Structure and serpentinization of the northern Cascadia mantle wedge corner from receiver function modelling
Bibliographic record
Abstract
The composition and structure of the mantle wedge corner (MWC) exert a primary control on seismogenic and fluid processes in subduction zone forearcs. Seismic evidence suggests widespread serpentinization of the MWC in Cascadia, but constraints on its internal structure and fabrics remain sparse. Here, we compile receiver function data for a line of seismograph stations in northern Cascadia to characterize the layered structure and seismic anisotropy in the MWC. We first invert for flat-layer shear-wave velocity (Vs) models and identify the presence of a dipping, ∼4 km thick seismic low-velocity layer (LVL) marked by low Vs (∼3 km/s) and high compressional-to-shear velocity ratio (Vp/Vs > 2). Above the LVL, the continental Moho is taken as the base of the low Vp/Vs (∼1.7) zone, previously interpreted as the silica-rich lower continental crust. Second, we solve for anisotropic parameters in the MWC, including layer thickness, Vp/Vs, percent anisotropy, and symmetry-axis orientation. We infer an ∼5 km thick layer at the base of the MWC with Vs of 3.6 km/s and Vp/Vs of ∼1.9. Anisotropy is characterized by a slow axis of hexagonal symmetry with 10% anisotropy and an orientation corresponding with sub-horizontal foliation fabrics. Based on these results, we infer 40%–100% serpentinization of the MWC localized within a thin layer above the plate interface shear zone, potentially hosting high pore-fluid pressure. Shear-induced foliated fabrics in serpentinites above the plate interface may play an essential role in controlling seismogenic processes by channelling fluids up dip and aiding in generating fluid overpressures.
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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) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".