Shear Velocity and Radial Anisotropy beneath Southwestern Canada: Evidence for Crustal Extension and Thick‐Skinned Tectonics
Bibliographic record
Abstract
Abstract Deformation‐associated craton assembly and Cordilleran orogenesis played major roles during the crustal formation beneath the western margin of North America. To improve the understanding of the deformation history in this region, we investigate the crustal shear velocity and anisotropy by analyzing fundamental mode Rayleigh and Love waves from ambient seismic noise. Continuous recordings from 118 regional broadband stations reveal lateral variations in both velocity and anisotropy with strong spatial affinities to major geological domains. Strong variations in radial anisotropy, which dips westward and extends to at least midcrustal depths, suggest a “thick‐skinned” foreland thrust‐and‐fold belt beneath the Canadian Rocky Mountains. Our regional data also suggest increased horizontal shear velocities beneath the southern Canadian Cordillera, particularly near the Omineca Belt, which may have resulted from strong zonal deformation within the Cordilleran crust. This anisotropic anomaly migrates southward, and its spatial extent agrees well with the normal fault distribution to the west of the Rocky Mountain Trench. Our observations offer new evidence for the Eocene extension of the orogenic hinterland during the trans‐tensional motion of the Cordillera to the North American craton.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.002 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".