Fault Found!
From Deseret News article of January 8, 1999
One of two faults intentionally omitted from recent building maps of Salt Lake City has been officially "found." One branch of the Warm Springs Fault -- a part of the larger Wasatch Fault which was "inferred" on earlier maps by geologists -- was unearthed in recent construction at the Salt Lake City Salt Palace.
It has not been determined if the erasure of these two faults on the maps was deliberate and planned.... planned so that construction in Salt Lake City could go unrestricted and unquestioned.
The other inferred branch of the Warm Springs fault has been shown to run under the current massive construction of the LDS, Mormon Assembly Hall, under the Mormon Temple Grounds, and further south into downtown Salt Lake City.
By Jason Swensen http://deseretnews.com/staff/card/1,1228,144,00.html
Deseret News staff writer
An unwelcome reminder of the Wasatch Front's seismic past has temporarily suspended construction of the expansion of the Salt Palace Convention Center.
Geotechnical engineers recently discovered a small tectonic fault in the 25-foot-deep construction excavation site south of the Salt Palace (100 S. West Temple). The fault line is visible about halfway between West Temple and 200 West.
County officials opted Wednesday to shut down excavation and construction of the expansion for 30 days to allow further studies of the fault by the project's geologic consultants and project designers.
A second opinion on the fault has also been commissioned, Salt Lake County Commissioner Brent Overson said.
"This is a public safety matter; we want to look at all our options," Overson said.
Depending on the findings of the ongoing study, those options could range from abandoning the current Salt Palace expansion construction site to simply building around the fault.
The Salt Palace expansion was expected to be completed in July of 2000.
What is not certain is if the fault extends north into the existing Salt Palace Convention Center building. The fault was discovered under about 25 feet of fill dirt and appears to be at the surface of native soil. Geological study was not conducted that deep during the excavation of the first phase of Salt Palace construction.
Lee Allison, director of the Utah Geological Survey, said the geologic feature discovered at the expansion site may be the southern tip of the Warm Springs Fault, a branch of the Wasatch Fault.
"I think we feel pretty confident that (the fault) is under the existing Salt Palace and continues north," Allison said.
Geologist David Simon, the consultant who discovered the fault, said the geological studies of the first phase were "diligent and prudent," adding the project managers did all they could to identify any geologic problems.
The current Salt Palace building was de- signed to seismic zone 3 standards, which reportedly means it would remain standing in a Richter scale 7 earthquake.
"We upgraded the steel in the (Salt Palace) exhibit hall to accommodate what was seen in the Northridge earthquake," said Salt Palace project manager Ken Ament.
Although the existing Salt Palace is designed to withstand shaking, it is uncertain how the building would react if there was a rupture along the fault, said Allison, acknowledging that he is a geologist, not a structural engineer.
Excavation teams plan to dig trenches closer to the existing Salt Palace building to see if the fault extends that far north.
The fault is considered small because it appears displacement is only about one to three feet, Simon said.
Geologists are concerned about the fault's liquefaction features. When liquefaction occurs, soil and sand behave like dense fluid rather than a wet solid mass during an earthquake, assuming quicksand-like properties. Liquefaction occurs when soils that are granular or sandy, with a loose density, are waterlogged and are subjected to seismic activity.
A fault is considered active if it is less then 10,000 years old. Although carbon dating is needed to confirm a fault's age, Allison said preliminary evidence suggests the Salt Palace fault is active.
Allison, who applauded Salt Lake County officials for being upfront about the fault, said he would still rather be in the Salt Palace during an earthquake then many older area structures built away from a fault.
Temporarily suspending construction of the expansion project will not be costly in the short run, Overson said. The halt will cost about $300,000, less than 1 percent of the project.
Long-range costs can only be determined after gathering the findings of the ongoing study.
Ament said dealing with faults is an unavoidable aspect of construction work along the Wasatch Front, saying several Salt Lake-area buildings are built on fault lines.
The $47.5 million expansion project is expected to add about 200,000 square feet of exhibit hall, ballroom, circulation and support areas to the Salt Palace. Six hundred underground parking stalls are also planned.
The Salt Palace Convention Center, including the expansion, is expected to house the main media center during the 2002 Winter Games. If the expansion could not be built, some redesign would be needed to accommodate the thousands of journalists expected to cover the Games, said Salt Lake Organizing Committee spokeswoman Shelley Thomas.
"It would make things a little tighter, but we can make it work," Thomas said.
Article about fault being deleted from recent maps
Page Modified April 17, 1999