2013 Annual Meeting
Salt Lake City, Utah
Field Trip Information
One field trip will take place on Saturday, 20 April 2013. (the day following the close of the regular meeting program). Departure and return times are approximate.
Sleeping Giant: The Earthquake Threat Facing Utah’s Wasatch Front
Leaders: Bill Lund and Chris duRoss, Utah Geological Survey
Download/View: Field Trip Guide [PDF; 21 pgs. ; 7.9 MB]
The Wasatch Front in northern Utah is home to the striking Wasatch Range, numerous cities and communities that house about 80% of Utah’s population, and the most continuous, active normal fault in the conterminous United States — the Wasatch fault. Although no large earthquakes have ruptured the Wasatch fault historically, the fault has a well-documented history of numerous surface-faulting earthquakes in the recent geologic past.
On this trip, we will visit prominent fault scarps on the Salt Lake City segment of the Wasatch fault, review the Holocene surface-faulting history of the fault, and discuss important issues, such as the potential for partial- and multiple-segment ruptures. We will also consider the fault in the context of Pleistocene Lake Bonneville, whose well-defined shorelines and expansive delta deposits help constrain the timing of fault movement. At Little Cottonwood Canyon near the south end of the Salt Lake City segment, we will visit classic normal-slip fault scarps displacing glacial deposits that were first recognized and described by G.K. Gilbert in 1877, causing him to issue Utah’s first earthquake-hazard warning. In the Avenues neighborhood near the University of Utah, we will visit the site of a recent urban paleoseismic investigation on the Salt Lake City segment, present an updated earthquake chronology for the segment, and consider the seismogenic relation between the Wasatch fault and the antithetic West Valley fault zone about 10 kilometers to the west in the Salt Lake Valley.
The second half of the field trip will focus on earthquake monitoring and research, and risk-reduction measures that have been applied in Utah. At the University of Utah Seismograph Stations, we will discuss the regional seismograph network and historical earthquake catalog, the threat of both moderate and large earthquakes, and ongoing seismological research. Following lunch, we will tour the seismic retrofit of the Utah State Capitol building. On the Capitol tour, we will discuss expected ground motions at the site, the details of the base-isolation seismic design, and Utah’s approach to earthquake education and outreach. Next, we will visit the Warm Springs fault, a trace of the Wasatch fault that enters downtown Salt Lake City and is the controlling geologic structure for the Capitol retrofit. Finally, we will tour the seismic retrofit of the Salt Lake City-County building, one of Utah’s finest historic buildings, and discuss the consequences of a Salt Lake City segment earthquake on the large number of unreinforced masonry buildings in the Salt Lake Valley.
Plans are to leave the Radisson at 8:00 am sharp and return around 5:30 pm on Saturday. This full-day trip includes lunch. There is a small amount of walking and some time outdoors, but it is a very non-strenuous field trip.
NOTE: Clothing Requirements
We plan to tour the new Salt Lake City Public Safety Building, which is currently under construction, to see the seismic-safety design features being incorporated into a state-of-the-art building. However, because the building is still under construction, tour participants are required to have hard hats, safety vests, safety glasses, long pants, and boots. Hard hats, vests, and glasses will be provided for you, but to attend the tour, you will need to have long pants and boots (they do not have to be steel toed, but do need to cover your ankle). Also, April weather in northern Utah can be very unpredictable - hope for the best, but come prepared for cool or wet conditions.
100% refund if cancellation is received before the online registration deadline. Field trip cancellations received after the deadline will received 100% refund IF another person fills the vacated place on the trip. Unfilled cancellations will be refunded only as funds allow.
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