Variations in Seismic Wave Speed and <i>V</i><sub><i>P</i></sub>/<i>V</i><sub><i>S</i></sub> Ratio in the North American Lithosphere
Bibliographic record
Abstract
Abstract Seismic wave speed is controlled by a number of factors, including temperature and chemical composition, as well as the presence of volatiles and partial melt. Tomography provides a powerful constraint on wave speed variations, but if only V P or V S variations are imaged, it is challenging to separate the competing effects of these factors and make a full interpretation of seismic anomalies. In this study, we generate models of variations in the V P / V S ratio, which introduce new constraints on geologic structures, compositions, and processes. We invert P and S wave arrival times, as well as Rayleigh wave phase velocities, utilizing the sensitivity of Rayleigh waves to both V P and V S to form mutually constrained but independent models of V P and V S structure at lithospheric depths below the continental United States and Southeastern Canada. From this we can examine variations in V P / V S , highlighting a distinct pattern of anomalies which are less readily observed in V P or V S alone. A clustering analysis is performed to relate 1‐D profiles of wave speed as a function of depth to tectonic provinces. While the first‐order structure of V P and V S appears to be dominated by the thermal contrast between the Eastern and Western United States, the strongest control over V P / V S ratio perturbations within the mantle lithosphere appears to be the presence of melt. Certain higher‐ V P / V S anomalies within the cratonic interior may reflect compositional anomalies and variations in Moho structure. This work provides a continental‐scale framework for future quantitative analyses of thermal and compositional heterogeneity, and for targeted geologic interpretation.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".