Crustal structure beneath the Strait of Juan de Fuca and southern Vancouver Island from seismic and gravity analyses
Bibliographic record
Abstract
Wide‐angle and vertical incidence seismic data from Seismic Hazards Investigations in Puget Sound (SHIPS), gravity modeling, and seismicity are used to derive two‐dimensional crustal models beneath the Strait of Juan de Fuca. The Eocene volcanic Crescent‐Siletz terrane is significantly thicker than previously recognized and extends from near the surface to depths of 22 km or greater. For the northern strait, a weak midcrustal reflector, dipping east from 12‐ to 22‐km depth, is inferred from wide‐angle reflections. A stronger deeper reflector, dipping eastward from 23‐ to 36‐km depth, is associated with the top of “reflector band E,” a zone of high reflectivity on coincident Multichannel Seismic (MCS) data, interpreted as a shear zone. A high‐velocity zone (7.60 ± 0.2 km s−1) between these reflectors is interpreted as a localized slice of mantle accreted with the overlying Crescent‐Siletz terrane. For the southern strait, no deep high‐velocity layer is observed and the E‐band reflectivity is weaker than to the north. A strong deep reflector, interpreted as the oceanic Moho dips eastward from 35 to 42 km. Seismicity within the subducting slab occurs mainly above the inferred oceanic Moho. Gravity modeling, constrained by the wide‐angle seismic models and seismicity, is consistent with the inferred large thickness of Crescent‐Siletz and high‐density rocks (3030 kg m−3) in the lower crust.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".