Rayleigh wave azimuthally anisotropic phase velocity maps beneath western Canada
Bibliographic record
Abstract
Abstract The lithospheric evolution of western Laurentia spans several billion years of Earth history and provides an exceptional opportunity for investigating continental deformation during Archean and Proterozoic assembly of the craton and subsequent Phanerozoic orogenic processes along its western margin. In this study we present fundamental‐mode Rayleigh wave azimuthal anisotropy in the period range 20–150 s for western Laurentia and the southern Canadian Cordillera. The surface wave phase velocity maps offer new constraints on the depth distribution of seismic anisotropy in this region. At short periods (20–25 s), strong anisotropy with an orogen‐parallel fast direction is evident in the Cordillera and neighboring foreland belt, suggesting pervasive ductile deformation in the lower crust during Laramide orogenesis. At periods of 70 s and higher, a zone of low‐to‐null azimuthal anisotropy is evident in the southern part of the Cordillera. This apparent null region is interpreted to reflect complex asthenospheric flow due to the combined effects of the Juan de Fuca slab window, lithospheric delamination, and small‐scale edge‐driven convection. Depth‐variant azimuthal anisotropy is evident beneath the cratonic part of the study region. The dominant direction of fast wave propagation in the southeastern part of the craton changes from N‐S at periods of <120 s to NE‐SW at 150 s period. This depth dependence is inferred to arise from different origins of the observed anisotropy, with “frozen” anisotropy within cratonic lithosphere underlain by flow‐driven anisotropy in the asthenosphere. The frozen N‐S trending fabrics in the middle to lower cratonic lithosphere most likely reflect processes of Paleoproterozoic assembly of western Laurentia.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| 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".