Long‐Lived Aftershocks in the New Madrid seismic Zone and the Rest of Stable North America
Bibliographic record
Abstract
Abstract Seismicity in the New Madrid seismic zone and the rest of stable North America remains controversial. Some workers view present‐day earthquakes there as long‐lived aftershocks; others view them as background seismicity concentrated in lithospheric weak zones. Separating long‐lived aftershocks from background seismicity, however, is challenging. Here, we used the nearest‐neighbor (NN) method to identify long‐lived aftershocks. The NN method calculates the distances between pairs of earthquakes in a space‐time‐magnitude domain. If the distances are too close to be expected for independent background events that follow the Gutenberg‐Richter law and Poisson distribution, the pairs are taken as clustered events (i.e., the later one in a pair is an aftershock of the earlier one). Our results suggest that, depending on the size and location of the 1811–1812 New Madrid mainshocks, 10.7%–65.0% of the M ≥ 2.5 earthquakes in the New Marid region between 1980 and 2016 may be long‐lived aftershocks. Similarly, considerable present‐day earthquakes in South Carolina are long‐lived aftershocks of the 1886 Charleston earthquake, but the contemporary seismicity in Charlevoix, Québec is predominately background seismicity. These results suggest that present‐day seismicity in stable North America, and perhaps other stable continents, includes both background seismicity and long‐lived aftershocks. Distinguishing aftershocks from background seismicity can be important for hazard assessment.
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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".