Three-dimensional viscoelastic interseismic deformation model for the Cascadia subduction zone
Bibliographic record
Abstract
Contemporary deformation of the Cascadia forearc consists of an elastic interseismic strain build-up as part of the subduction earthquake deformation “cycle” anda secular deformation primarily in the form ofarc-parallel translation and clockwise rotationofforearc blocks. Athree-dimensional (3-D) elastic dislocation model, constrainedby vertical deformation data, was developed previously to study the interseismic deformation. In this study, we develop a 3-D viscoelastic finite element model for the Cascadia subduction zone to study the temporal and spatial variations of interseismic deformation, and we compare the model results primarily with horizontal geodetic deformation observations. The model has an elastic lithosphere/slab and a viscoelastic mantle which has a viscosity of 10 19 Pa s as constrained by recent postglacial rebound analyses. For comparison, we adopt a seismogenic zone geometry that was used in the previous elastic dislocation model, and we test the effects of different estimates of relative plate motion on the model predictions. Interseismic deformation is simulated by assigning a backslip rate to the locked zone of the subduction fault, preceded by an earthquake rupture of the same zone. Based on preliminary model results, we draw the following conclusions: (1) The deformation rate decreases through the interseismic period. A seaward motion is predicted for inland sites early in the interseismic period, an effect of postseismic creep of the mantle. (2) Model strain rates 300 years after the earthquake are consistent with the observed values, regardless of the plate motion models used. The horizontal velocities in northern Cascadia decrease landward at a slower rate than predicted by the elastic dislocation model, providing a better fit to observations. (3) Oblique subduction causes strain partitioning. As a result, the direction of local maximum contraction is much less oblique than plate convergence. The northerly direction of the GPS velocities in southern Cascadia represent a northward translation of the forearc. The secular deformation of the forearc may be partially accommodated through earthquake deformation cycles, but it may be better modeled as a process independent of the earthquake cycle.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".