Viscosity of the asthenosphere from glacial isostatic adjustment and subduction dynamics at the northern Cascadia subduction zone, British Columbia, Canada
Bibliographic record
Abstract
Late glacial sea level curves located in the Cascadia subduction zone (CSZ) fore arc in southwestern British Columbia show that glacial isostatic adjustment (GIA) was rapid when the Cordilleran Ice Sheet collapsed in the late Pleistocene. GIA modeling with a linear Maxwell rheology indicates that the observations can be equally well fit across a wide range of asthenospheric thicknesses, provided that the asthenospheric viscosity is varied from 3 × 10 18 Pa s for a thin (140 km) asthenosphere to 4 × 10 19 Pa s for a thick (380 km) asthenosphere. Present‐day vertical crustal motion predicted by the GIA models shows rates of a few tenths of a millimeter per year, consistent with previous analyses. The model viscosities largely pertain to the viscosity of the oceanic mantle beneath the subducting Juan de Fuca slab but include a contribution from the mantle wedge above the slab. For comparison, effective viscosities for the upper mantle due to the tectonic regime (subduction) were computed using the strain rates and temperatures of an independent geodynamic model of the CSZ with a wet olivine power law rheology. The effective viscosities agree well with GIA model viscosities of 10 19 Pa s or less, corresponding to an asthenosphere of 100 or 200 km thickness. The agreement suggests a significant role for power law flow in the GIA response. Regardless of the microphysical mechanisms responsible for the GIA response, the viscosity values inferred from GIA can be applied to studies of the megathrust earthquake cycle because both processes take place on comparable time scales.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 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) | 0.001 | 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 teacher head, 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".