Surface‐Wave Tomography of the Northern Canadian Cordillera Using Earthquake Rayleigh Wave Group Velocities
Bibliographic record
Abstract
Abstract We measure fundamental‐mode Rayleigh wave group velocity dispersion from regional earthquakes and employ transdimensional Bayesian tomography to invert for azimuthally anisotropic group velocity maps at 10–60 s periods. Seismic azimuthal anisotropy within the crust and uppermost mantle shows fast‐axis alignment with principal northern Canadian Cordillera (NCC) tectonic structures suggesting large‐scale and coherent deformation across the crust and upper mantle. We extract group velocity dispersion curves at each grid point of the isotropic group velocity maps and invert them independently for VS as a function of depth in a probabilistic framework. At mid‐to‐lower crustal depths, our pseudo 3‐D VS model reveals an anomalously low VS structure (<3.8 km/s) across the NCC, which likely reflects elevated crustal temperatures that buoyantly support regional high elevations. Two high‐velocity regions (≥4.5 km/s) at uppermost mantle depths underpin the edges of the arcuate Mackenzie fold and thrust belt. We observe variations in the dip direction of the high‐velocity craton edge in the upper mantle, from subvertical in the northern NCC to westward in the southern NCC. We interpret a low‐velocity region (≤4.3 km/s) between the Tintina and Denali faults at uppermost mantle depths to reflect upwelling asthenosphere, which likely postdates 430 km of previously estimated Eocene lithosphere‐scale horizontal displacement along the Tintina fault. Our surface‐wave model resolves a high‐velocity region (≥4.4 km/s) dipping north‐northeast below the Wrangell volcanic field, which we interpret as a down‐going segment of the Pacific slab and may contribute to the observed volcanism in the area.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.002 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".