Poster #124, Stress and Deformation Over Time (SDOT)

Interplay between seismicity and hydrological and industrial processes in Salt Lake Valley, Utah

Xie Hu, Roland Bürgmann, Liang Xue, Yuning Fu, & Teng Wang
Poster Image: 

Poster Presentation

2020 SCEC Annual Meeting, Poster #124, SCEC Contribution #10640 VIEW PDF
A M5.7 earthquake hit the metropolitan Salt Lake Valley (SLV) on March 18th, 2020 during the COVID-19 pandemic. The shaking certainly added more worries to ~3 million people within a 160-km radius of the capital Salt Lake City. The M5.7 earthquake was not unexpected; the Utah Geological Survey and U.S. Geological Survey’s 2016 report estimated that there is a 93% likelihood of a moderate quake of magnitude 5 or greater striking the Salt Lake City segment of the Wasatch Fault Zone in the next 50 years. In addition to the hazardous fault system, SLV also hosts a dynamic confined aquifer and the world’s largest man-made excavation - the Bingham Canyon mine and its annex tailings impoundment. De...cadal InSAR-derived ground deformation reveals an elongated area with a seasonal surface motion of ~50-mm uplift and ~30-mm extension during wintertime (reversed for summertime), corresponding to 0.03-0.06-km3 water storage cycles. The spatial association of this deforming area, hydrological discharge units and fault splays, as well as phase shifts in the displacement time series and water levels in areas separated by active faults, indicate that the faults modulate the groundwater flow and poroelastic and elastic strain field. The seasonal stress changes on the adjoining faults from volume strain are two orders of magnitude larger than those from hydrological surface/shallow loads (from the Great Salt Lake, Utah lake, aquifer, snow, and soil moisture), but the amount is small at seismogenic depths compared to the tectonic loading rate. Historic seismic events, limited in number, do not exhibit statistically significant annual periodicity and hydrological modulation of microseismicity or triggering of the recent M5.7 event is not evident. Instead, we note a compelling spatial correlation between a mine tailings impoundment and the M5.7 Magna earthquake, its aftershocks, and persistent earthquake clusters. The aggregate tailings load since the early 1900s may accelerate or decelerate the seismicity by hundreds of years depending on the location, geometry and frictional properties of active faults.