STABILITY ANALYSIS OF THE ANCIENT SEVIER GRAVITY SLIDE, SOUTHWEST MARYSVALE VOLCANIC FIELD, UTAH
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Date
2020-12
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The Ohio State University
Abstract
The Sevier Gravity Slide (SGS) is a long-runout landslide, part of the Markagunt Gravity Slide Complex in the Marysvale Volcanic Field, southwest Utah. The SGS was a single catastrophic emplacement event, hypothesized to have initiated by failure of the volcanic field via gravitational stress perturbations. While initiation is agreed to be gravity driven, the regional stress state and the topography at the time of emplacement is unclear, as well as any potential triggering mechanisms. In this project, without considering triggering events, I vary far field stresses as well as the topographic surface to analyze their impacts on the subsurface stress distribution and potential for slide initiation. In the model, I idealize the problem as a single body, with an upper boundary acting as the paleo-topographic surface. The parameters of the model are the mechanical properties of the idealized rock body, the far field, tectonically driven stress field, the topographic surface and boundary conditions for that surface. I constrain the topographic surface as a free surface, maintaining zero shear and normal strength. Using the Boundary Element Method, I calculate topographically driven stress perturbations beneath the topography and superimpose those on the regional state of stress to create a full stress distribution beneath topography. Secondly, I place observation points along a potential detachment surface for the slide to calculate normal and shear stresses. With various far field stress states and topography, I analyze the effect on the shear stress along the potential detachment surface and infer which paleo-conditions are most preferential for potential detachment and initiation of the slide. The results of this model are taken to be a starting point in modeling the true initiation of the gravity slide, and potential initiation mechanism and their addition to the provided modeling framework is discussed.
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Keywords
Landslides, Long-runout landslides, Sevier Gravity Slide, Marysvale Volcanic Field, geomechanics, modeling, boundary element method