G015-07
Poroelastic and elastic deformation and stress changes in the seismically active Salt Lake City region

Monday, 14 December 2020: 16:24
Virtual
Xie Hu1,2, Roland Burgmann1, Liang Xue3, Yuning Fu3 and Teng Wang4, (1)University of California Berkeley, Department of Earth and Planetary Science, Berkeley, CA, United States, (2)University of Houston, Department of Civil and Environmental Engineering, Houston, TX, United States, (3)Bowling Green State University, School of Earth, Environment and Society, Bowling Green, OH, United States, (4)Peking University, School of Earth and Space Sciences, Beijing, China
Recorded Presentation
Abstract:
Water, industrial production, and fault zones may interact through stress redistribution, yet their spatiotemporal relationship remains enigmatic. The metropolitan Salt Lake City region, recently shaken by the M5.7 Magna earthquake on March 18th, 2020, hosts such a complex system with a dynamic confined aquifer, the Great Salt Lake, the world’s largest man-made excavation - the Bingham Canyon mine and its annex tailings impoundment, as well as the most hazardous seismic zone in Utah – the Wasatch Fault System. Ground deformation mapped by Sentinel-1 SAR imagery (2014-2019) 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 correlation 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 strain field. The seasonal stress changes on the adjoining faults from poroelastic volume strain are two orders of magnitude larger than those from hydrological surface loading, but both are small compared to the annual increase of tectonic loading at seismogenic depths. Historic seismic events, limited in number, do not exhibit statistically significant annual periodicity and hydrological modulation of microseismicity, and the triggering of the recent M5.7 event is not evident. Instead, we note a compelling spatial correlation between the mine tailings impoundment and one persistent earthquake cluster in recent decades, as well as the M5.7 Magna earthquake and its aftershocks. Stress changes from 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. Comprehensive seismic monitoring near sites of massive industrial production appears warranted in fragile geological and tectonic settings to ensure sustainable development.
<< Previous Abstract | Next Abstract >>