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Kinematics of the Fairweather-Queen Charlotte Transform System and Deformation Across the Broad Pacific-North America Plate Boundary Zone

The Fairweather-Queen Charlotte system is a 1200-km long onshore-offshore transform fault that stretches from British Columbia to southern Alaska. While the fault system is a active boundary with 6 M7+ earthquakes over the past century, major questions remain about how relative motion is accommodated across the region. Land-based geodetic data and offshore geomorphic data derived from high-resolution bathymetry suggest different rates of fault motion, which leads to different estimates of how much of the total estimated Pacific-North America motion is taken up by the fault system. Using Euler pole analyses and a combined geomorphic and geodetic dataset, I will develop an improved regional tectonic model that allows a more complete examination of the fault system and how motion is distributed through the plate boundary zone.

The plate configuration surrounding the Fairweather-Queen Charlotte system is complex. The Yakutat block, an oceanic plateau that moves to the northwest, sits to the west of the Fairweather and the northernmost Queen Charlotte fault. The Pacific plate is assumed to lie to the west of the central and southern Queen Charlotte fault. Based on geodetic data and Euler pole analyses, the Yakutat block and the Pacific move distinctly from each other. Geodetic data show that the coastal margin inboard of the fault system moves north relative to North America, implying that the fault system does not take up all relative motion. Adding geomorphic slip rate estimates to the geodetic data results in predicted motion rates along the Queen Charlotte fault with significantly lower degrees of convergence than previous geodetic models. These new rates require a Northeast Pacific block, which moves to the northwest at a rate different from either Yakutat or Pacific, to lie to the west of the central and southern Queen Charlotte fault. The predicted motion of the Northeast Pacific block is not compatible with right-lateral slip along the Gulf of Alaska shear zone, implying that additional blocks or internal deformation of the northeast Pacific may be required.

Session: Structure, Seismicity and Dynamics of the Queen Charlotte-Fairweather Fault System - I

Type: Oral

Room: Tubughnenq’ 5

Date: 5/1/2024

Presentation Time: 04:45 PM (local time)

Presenting Author: Julie Elliott

Student Presenter: No

Additional Authors