Seismic Evidence for a Weakened Thick Crust at the Beaufort Sea Continental Margin

Estève, Clément; Liu, Yajing; Koulakov, Ivan; Schaeffer, A. J.; Audet, Pascal

doi:10.1029/2022gl100158

Cited by 4 publications

(9 citation statements)

References 38 publications

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“…Also, Estève et al. (2022) interpreted thick‐skinned crustal deformation locally beneath the eastern part of the Romanzof Uplift of northern Yukon. This region appears to have weakened thick crust at the Beaufort Sea continental margin due to high temperatures in the crust and upper mantle.…”

Section: Thermal Isostasy: Regional Elevation and Crustal Thicknessmentioning

confidence: 99%

“…Figure 14 shows the number of earthquakes versus depth for limited areas of NW Canada hot backarc areas, near the Beaufort Sea margin from Estève et al. (2022), and for the Denali fault zone area by Choi et al. (2021).…”

Section: Depth Extent Of Seismicitymentioning

confidence: 99%

“…To the east in the Yukon and western Northwest Territories, the seismicity and GPS relative motions show that deformation is complex, continuing far inland toward the edge of the craton at the Mackenzie Mountains thrust front and along the north-south mainly transcurrent Richardson Mountains extending to the margin of the Beaufort Sea (e.g., Cassidy et al, 2005;Estève et al, 2022;Hyndman, Flück, et al, 2005;Leonard et al, 2007Leonard et al, , 2008Marechal et al, 2015). As in the Alaska Brooks Range, the motion inland from the coastal collision has been interpreted to be transferred on a horizontal ductile detachment in the hot and weak backarc lower crust (Figure 2).…”

Section: Geological and Tectonic Regimementioning

confidence: 99%

“…Uppermost mantle earthquakes have a higher temperature limit of 600°C to 800°C, but these are uncommon. Figure 14 shows the number of earthquakes versus depth for limited areas of NW Canada hot backarc areas, near the Beaufort Sea margin from Estève et al (2022), and for the Denali fault zone area by Choi et al (2021). For hot backarc comparison, I show the depth distribution for the hot crust of California (Hauksson & Meier, 2019) and for the Cascadia western backarc (Hyndman et al, 2003).…”

Section: Depth Extent Of Seismicitymentioning

confidence: 99%

“…Figure 14. Depth extent of earthquakes in the hot backarc of NW Canada compared to the Cascadia hot arc/backarc, and the cold Cascadia forearc and cold Fennoscandian shield (afterEstève et al, 2022;Choi et al, 2021;Hauksson & Meier, 2019;Hyndman et al, 2003).…”

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confidence: 99%

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The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

Hyndman

2023

Geochem Geophys Geosyst

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NW Canada and Alaska are the continuation of the North American Cordillera through Mexico, western USA and western Canada. I show that they have similar thermal regimes and thermal control of tectonics and seismicity. I first summarize the multiple constraints to crust and upper mantle temperatures and then discuss some consequences. There are bimodal crust and upper mantle temperatures characteristic of most subduction zones: cool forearc, uniformly hot backarc (Yukon Composite Terrane to Southern Brooks Range, and Mackenzie Mountains), and stable cratonic backstops (Arctic Alaska Terrane and Canadian Shield). The main constraints are as follows: (a) Heat flow measurements, (b) Temperature‐dependent upper mantle velocities and seismic attenuation, (c) Temperature‐dependent topographic elevations; thermal isostasy, (d) Depth and temperature of the seismic lithosphere‐asthenosphere boundary (LAB), (e) Origin temperature and depth of craton kimberlite xenoliths, (f) Geochemically inferred source temperature and depth of recent volcanic rocks. (g) Depth to the magnetic Curie temperature, (h) Depth extent of seismicity. The backarc lithosphere is thin, LAB at 50–85 km and ∼1,350°C ± 25°C. Moho temperatures at 35 km are 850°C ± 100°C compared to cool cratonic areas of 400°C–500°C. The consequences include the following: (a) Thin and weak backarc lithosphere that accommodates pervasive tectonic deformation indicated by wide‐spread seismicity and GPS‐defined motions, in contrast to the stable cratonic regions; (b) Weak backarc lower crust that flattens the Moho and allows detachment and thrusting of the upper crust over the cold strong Arctic Alaska Terrane and Canadian Shield. This article provides a model for how to estimate deep temperatures from multiple constraints.

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Section: Thermal Isostasy: Regional Elevation and Crustal Thicknessmentioning

confidence: 99%

Section: Depth Extent Of Seismicitymentioning

confidence: 99%

Section: Geological and Tectonic Regimementioning

confidence: 99%

Section: Depth Extent Of Seismicitymentioning

confidence: 99%

mentioning

confidence: 99%

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The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

Hyndman

2023

Geochem Geophys Geosyst

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New Insights Into the Active Tectonics of the Northern Canadian Cordillera From an Enhanced Earthquake Catalog

Drooff,

Freymueller

2023

JGR Solid Earth

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Seismic activity in the Northern Canadian Cordillera is characterized by diffuse earthquakes that extend hundreds of km northwest from the Yakutat collision zone. We use 25 months of broadband seismic data from Mackenzie Mountain Earthscope Project (MMEP), USArray Transportable Array (TA), and permanent Canadian National Seismic Network stations to present a local earthquake catalog with high sensitivity to small regional events. Deep learning techniques are adopted for both seismic phase detection and association. Event relocations are performed to provide well constrained estimates of earthquake depth distributions. Clusters of seismicity spanning the upper crust are located in the central Richardson Mountains, along the Tintina fault, and in the northeast Selwyn Basin. These clusters suggest that the core of the Richardson Anticlinorium is tectonically active and that the Tintina fault is a locus for low levels of active deformation. We interpret seismicity in the northeast Selwyn Basin as primarily occurring in the hanging wall of the Plateau thrust fault and suggest that some combination of localized duplex structures and lithological strength contrasts both within the Selwyn Basin and between abutting Paleozoic shelf sequences may be responsible for seismicity in the Mackenzie Mountain foreland.

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Structure, origin, and deformation of the lithosphere in the northern Canadian Cordillera from high-resolution, passive-source seismic velocity models

Estève¹,

Audet

Schutt

et al. 2023

Preprint

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The recent deployment of temporary broadband seismic networks, notably the EarthScope USArray-Transportable Array (TA), has drastically improved the station coverage across northwestern Canada over the last ten years, enabling application of high-resolution passive-source seismic methods (i.e., seismic tomography, receiver functions and core phase shear wave splitting). This review highlights the main discoveries pertaining to the seismic velocity structure, origin and deformation of the lithosphere in the northern Canadian Cordillera (NCC). High-resolution seismic tomography models reveal that the lower crust in the NCC is marked by low velocity anomalies extending from the Gulf of Alaska to the Cordilleran deformation front, which are interpreted to reflect elevated temperatures that buoyantly support regional high elevations and potentially represent the seismic signature of strain transfer from the Yakutat collision zone to the Mackenzie Mountains. The Moho is relatively flat and shallow across the NCC, and is underlain by a thin layer of mantle lithosphere. Seismic velocity models further unveiled large-scale mantle structures associated with the unexposed Mackenzie craton in the north, and the Liard Transfer Zone in the south, which appear to buttress the NCC and further focus deformation in the eastern NCC. Seismic anisotropy and tomography provide evidence that the Tintina and Denali faults penetrate into the lithospheric mantle and played a first order role in shaping the present-day NCC. We propose that future studies should aim to: 1) resolve the shape of the Cordillera-craton boundary at upper mantle depths; 2) accurately estimate the lithosphere thickness in the NCC; and 3) improve coverage in the Beaufort Sea to understand the controls on convergent tectonics in the northern NCC.

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Seismic Evidence for a Weakened Thick Crust at the Beaufort Sea Continental Margin

Cited by 4 publications

References 38 publications

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

The Thermal Regime of NW Canada and Alaska, and Tectonic and Seismicity Consequences

New Insights Into the Active Tectonics of the Northern Canadian Cordillera From an Enhanced Earthquake Catalog

Structure, origin, and deformation of the lithosphere in the northern Canadian Cordillera from high-resolution, passive-source seismic velocity models

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