The Queen Charlotte Fault, British Columbia: seafloor anatomy of a transform fault and its influence on sediment processes

Barrie, J. Vaughn; Conway, Kim W.; Harris, Peter T.

doi:10.1007/s00367-013-0333-3

Cited by 32 publications

(24 citation statements)

References 21 publications

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“…6), recent very high-resolution bathymetry and acoustic imaging shows that this fault is nearly purely transcurrent at the seafloor (Fig. 12) (Barrie et al, 2013); (2) the M s 8.1 earthquake of 1949 that ruptured over 200 km from the central islands to the north off southern Alaska, had a dominantly strike-slip mechanism (Chandra, 1974;Rogers, 1986;Bérubé et al, 1989;Nishenko et al, 1990). Also, local seismicity located with temporary land and ocean-bottom seismograph stations was mainly beneath the surface trace of the QCF, most at a depth of 15-20 km (Hyndman and Ellis, 1981;Bérubé et al, 1989;Bird, 1997) so the main fault must be nearly vertical.…”

Section: Subduction Initiationmentioning

confidence: 93%

“…Swath bathymetry and acoustic imaging show what may be an active volcanic seamount even farther north off the southernmost Haida Gwaii, so the northward migration of the triple junction may be continuing (Barrie et al, 2013). The Dellwood and Wilson spreading centers have produced an area of very young oceanic crust at the northwest end of the Winona basin (e.g., Chase, 1977;Riddihough et al, 1980).…”

Section: Winona Basinmentioning

confidence: 98%

“…The southern portion lies just off the west coast of the islands of Haida Gwaii (formerly Queen Charlotte Islands; Fig. 1) (e.g., Riddihough andHyndman, 1989: Nishenko andJacob, 1990;Hyndman and Hamilton, 1993;Rohr and Furlong, 1995;Scheidhauer, 1997;Mazzotti et al, 2003;Barrie et al, 2013;Walton et al, 2013). Farther to the south, the Cascadia Subduction zone (CSZ) separates this transform fault zone from the transcurrent San Andreas fault zone.…”

Section: Introductionmentioning

confidence: 98%

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Tectonics and Structure of the Queen Charlotte Fault Zone, Haida Gwaii, and Large Thrust Earthquakes

Hyndman

2015

Bulletin of the Seismological Society of America

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This article provides a summary of the structure and tectonic history of the Queen Charlotte transform fault zone off western Canada, as background to understanding the 2012 M w 7.8 thrust earthquake off Haida Gwaii. There was margin subduction prior to the Eocene. The fault zone then became the mainly transcurrent Pacific-North America boundary. There was mid-Tertiary oblique extension, then 15°-20°oblique convergence from ∼6 Ma to the present that resulted in underthrusting and subduction initiation. The total underthrusting has been too small for BenioffWadati seismicity or arc volcanics but is indicated by (1) a trench, the Queen Charlotte Trough, into which the oceanic plate bows downward and an offshore flexural bulge, the Oshawa rise; (2) the Queen Charlotte terrace, an accretionary sedimentary prism;(3) seismic receiver function delineation of the underthrusting Pacific plate; (4) heat flow decreasing landward as predicted for underthrusting; (5) low gravity offshore and high onshore, consistent with underthrusting; and (6) late Tertiary uplift and erosion of the west coast of the islands. Oblique convergence is partitioned into nearly marginnormal underthrusting (i.e., M w 7.8 event) relative to the terrace, which is moving along the margin, and margin parallel on the Queen Charlotte strike-slip fault just off the coast that produced the 1949 M s 8.1 earthquake. Landward on the mainland, Global Positioning System data suggest slow coast-parallel shear with no historical seismicity. The convergence rate decreases to the north of Haida Gwaii off Dixon Entrance, but large thrust earthquakes are possible. To the south, underthrusting of the Winona basin margin also could generate large earthquakes.

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Section: Subduction Initiationmentioning

confidence: 93%

Section: Winona Basinmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 98%

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Tectonics and Structure of the Queen Charlotte Fault Zone, Haida Gwaii, and Large Thrust Earthquakes

Hyndman

2015

Bulletin of the Seismological Society of America

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“…The 100 m resolution UNCLOS data were merged with ETOPO1 1 arc-min global relief data (Amante and Eakins, 2009; see also Data and Resources) and used primarily as a background map for reference. The southernmost QCF has new, high-resolution multibeam coverage and is discussed in a study by Barrie et al (2013) and Rohr (2015).…”

Section: Datamentioning

confidence: 99%

“…The morphology of the QCT is variable along strike, with the main trace of the QCF sometimes marked by half-grabens and other times by a narrow ridge (Rohr et al, 2000). Recent mapping on the QCF south of 53°N also indicates small pull-apart basins along strike (Barrie et al, 2013).…”

Section: Observations Faultsmentioning

confidence: 99%

Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures

Walton

Gulick

Haeussler

et al. 2015

Bulletin of the Seismological Society of America

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The Queen Charlotte fault (QCF) is a dextral transform system located offshore of southeastern Alaska and western Canada, accommodating ∼4:4 cm=yr of relative motion between the Pacific and North American plates. Oblique convergence along the fault increases southward, and how this convergence is accommodated is still debated. Using seismic reflection data, we interpret offshore basement structure, faulting, and stratigraphy to provide a geological context for two recent earthquakes, an M w 7.5 strike-slip event near Craig, Alaska, and an M w 7.8 thrust event near Haida Gwaii, Canada. We map downwarped Pacific oceanic crust near 54°N, between the two rupture zones. Observed downwarping decreases north and south of 54°N, parallel to the strike of the QCF. Bending of the Pacific plate here may have initiated with increased convergence rates due to a plate motion change at ∼6 Ma. Tectonic reconstruction implies convergence-driven Pacific plate flexure, beginning at 6 Ma south of a 10°bend the QCF (which is currently at 53.2°N) and lasting until the plate translated past the bend by ∼2 Ma. Normal-faulted approximately late Miocene sediment above the deep flexural depression at 54°N, topped by relatively undeformed Pleistocene and younger sediment, supports this model. Aftershocks of the Haida Gwaii event indicate a normal-faulting stress regime, suggesting present-day plate flexure and underthrusting, which is also consistent with reconstruction of past conditions. We thus favor a Pacific plate underthrusting model to initiate flexure and accommodation space for sediment loading. In addition, mapped structures indicate two possible fault segment boundaries along the QCF at 53.2°N and at 56°N.

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Deformation of the Pacific/North America Plate Boundary at Queen Charlotte Fault: The Possible Role of Rheology

et al. 2018

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The Pacific/North America (PA/NA) plate boundary between Vancouver Island and Alaska is similar to the PA/NA boundary in California in its kinematic history and the rate and azimuth of current relative motion, yet their deformation styles are distinct. The California plate boundary shows a broad zone of parallel strike slip and thrust faults and folds, whereas the 49‐mm/yr PA/NA relative plate motion in Canada and Alaska is centered on a single, narrow, continuous ~900‐km‐long fault, the Queen Charlotte Fault (QCF). Using gravity analysis, we propose that this plate boundary is centered on the continent/ocean boundary (COB), an unusual location for continental transform faults because plate boundaries typically localize within the continental lithosphere, which is weaker. Because the COB is a boundary between materials of contrasting elastic properties, once a fault is established there, it will probably remain stable. We propose that deformation progressively shifted to the COB in the wake of Yakutat terrane's northward motion along the margin. Minor convergence across the plate boundary is probably accommodated by fault reactivation on Pacific crust and by an eastward dipping QCF. Underthrusting of Pacific slab under Haida Gwaii occurs at convergence angles >14°–15° and may have been responsible for the emergence of the archipelago. The calculated slab entry dip (5°–8°) suggests that the slab probably does not extend into the asthenosphere. The PA/NA plate boundary at the QCF can serve as a structurally simple site to investigate the impact of rheology and composition on crustal deformation and the initiation of slab underthrusting.

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The Queen Charlotte Fault, British Columbia: seafloor anatomy of a transform fault and its influence on sediment processes

Cited by 32 publications

References 21 publications

Tectonics and Structure of the Queen Charlotte Fault Zone, Haida Gwaii, and Large Thrust Earthquakes

Tectonics and Structure of the Queen Charlotte Fault Zone, Haida Gwaii, and Large Thrust Earthquakes

Basement and Regional Structure Along Strike of the Queen Charlotte Fault in the Context of Modern and Historical Earthquake Ruptures

Deformation of the Pacific/North America Plate Boundary at Queen Charlotte Fault: The Possible Role of Rheology

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