D″ beneath the Arctic from inversion of shear waveforms
Bibliographic record
Abstract
The structure of the D″ region beneath the Arctic has not previously been studied in detail. Using waveform inversion, we find that the average S‐wave velocity in D″ beneath the Arctic is about 0.04 km/s higher than PREM, which is consistent with the existence of post‐perovskite (ppv) in D″. It is difficult to strongly constrain the fine structure of S‐velocity within D″ due to the small number of stations at epicentral distances Δ < 90°, but by weighting those stations heavily in the inversion, we show that the data suggest the existence of high S‐velocity in the upper half of D″ and low S‐velocity in the lower half, consistent with the possibility of a double crossing (ppv → pv reverse phase transition) within D″. We conduct a computational experiment to show that resolution of the velocity structure within D″ could be significantly improved by temporary installation of a portable array of seismographs in northern Canada, which would greatly increase the number of stations in the range 70° < Δ < 90°.
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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 | 0.001 |
| Science and technology studies | 0.000 | 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) | 0.001 | 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".