Deformation of the Pacific Plate west of the Queen Charlotte Fault
Date
2024-03-26
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Abstract
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.
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Keywords
Queen Charlotte Fault, Heat flow, Gravity, Strike-slip fault, stress perturbation, Crustal deformation
Citation
Perrin, R. (2024). Deformation of the Pacific Plate west of the Queen Charlotte Fault (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.