Micromechanical Controls on Brittle to Plastic Fault Zone Deformation.

다국어 초록 (Multilingual Abstract)

This thesis focuses on the applications of experimental rock mechanics and geophysical microanalysis to the study of the structure, physical properties, and deformation mechanisms of geologic fault zones. The motivation for this approach is to connect mechanical and microstructural (micromechanical) data to physical processes occurring on faults in-situ. I examine these relationships in three distinct geologic settings, emphasizing the general interdependence of microstructure, mechanics, and mineralogy. Section 1 (Chapters 1-3) examines the physical properties on and around faults during hydrocarbon production from shale reservoirs. Chapters 1 and 2 focus on the compositional and thermal controls on shale frictional strength and stability, which provide insights into the occurrence of induced fault slip during hydraulic stimulation. Chapter 3 presents multi-scale investigations of shale matrix microstructure, employing electron microscopy and micro-computed tomography to highlight variations in pore networks with composition and reservoir setting. Section 2 (Chapter 4) explores the mechanical behavior of fault gouge from San Andreas Fault Observatory at Depth (SAFOD), which motivates a constitutive law consistent with microstructural evidence of aseismic deformation along the San Andreas Fault creeping section. Section 3 (Chapter 5) presents rheological and textural investigations of peridotite mylonite samples dredged from an oceanic transform fault, which provide new evidence of the depth extent of fluid infiltration and brittle deformation in the mantle lithosphere. Although these sections focus on distinct geophysical applications, they are united in demonstrating the utility of micromechanical studies in furthering our understanding of physical processes in geologic fault zones.