Investigating the heterogeneity of the D″ region beneath the northern Pacific using a seismic array
Bibliographic record
Abstract
Seismic array recordings are used to study the heterogeneity of a 15° × 25° region of the lowermost mantle beneath the northern Pacific. We investigate P waves from northwestern Pacific events, 68° to 82° from the Yellowknife array in northern Canada. Anomalous arrivals (PdP) are observed 2–13.5 s after P with a slowness 0.4–1.2 s/deg smaller than P, suggesting that they are reflections from a D″ discontinuity. We use vespagrams (slant stacks) and f‐k analyses to determine travel times and slowness vectors respectively. The f‐k technique simultaneously estimates both the horizontal slowness and backazimuth of arrivals at a receiver, with better resolution than vespagrams. Travel time analysis reveals a mean discontinuity height of 241 km above the core‐mantle boundary in the region studied here. However, there appears a systematic variation in this thickness which ranges from 211 to 336 km. The f‐k analyses also reveal variations between P and PdP backazimuths, further implying the existence of lateral variations in D″ in this area. This site is thought to be a transition region from an area of mantle downwelling to a region of upwelling; thus the variations in heterogeneity in this region may be related to its proximity to a site of paleoslab accumulation.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".