The Stress, Morphology, and Vertical Deformation of Creeping Faults
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Date
2022-10-26
Authors
Newton, Tyler
Journal Title
Journal ISSN
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Publisher
University of Oregon
Abstract
The goal of my dissertation is to broadly investigate source and surface processes on faults hosting creep and slow fault slip. The discovery of different modalities of slip has proven to be ubiquitous across faults in nearly all geologic settings, yet the geometry and physical properties of the fault surface remain difficult to constrain due to lack of physical access to faults and poorly constrained stress and vertical deformation analyses of regions hosting slow slip and creep. In this dissertation, I present an analysis of crustal stress in the Nankai Trough region of Japan constrained from seismic and aseismic slip. This work shows that slow fault slip source regions may appear to have misoriented stress fields if slow fault slip constitutes a substantial proportion of fault slip and the stress field is not well constrained by earthquakes. Further, I show that the coefficient of friction for areas hosting slow slip events is low (μ = 0.19–0.50), implying frictionally weak materials in the slow slip event source region. Next, I present an analysis of microseismicity and fault structure on the Rattlesnake Ridge landslide. This work highlights a novel approach to detect and associate microseismic events, and an analysis of microseismic events and their source frequency paired with a roughness analysis of an exposed fault scarp that hosted the recorded seismicity. This analysis explores the relationship between fault heterogeneity and source frequency, revealing that source frequency is most correlated to fault roughness at the scale of 5 cm on the Rattlesnake Ridge landslide, and the source frequency distribution remained nearly uniform throughout the duration of our experiment, suggesting a uniform fracture mechanism and elastic decoupling along the landslide body. Finally, I present an analysis of vertical deformation along coastal Washington that is predominantly driven by the Cascadia subduction zone. In this analysis of vertical land motion, I utilize data from global navigation satellite systems, leveling of geodetic monuments, tide gauge records, and a tectonic model of the Cascadia subduction zone to constrain absolute rates of vertical land movement in coastal Washington. Through this work, I generated a model of absolute vertical land movement that was combined with sea level rise estimates to inform local relative sea level projections on a community scale.
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Keywords
Event association, Event detection, Machine learning, Seismology, Stress analysis, Vertical deformation