Western Quebec seismic zone (Canada): Clustered, midcrustal seismicity along a Mesozoic hot spot track
Bibliographic record
Abstract
The western Quebec seismic zone (WQSZ) is a 160‐km‐wide band of intraplate seismicity extending 500 km from the Adirondack Highlands (United States) to the Laurentian uplands (Canada). Previous authors have proposed that the WQSZ is localized over the Mesozoic track of the Great Meteor hot spot. Here we explore this hypothesis further by investigating regional seismicity characteristics. Focal mechanisms for WQSZ earthquakes, including a new mechanism for a moderate (mN 4.5) earthquake, reveal a pattern of reverse‐sense faulting with SW trending P axes changing to E‐W in the southern part of the zone. We introduce a simple box‐counting method to delineate spatial clusters, based on exceedance of random seismicity density. Combining this approach with focal depths from regional depth phase analysis, we find that seismicity with shallow focus (0–7 km) is characterized by a random spatial distribution, whereas earthquakes with an intermediate focal depth (8–18 km) are strongly clustered along a diffuse linear band trending N50°W. Earthquakes deeper than 18 km are confined to a few distinct clusters. These clusters are characterized by differing b values and, for at least one cluster, repeating events. Projection of hypocenters onto a deep seismic profile and comparison with preexisting crustal structures suggest that local reactivation of Precambrian structural features may have occurred; however, the Great Meteor hot spot track remains the only compelling explanation for the overall distribution of earthquakes. Proximity of seismicity clusters to historic and prehistoric earthquakes lends support to the hypothesis that modern seismicity may represent exceptionally long‐lived aftershocks of large past events.
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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 | 0.003 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.006 | 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".