Investigating the lowermost mantle using migrations of long-period<i>S</i>-<i>ScS</i>data
Bibliographic record
Abstract
The lowermost mantle is investigated using a data set of high-quality waveforms and a phase stripping technique, which removes the S and ScS phases in order to isolate more subtle arrivals. Two migration methods were applied to locate scattering bodies in the lower mantle. The first, a simple backprojection, is useful for identifying regions of strong scattering. The second migration scheme uses weights based on the generalized Radon transform. We present results for a region of lower mantle beneath Alaska and western Canada, and test the influence of experimental geometry on the migration results by migrating synthetic data sets generated for various distributions of point scatterers. We show that, although the exact geometry of scattering bodies is poorly constrained, the majority of the features in the data can be recreated with a few simple structures. The results show the presence of a D″ discontinuity, which can be simulated using a flat scattering body ∼250 km above the core–mantle boundary near the Alaska–Canada border. We also present evidence for positive velocity anomalies in the bottom 100 km of the mantle, beneath the D″ reflector and near the Aleutians. The association of these scattering structures with a region of high velocity is consistent with a cause related to lower mantle heterogeneity introduced by a subducting slab.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 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 teacher head, 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".