In re Cox\u27 Estate, 380 P.2d 584 (Mont. 1963)

In re Cox\u27 Estat

In re Cox\u27 Estate, 380 P.2d 584 (Mont. 1963)

In re Cox\u27 Estat

Lane v. Warden, Maryland Penitentiary, 320 F.2d 179 (4th Cir. 1963)

Lane v. Warden, Maryland Penitentiar

Lane v. Warden, Maryland Penitentiary, 320 F.2d 179 (4th Cir. 1963)

Lane v. Warden, Maryland Penitentiar

The impact of rheology on the transition from stick‐slip to creep in a semi‐brittle analog

Faults can release energy via a variety of different slip mechanisms ranging from steady creep to fast and destructive earthquakes. Tying the rheology of the crust to various slip dynamics is important for our understanding of plate tectonics and earthquake generation. Here, we propose that the interplay of fractures and viscous flow leads to a spectrum between stick-slip and creep. We use an elasto-visco-plastic rock analog (Carbopol U-21) where we vary the yield stress to investigate its impact on slip dynamics in shear experiments. The experiments are performed using a simple shear apparatus, which provides distributed shear across the entire width of the experiment and allows in situ observations of deformation. We record force and displacement during deformation and use time lapse photography to document fracture development. A low yield stress (25 Pa) leads to creep dynamics in the absence of fractures. An intermediate yield stress (144 Pa) leads to the development and interaction of opening (mode I) and shear (mode II) fractures. This interaction leads to a spectrum in slip dynamics ranging from creep to stick-slip. A high yield stress (357 Pa) results in the development of many mode I fractures and a deformation signal dominated by stick-slip. These results show that bulk yield stress, fracture formation, and slip dynamics are closely linked and can lead to a continuum between creep and stick-slip. We suggest that rheology should be considered as an additional mechanism to explain the broad range of slip dynamics in natural faults

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Physical Experiments of Tectonic Deformation and Processes: Building a Strong Community

The recent revolution in the analysis of physical experiments of tectonic processes has provided new quantitative tools to analyze their outcomes. Physical experiments using scaled analog models are unique in providing information on complex three-dimensional deformation where processes can be directly observed. These observations critically complement insights gained from field and analytical/numerical investigations. Recent innovations in rheologic testing, digital image processing, and data collection are revolutionizing how we use experiments to provide insight into crustal deformation. At the same time, we are seeing the benefits of physical experiments in classroom teaching by engaging students in hypothesis testing and hands-on laboratory experience. Strengthening of the community of physical experimentalists and instructors using analog materials to simulate tectonic processes will enhance our understanding of these processes, lend more power both to interpretations of field observations and to validation of numerical models, and deepen student understanding of tectonic mechanisms. A step toward a stronger community has been made with a recent workshop on physical modeling of tectonic processes, and this report is one outcome of that workshop

New ring shear deformation apparatus for three-dimensional multiphase experiments: First results

Multiphase deformation, where a solid and fluid phase deform simultaneously, play a crucial role in a variety of geological hazards, such as landslides, glacial slip, and the transition from earthquakes to slow slip. In all these examples a continuous, viscous or fluid-like phase is mixed with a granular or brittle phase where both phases deform simultaneously when stressed. Understanding the interaction between the phases and how they will impact deformation dynamics is essential to improve hazard assessments for a wide variety of geo-hazards. Here, we present the design and first experimental results from a ring shear deformation apparatus capable of deforming multiple phases simultaneously. The experimental design allows for three dimensional observations during deformation in addition to unlimited shear strain, controllable normal force, and a variety of boundary conditions. To impose shear deformation, either the experimental chamber or lid rotate around its central axis while the other remains stationary. Normal and pulling force data are collected with force gauges located on the lid of the apparatus and between the pulling motor and the experimental chamber. Experimental materials are chosen to match the light refraction index of the experimental chamber, such that 3D observations can be made throughout the experiment with the help of a laser light sheet. We present experimental results where we deform hydropolymer orbs and cubes (brittle phase) and Carbopol&reg; hydropolymer gel (fluid phase). Preliminary results show variability in force measurements and deformation styles between solid and fluid end member experiments. The ratio of solids to fluids and their relative competencies in multiphase experiments control deformation dynamics, which range from stick-slip to creep. The presented experimental strategy has the potential to shed light on multi-phase processes associated with multiple geo-hazards.</p