Two-station Rayleigh wave tomography of Canada
Bibliographic record
Abstract
Seismic tomography is a common method used to study the lithosphere and can reveal evidence of past and present tectonic and geodynamic processes. In largely aseismic areas such as central and eastern Canada, single-station measurements of surface-wave dispersion will provide limited and uneven resolution; two-station measurements allow the use of a larger selection of earthquakes (i.e., extending to teleseismic events) while still preserving a regional-scale measurement. This work examines seismic velocity and anisotropy variations of the Canadian lithosphere using two-station-based surface-wave tomography, to obtain new insights into the formation history of the continent. A cross-correlation method was used to obtain new two-station dispersion curves (a total of 117) which were added to a dataset of previously published measurements. These were chosen to fill in gaps in ray coverage and to maximize azimuthal distribution, particularly across the Prairies and the Cordillera. Tomographic inversion was used to calculate anisotropic phase velocity maps for periods of 15-400 s, following outlier exclusion and resolution testing. The phase velocity maps show that the low velocity Cordilleran lithosphere contains two southern zones (west and east) with different anisotropy, which are interpreted to be due to the influence of the subducting Juan de Fuca plate in the west. A sharp Cordillera-craton boundary with the Canadian Shield is also noted, which shifts eastward near the US border. A very low velocity anomaly is observed beneath southeastern Saskatchewan which is likely linked to a mantle suture in this area. The highest velocities are seen beneath the craton, with particularly high velocities in Nunavut (northern Canada) and the western Superior Province. Strong E-W anisotropy is observed beneath the western Superior resulting from frozen lithospheric fabric. A clear distinction between the Precambrian Shield and the lower velocity Appalachian domains is also noted. This Appalachian low velocity zone is thought to be associated with the present-day Northern Appalachian Anomaly, rather than the Great Meteor Hotspot track.
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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 | 0.002 | 0.004 |
| 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) | 0.003 | 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".