Abstract
AbstractThe interconnection between anthropogenic and natural surface loads and seismicity continues to be poorly understood. The metropolitan Salt Lake City in Utah hosts various industrial, hydrological, and tectonic processes, including the Bingham Canyon mine and its associated tailings facility, precipitation and water storage at the surface and in aquifers, as well as the seismically active Wasatch Fault Zone. The March 18, 2020 M5.7 Magna earthquake occurred east of a mine tailings impoundment that receives ∼60 million tons/yr of ore waste products since the early 1900s. Here we investigate the spatiotemporal elastic stress changes due to anthropogenic mass transfer and natural hydrological loading and unloading. Two local earthquake clusters host persistent microseismicity and the 2020 M5.7 Magna earthquake sequence. The amplitude and sign of the computed Coulomb stress changes at seismogenic depths strongly vary with the receiver fault geometry, the frictional coefficient, and the location, and can reach tens of kPa and ∼1 kPa/yr due to the tailings loads, a substantial fraction of background tectonic loading. The long‐term and seasonal stress changes from regional hydrological processes are only up to a few kPa. A lack of statistically significant seasonality in seismicity across Utah suggests a weak control by cyclic hydrological loads. Explicit knowledge of the fault architecture is essential to allow for seismic hazard assessment considering external stress loading.
Highlights
The complex nature of earthquakes and other geohazards has taught us that failure mechanisms in the crust rarely occur in isolation
Salt Lake City (SLC) and the nearby Great Salt Lake are located in the hanging wall of the Wasatch Fault Zone (WFZ), forming the eastern margin of the Basin and Range province (Fig. 1)
To compare the Coulomb stress changes Δσc due to different long-term loading sources, we first focus on a ~45-km-long EW cross section (e.g., Figs. 3a-f)
Summary
The complex nature of earthquakes and other geohazards has taught us that failure mechanisms in the crust rarely occur in isolation. Artificial load changes from landfills, construction, or quarrying may induce dynamic failures (e.g., Qian et al, 2019; Ampuero et al, 2020), yet have been largely neglected due to their small dimensions and shallow locations. Salt Lake City (SLC) and the nearby Great Salt Lake are located in the hanging wall of the Wasatch Fault Zone (WFZ), forming the eastern margin of the Basin and Range province (Fig. 1). The basin hosts the east-dipping West Valley Fault Zone (WVFZ) to the west of the Jordan River, and subparallel to the WFZ, constituting a graben that hosts a dynamic confined aquifer (Hu et al, 2018; Hu & Bürgmann, 2020).
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