The Salt Lake segment of the Wasatch fault zone has produced eight large earthquakes in the last 12,000 years. As a whole, this network of faults generates a biggie every 900 to 1,300 years.
According to the geological record, the last temblor that exceeded magnitude 6.5, or the kind that can turn unreinforced masonry homes into piles of rubble, ripped Salt Lake 1,400 years ago.
"We're due. Enough energy has accumulated on the Salt Lake segment that a large earthquake can happen at any time," said Christopher DuRoss, of the Utah Geological Survey, who will co-lead a town hall meeting 7:30 p.m. Wednesday on Utah's seismic hazards. The event in Salt Lake City is part of the Seismological Society of America's conference and the Great Utah ShakeOut, the state's annual earthquake preparedness exercises.
Titled "Utah's Earthquakes and You It's Personal," the town hall is open to the public at the Radisson Hotel, 215 W. South Temple, where you can learn about Utah's seismic hazards and how to minimize your risks. Also Wednesday, about 500 seismologists are expected to convene at the Calvin L. Rampton Salt Palace Convention Center through Friday to share insights and the latest research into earthquakes, volcanoes and all things seismic.
Among the world's most closely studied intraplate faults, the Wasatch Fault stretches 200 miles along the western foothills of the Wellsville and Wasatch ranges from southern Idaho to Nephi. It forms the eastern structural boundary of the Great Basin, the steadily expanding region between Reno and Salt Lake City that tectonic forces are pulling apart.
Since Anglo settlement in 1850 just eight moderate quakes have occurred along the fault, but no big ones. But geological data gleaned from trenches dug by scientists show evidence of at least 22 large quakes in the last 6,000 years, according to DuRoss.
No Utah fault is this active, nor does any run under so many people. About 80 percent of the state lives along the Wasatch Front, so a big quake here could knock out major transportation and utility lines, disrupt government services and paralyze the state.
Planning is imperative and would not be possible without the information generated by the University of Utah Seismograph Stations, the Utah Geological Survey and structural engineers, according to presenter Bob Carey, who runs the earthquake program for the Utah Division of Emergency Management.
State officials run these scientists' data through a loss-estimation software called HAZUS to "give us an idea of what we have to deal with when we have one of these events," he said. "We've had these earthquakes in the past; we know we will have them in the future."
According to HAZUS, a magnitude 7 quake in Salt Lake would demolish $25 billion to $32 billion in property and claim 1,300 to 2,000 lives. A factor in this distressing scenario is the prevalence of brick as a building material along the Wasatch Front. Between 130,000 and 150,000 buildings, including many schools, are constructed from unreinforced masonry.
email@example.com Utah's earthquakes and you
The public is invited to a town hall meeting, about Utah's earthquake risk, at 7:30 p.m. Wednesday at the Radisson Hotel, 215 W. South Temple in Salt Lake City. It will feature Walter Arabasz and James Pechmann of the University of Utah, Christopher DuRoss and Bill Lund of the Utah Geological Survey, Bob Carey of the Utah Division of Emergency Management, seismic hazard experts Ivan Wong and Barry Welliver and opening remarks from Mayor Ralph Becker.