Ring-Shaped Seismicity Structures in the Cascadia Subduction Zone: Possible Upcoming Large Earthquakes
Bibliographic record
Abstract
Abstract Seismicity characteristics in the Cascadia subduction zone located west of North America are considered. It has been established that, since 1964, shallow (h = 0–33 km) ring-shaped seismicity structures with threshold magnitudes Mt of 4.4 and 4.6, respectively, have been formed prior to two large earthquakes (on August 17, 1991, Mw = 7.1 and April 25, 1992, Mw = 7.2). Note that, unlike many other subduction zones, deep ring-shaped structures (h = 34–70 km) have not been observed here. At the same time, deep seismicity strips are sometimes formed in this zone. Two new ring-shaped structures with Mt equal to 5.0 and 5.2, which began to form here since 1973, are distinguished. There are grounds to suppose that large earthquakes can be expected in the regions of these structures. We estimate the magnitudes of possible large earthquakes: Mw = 7.8 and 7.9 on the basis of the correlation dependences of the seismicity ring sizes and Mt values on the magnitudes of major events obtained earlier for the East Pacific. These data allowed us to conclude that processes of preparation for a great earthquake with Mw ~ 9.0, similar to the 1700 event, did not begin in the subduction zone. At the same time, a large earthquake (Mw = 7.9 ± 0.1) is possible in a few years in the region of Vancouver Island. We suppose that the formation of shallow rings and deep strips of seismicity is related to deep fluid migration, as occurs in other regions.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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 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".