Frequency of large crustal earthquakes in Puget Sound–Southern Georgia Strait predicted from geodetic and geological deformation rates
Bibliographic record
Abstract
Earthquake hazard in the Cascadia subduction zone forearc comes from three sources: great subduction earthquakes, Wadati–Benioff slab events, and earthquakes in the forearc crust. This study deals with a concentration of forearc crustal earthquakes in the Puget–Georgia region of southwestern Canada and northwestern United States. These earthquakes are due to margin‐parallel shortening, rather than compression in the direction of plate convergence. The frequency of large earthquakes has previously been based mainly on extrapolation of the statistics of smaller events from the short instrumental record. In this study, an independent estimate has been obtained through the seismic moment rate required to accommodate current rates of deformation from GPS and geological data. The catalogue statistics to Mx = 7.5 give a moment rate of 4.0 × 10 17 Nm/yr and a shortening rate of 2.9 mm/yr if all deformation is seismic. GPS data indicate local current N–S shortening of 3 ± 1 mm/yr. For a seismogenic thickness of 12 km, this deformation represents a moment rate of 4.1 × 10 17 Nm/yr. The predicted occurrences are 0.022/yr (45 years) for M > 6, and 0.0025/yr (400 years) for M > 7, within the uncertainties of the catalogue statistics. Large characteristic earthquakes are not required. Forearc long‐term average motion based upon larger‐scale GPS, paleomagnetic, and geological data ranges from 5 to7 mm/yr. The estimated long‐term occurrence of large events thus is approximately double the current rate, and we infer that the extra earthquakes could follow abrupt N–S shortening in this part of the forearc associated with the oblique rupture motion of great subduction events.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 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 | 0.001 |
| 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 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".