capitol, would suffer damage beyond repair if a major earthquake rocked the city, said a state historical architect.
Donald C. Hartley, an architect with the division of state history, spoke Tuesday in a workshop about earthquakes and Utah historic buildings at the sixth annual Wasatch Front Earthquake Conference."In a major earthquake, there would be a high incidence of structural damage to our historic buildings . . . most of it irreparable," Hartley said.
According to structural engineer Edmund W. Allen, specific damage to the Capitol would be hard to predict.
But Allen said,"Anytime you're working with a vintage building like the Capitol, damage sustained in an earthquake would be major."
Of the 200 structures listed on the national register, Hartley said, the majority are built with unreinforced masonry, which according to experts is the weakest type of construction to withstand an earthquake.
Hartley emphasized that while the Division of State History is concerned about reinforcing the historic structures, it is more concerned with public safety.
"Although we're trying to protect Utah's cultural resources, the bottom-line issue is whether or not people are safe in those buildings," he said.
Many of the buildings on the list withstood a 1934 earthquake calculated at 6.75 on the Richter scale. Only one person was killed in that temblor, which had an epicenter 100 miles northwest of the city. But experts say if a similar quake shook the Wasatch Fault today, injuries would be worse.
Robert B. Smith, University of Utah professor of geophysics, said a 6.75 quake would crack the ground, causing "extensive damage to buildings."
"The Loma Prieta earthquake (near San Francisco) last October killed 60 people and measured 7.1 on the Richter scale, so you can figure that one of that magnitude here would result in serious injuries and some deaths," Smith said.
Some other structures on the register include the Salt Lake City/County Building - which was seismically reinforced during its renovation, Temple Square buildings, the Cathedral of the Madeleine, the Hotel Utah building, the Capitol Theatre, Hansen Planetarium, the Rio Grande and Union Pacific Railroad stations and the old Wasatch Springs Plunge building, which now houses The Children's Museum of Utah.
According to LDS Church spokesman Don LeFevre, The Assembly Hall on Temple Square was seismically upgraded as part of extensive renovation a few years ago.
Although the Tabernacle has not been seismically reinforced, LeFevre said, Church engineers say its flat, non-vertical construction makes it strong enough to survive an earthquake.
LeFevre said the Salt Lake LDS Temple does not require reinforcement because of its original thick-walled construction.
All of the buildings on Temple Square are listed in the register as National Historic Landmarks.
Allen, whose firm reinforced the City/County Building, said both the Hotel Utah building and the Cathedral of the Madeleine are undergoing design assessments to determine the need for seismic upgrading.