A Broad, Distributed Active Fault Zone Lies beneath Salt Lake City, Utah

• DOI: 10.1785/0320210009
• Publication Date: 2021-06-03T22:46:53Z
• Authors: Lee M. Liberty; James St. Clair; Adam P. McKean
• Keywords: QE1-996.5; CGISS; 550; Cenozoic; elastic waves; body waves; faults; Geology; 01 natural sciences; folds; Earth Sciences; Geophysics and Seismology; earthquakes; 0105 earth and related environmental sciences

Abstract Although the Wasatch fault is currently known to have a high-seismic hazard from motion along range-bounding faults, new seismic data reveal faulted and folded 13,000–30,000-yr-old Lake Bonneville strata beneath Salt Lake City (SLC). Coupled with previous excavation trench, borehole, and other geologic and geophysical observations, we conclude that a zone of latest Pleistocene and/or Holocene faulting and folding kinematically links the East Bench and Warm Springs faults through a 3 km wide relay structure and transfer zone. We characterize faults beneath downtown SLC as active, and these faults may displace or deform the ground surface during an earthquake. Through offset but linked faults, our observations support throughgoing ruptures across faults of the Wasatch fault zone (WFZ) and an elevated risk of earthquake-induced building damage.