Multi-scale remote sensing to characterize crustal faulting in the northern Pacific Cordillera
Date
2025
Authors
Salomon, Guy William
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Abstract
Crustal earthquakes pose significant hazard to people all around the world, and because these events occur infrequently, relative to interplate earthquakes, they remain poorly understood. This dissertation is composed of three projects which share common themes of characterizing the geometries, kinematics, and activity of crustal faults within the northern Pacific Cordillera by making use of remote sensing techniques, albeit at several spatial scales. This region is vast with limited access which makes traditional, boots-on-the-ground fieldwork challenging and expensive. Remote sensing allows us to gather significant insights into the region from afar and focus, or motivate, future research. I begin by using InSAR and seismological analyses to study a recent earthquake within the Koryak Highlands of eastern Siberia. This is one of the most northerly earthquakes to be studied using InSAR, with additional challenges of steep terrain and snow cover; these issues were overcome by the short revisit times offered by the Sentinel-1 satellites. Understanding this event has implications for seismic hazard assessment in other parts of the cordillera, such as Alaska and western Canada which have similar crustal structures. This study highlights that previously unknown, immature faults within known suture zones can produce moderate to large earthquakes. In the second project, I describe a novel uncrewed aerial vehicle (UAV) laser scanning (ULS) platform which can be used to collect inexpensive, high-resolution topography even beneath dense vegetation. I showcase four datasets collected by this platform, across several different landscapes and vegetation types in western Canada, comparing these with conventional airborne laser scanning (ALS) and Structure-from-Motion (SfM) datasets. The ULS offers improved point density and vegetation penetration compared to ALS and SfM, creating high-resolution topographic models and allowing fine-scaled features to be identified. It also offers opportunities for rapidly collecting perishable data such as along surface ruptures of recent earthquakes and potentially could be used to capture afterslip. The last project uses ALS and ULS, as well as near-surface geophysics and field observations, to investigate whether the San Juan fault on southern Vancouver Island has been active during the Quaternary. I find a 6 km long, 30 m high scarp cutting across glacial sediments. The up-thrown southern side being composed of rheologically weaker schists and volcanics, leads me to infer that the fault has been recently active in order to have generated this feature, and that this scarp likely represents many earthquake cycles. I also find an uphill-facing scarp offsetting colluvium, which may represent the most recent rupture (late Quaternary) along the San Juan fault. Several potential targets for future paleoseismic studies are identified. In all, these works demonstrate the importance of a multi-disciplinary approach when studying active tectonics, and highlight the usefulness of remote sensing techniques for initial observations of continental deformation.
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Keywords
Crustal faulting, InSAR, Lidar, Cascadia, Active tectonics, Geomorphology