Bibliographic record
Abstract
The Juan de Fuca plate subducts along the west coast of North America along a plate boundary that extends some 1000 km from northern California to Vancouver Island. In map view, the plate boundary is nearly straight along its northern and southern regions, but exhibits a 35° change in orientation offshore from northern Washington State. Landward from this bend is an arch in the shape of the subducting plate, a concentration in Wadati - Benioff seismicity and an anomalously thick Miocene accretionary prism that makes up the two kilometer-high Olympic Mountains. We speculate that all three are related, directly or indirectly, to the fact that the Cascadia slab is subducting into a concave, oceanward corner which creates a geometric space problem analogous to pleats in a tablecloth hanging off the corner of a table. To test this hypothesis, we develop a theory of steady state, incompressible three-dimensional fluid flow that is asymptotically valid for a thin slab with high linear (or non-linear) viscosity relative to the surrounding fluid. Flow in this simple model is constrained by kinematic boundary conditions rather than buoyancy forces. Fixing the slab geometry to the same trench-normal profile along the entire subduction zone, we invert for the flow field that minimizes the dissipation power of the system and find that strain rates, characterized by along-strike compression, are concentrated along the west coast of Washington, reaching values of 2x10-16 s-1. In a second experiment, we constrain the same 20° dip along the northern and southern edges of the subducting plate and find that the optimal slab geometry contains an arch in a location similar to the seismologically observed arch, and that the root-mean square of the strain rates are reduced by a factor of five. Thus, if these strain rates are accommodated by intraplate earthquakes, this arching model provides a geometry that allows a five-fold reduction in seismic moment release rates. The predicted strain rates are consistent with the observed moment release rate associated with one Mw=7 and several Mw>6 earthquakes per century in the Olympic Mountain/Puget Sound region, and a much lower rate to the north and south. Predicted strain rates associated with slab bending and unbending are generally smaller than the predicted membrane strain rates. The anomalously thick accretionary prism associated with the Olympic Mountains can be explained by the critical taper theory as being caused by the shallow dip of the slab along the arch.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 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".