Browsing by Author "Perrin, Robert"

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    A simplified down-hole method for monitoring an engineered hydraulic barrier using electrical resistivity tomography
    (2018-03-15) Perrin, Robert; Pidlisecky, Adam; Karchewski, Brandon; Lamoureux, Michael Phillip; Lauer, Rachel M.
    In the Athabasca Oil sands in Northern Alberta one of the major risks to mining operations is water infiltration from a saline aquifer at the base of the oil sands. One method of preventing infiltration is by the use of a freeze wall surrounding the mine pit. Monitoring a freeze wall of this scale can be difficult because of the scale of oil sands mining pits. This thesis explores the use of single-borehole electrical resistivity tomography (ERT) as a method of monitoring the entire freeze wall for leaks, which takes advantage of the freeze wall infrastructure to minimize monitoring costs. The study was conducted by modelling a freeze wall breach, and then simulating an ERT data series from electrode arrays attached to the outside of the freeze pipes that were used to create the freeze wall. By using the freeze pipes for monitoring, the entire wall can be monitored while eliminating the need to drill additional wells for monitoring. The resulting simulated data were inverted using a simplified parameterized inversion scheme and were analyzed for their potential to show a leak in the freeze wall. The results of the study indicated that the use of single-borehole ERT can be used to monitor for leaks along the entire freeze wall, and the inverted models can be used to automate a corrective action to fix the freeze wall at a leak location. The results also indicated that determining the volume of saline water that has leaked is not possible using this simplified inversion scheme.
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    Deformation of the Pacific Plate west of the Queen Charlotte Fault
    (2024-03-26) Perrin, Robert; Lauer, Rachel; Karchewski, Brandon; Pidlisecky, Adam; Tutolo, Benjamin; Innanen, Kristopher; Schaeffer, Andrew
    The Queen Charlotte Fault (QCF) is a transform fault that stretches from Haida Gwaii to Icy Point, Alaska, and has been of particular interest since an earthquake in 2012 demonstrated its geohazard potential. Observations made along the margin since then have raised questions about how deformation is distributed around the fault. Firstly, plate motion along the QCF is aligned with the fault apart from its southern section, where there is slight convergence between the Pacific and North American plates. While some evidence suggests the convergence may be accommodated by thickening of the Pacific Plate, there are uncertainties about how this is distributed along the QCF. Secondly, along the southern QCF lies the Queen Charlotte Terrace and several oblique faults. These features extend approximately 30 km west of the fault and are thought to be part of the mechanism that accommodates transpression along the southern QCF. This raises questions about why they are limited to this distance, and what the zone of influence of the fault might be. Finally, deformation of the Pacific Plate is controlled by lithospheric strength, which is a function of both thickness and temperature. Thick sediments west of the QCF, should allow young crust to be warmer than areas that are lightly sedimented. The limited heat flow observations that exist along the QCF, however, show a heat flow deficit, suggesting the crust may be cooler than expected. This raises questions about the thermal state of the crust, and how that may impact crustal deformation. This study examines these observations using several existing geophysical datasets. This study shows that the crust appears to be thicker than typical oceanic crust along Haida Gwaii. I also show that the zone of influence of the QCF is related to the dominant geometrical wavelengths of the fault and is consistent with observed deformation. Finally, I examine the thermal state of the crust to show that crustal cooling by hydrothermal circulation is likely occurring. The conclusions from this study improve our understanding of deformation of the Pacific Plate and underscore the need for continued studies along the QCF.