Slow Slip in the Cascadia Subduction Zone: Thinking Outside the Plane
Bibliographic record
Abstract
Abstract In the Cascadia subduction zone beneath Vancouver Island a major (Mw 6–7) slow slip event and accompanying tremor occur about every 14 months at depths between ∼30 and 45 km. The total slip during an event is between 2 and 4 cm, which is significantly less than the 4.4 cm of plate convergence over the 14‐month recurrence interval. We propose that large slow slip events occur within a relatively thin (<500 m) shear zone in the upper layer of the subducting oceanic crust and that the ∼1–2 cm of missing slip is accommodated by creep in an overlying layer of parallel, seismic reflectors (the E‐layer) during the 14 months between events. We suggest that this creep is instrumental in the formation of the E‐layer. We show that a simple two‐layer model, where a viscoelastic E‐ layer overlies an elastic oceanic crust, can quantitatively match observed constraints if viscosity in the E‐layer is in the range and the shear strength of the interface is in the range . The low viscosity is consistent with other estimates for shear zones in the lower crust. The low shear strength is consistent with the value inferred from tremor triggering by surface waves from large earthquakes and with a frictional instability where fluid pressures are near‐lithostatic.
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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 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.002 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".