Sept. 27, 1999
Geologists studying a fault on the doorstep of a chemical weapons incinerator in Tooele County say that fault has as great an earthquake-producing potential as the famous Wasatch Fault on the east side of the Salt Lake Valley.
In fact, the fault has produced earthquakes at least four times. Science Specialist Ed Yeates reports.
A team of geologists takes a long, hard look at the walls of these new trenches dissecting what is called the Mercur Fault on the southwest end of the Oquirrh Mountain range.
The first of three trenches is less than a mile from the incinerator.
The Mercur trench documents four separate earthquakes, all magnitude seven or greater with actual ground displacement or vertical separation at the fault of up to six or seven feet.
The incinerator plant was built to Utah's seismic zone three building code, which is currently below the seven magnitude range.
Incinerator Operations Manager Ted Ryba says, "Basically, that means that we are able to withstand a magnitude 6.5 earthquake directly at the site."
The Mercur Fault has the potential to direct a much larger earthquake under the site. But geologists with a California based Seismic Hazards Group-- who are doing the study-- say this fault, while active-- does NOT move as often as the Wasatch Fault.
Ted Ryba says the plant is built strong enough most likely to withstand a lot of ground shaking above magnitude 6.5.
Both Ryba and Col. Ed Pate say this latest earthquake risk is another reason why weapons stored in bunkers at the Army Depot need to be destroyed quickly. At the current timetable, all weapons at the Depot would be destroyed by 2003.
Susan Olig with the California geological group says researchers need to analyze soil samples from the trenches before they can project the frequency of earthquakes along the Mercur Fault.
