Crustal Velocity Variations and Constraints on Material Properties in the Charlevoix Seismic Zone, Eastern Canada
Bibliographic record
Abstract
Abstract Crustal velocity variation within impact‐related seismic zones is commonly attributed to factors such as the presence of dense fracture networks, fluid pressure change, and compositional variations. In this study, we combine seismic tomography, rock physics analysis, and gravity anomaly modeling to quantitatively investigate the mechanisms that influence crustal velocity heterogeneities in the Charlevoix Seismic Zone (CSZ), the most active seismic zone in eastern Canada. Earthquakes in the CSZ align in two broad NE‐SW trending clusters, possibly due to the reactivation of St. Lawrence paleorift faults. Within the meteorite impact structure, earthquakes are diffusely distributed, and ubiquitous lower velocity volumes have been attributed to crustal damage from tectonic inheritance exacerbated by the meteorite impact. The Bouguer gravity anomaly contrast across the St. Lawrence River is due to density disparities between the Grenville Province on the north shore and the Appalachians on the south shore. We find a higher velocity region northeast of the impact structure that does not exhibit an observable gravity anomaly, which suggests the co‐existence of rock types of comparable densities but different elastic moduli (e.g., anorthosite and charnockite). Outside the impact structure, compositional variations control velocity changes, whereas inside the impact structure, velocity variations can be explained by porosity enhancement of up to 10% by low (0.1) aspect‐ratio cracks. Our results suggest that intense fracturing and compositional alteration, rather than pore pressure change, have the primary control on seismic velocity variations, and consequently, earthquake processes in the CSZ.
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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 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 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".