| Title | Plate boundary localization, slip-rates and rupture segmentation of the Queen Charlotte Fault based on submarine tectonic geomorphology |
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| Author | Brothers, D S; Miller, N C; Barrie, J V ; Haeussler, P J; Greene, H G; Andrews, B D; Zielker, O; Watt, J; Dartnell, P |
| Source | Earth and Planetary Science Letters vol. 530, 115882, 2020 p. 1-16, https://doi.org/10.1016/j.epsl.2019.115882  Open Access |
| Image |  |
| Year | 2020 |
| Alt Series | Natural Resources Canada, Contribution Series 20200180 |
| Publisher | Elsevier |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | British Columbia |
| Area | Alaska; United States of America |
| Lat/Long WENS | -140.0000 -132.0000 60.0000 50.0000 |
| Subjects | Nature and Environment; Science and Technology; surficial geology/geomorphology; tectonics; fault zones; faults; faults, transform; bathymetry; outwash; glacial deposits; glacial erosion; plate
boundaries; continental slope; Queen Charlotte Fault; Fairweather Fault; Chatham Strait Fault; Transition Fault; Aja Fracture Zone |
| Illustrations | location maps; bathymetric profiles; tables; satellite imagery; distribution diagrams; plots; models |
| Released | 2020 01 15 |
| Abstract | Linking fault behavior over many earthquake cycles to individual earthquake behavior is a primary goal in tectonic geomorphology, particularly across an entire plate boundary. Here, we examine the
1150-km-long, right-lateral Queen Charlotte-Fairweather fault system using comprehensive multibeam bathymetry data acquired along the Queen Charlotte Fault (QCF) offshore southeastern Alaska and western British Columbia. Fine-scale analysis of
tectonic geomorphology allowed us to identify and reconstruct 184 strike-slip piercing points over a 630 km stretch of the QCF. Age constraints from glacial recession and offshore sedimentation patterns yield a consistent slip-rate of similar to
50-57 mm/yr since similar to 17-12 ka, the fastest rate for a continent-ocean strike-slip fault on Earth. These slip-rates equal or exceed estimates of Pacific-North America (PA-NA) relative motion from global plate reconstructions, indicating that
PA-NA motion is highly localized. The QCF cuts the seafloor along a narrow and unusually straight trace for its entire length and multiple fault traces are observed only at local step-overs. The geometry and behavior of the QCF over many earthquake
cycles is simple and typical of mature faults with relatively homogeneous stress fields. Since the QCF is the primary PA-NA plate boundary, we used the trace of the QCF to define the small circle path for relative plate motion and computed the
associated Euler pole. Predicted along-strike obliquity variations based on the new pole agree with observed tectonic geomorphology and suggest that previous global plate reconstructions overestimated the degree of oblique convergence along the QCF.
We also find that subtle, long-wavelength (75-150 km) bends and discrete step-overs appear to define the endpoints of M>7 earthquakes, suggesting that obliquity and resultant fault geometry may control rupture segmentation and asperity development.
Lastly, the agreement between predicted obliquity and tectonic geomorphology along the entire length of QCF compelled a reevaluation of regional tectonic models. In the north, the eastern Yakatat Terrane appears to be translating northwest with the
Pacific plate, and slip transferred from the QCF to the Fairweather Fault results in similar to 20 mm/yr of convergence along the southern St. Elias mountains. In the south, we predict a reduced rate of convergence along the QCF west of Haida Gwaii
(similar to 5-6 mm/yr of shortening, on average) relative to previous studies. Our results support a model for transpression and strike-slip partitioning along the edge of a hot and weak Pacific Plate, leading to crustal thickening and growth of the
Queen Charlotte Terrace to the west of Haida Gwaii. |
| GEOSCAN ID | 326592 |
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