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Rate & state dependent friction and the nucleation of long runout landslides: Application to the Marysvale Gravity Slide Complex, Utah

Danika Mayback, William A. Griffith, Michael J. Braunagel, Robert F. Biek, David B. Hacker, David H. Malone, & Tiffany A. Rivera

Submitted September 11, 2022, SCEC Contribution #12535, 2022 SCEC Annual Meeting Poster #173

Subaerial long-runout landslides are among Earth’s most catastrophic natural hazards due to the volume of landslide material and transport distance; however, the factors that lead to the initiation of runaway unstable long-runout landslides are unclear. The Oligocene-Miocene Marysvale Gravity Slide Complex (MGSC) in southwestern Utah is currently the largest known subaerial long-runout landslide complex on Earth comprising three distinct gravity slides structurally defined by a breakaway zone, a bedding plane detachment surface, a ramp cutting up from the bedding plane segment to the surface, and an end runout area covering the former land surface. The MGSC is further characterized by rapid emplacement generating extensive pseudotachylytes and clastic dikes. For deep seated rockslides, initiation is governed by the frictional resistance of the detachment surface, which occurred within the clay-rich, structurally weak Brian Head Formation for the MGSC. This study aims to constrain the conditions leading to initiation of the massive (>8000 km2) landslides by understanding frictional properties of the Brian Head Formation as a function of composition and stratigraphic position at depths of 1-2km. Frictional resistance in sliding is a dynamic process governed by periods of stability and instability described as rate-and-state dependent friction. Here, steady-state friction is analyzed using a direct-shear L-block configuration in a triaxial apparatus. Direct shear friction experiments use velocity-step and slide-hold-slide events to characterize velocity effects and determine the internal state variable used in describing how the friction coefficient evolves. We present initial results on the frictional behavior of the Brian Head Formation and discuss how results will be used in scaling exercises to explain the size of each slide in the MGSC.

Key Words
Landslides, Rate and State Friction, Marysvale, Utah

Mayback, D., Griffith, W. A., Braunagel, M. J., Biek, R. F., Hacker, D. B., Malone, D. H., & Rivera, T. A. (2022, 09). Rate & state dependent friction and the nucleation of long runout landslides: Application to the Marysvale Gravity Slide Complex, Utah. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)