A Revised Magnitude-Recurrence Relation for Shallow Crustal Earthquakes in Southwestern British Columbia: Considering the Relationships between Moment Magnitude and Regional Magnitudes
Bibliographic record
Abstract
An important component of seismic hazard analysis is the magnitude-recurrence relation, which provides the cumulative rate of occurrence of earthquakes within a seismic source zone as a function of magnitude. In the national seismic hazard maps developed for the 2005 National Building Code of Canada, the magnitude-recurrence relation for the Cascade Mountains zone of southwestern British Columbia (casr), the seismic zone in which Vancouver and Victoria are located, is based mainly on earthquakes measured on the local scale M L (Richter scale), but other scales including body-wave magnitude ( m b), coda duration magnitude ( M c), and moment magnitude ( M ) have been used for some of the events. The mixture of magnitude types is a potential source of bias in the relations. By using data from recently calculated regional moment tensor solutions, a local magnitude-moment magnitude relationship is developed for magnitudes of 2.9 < M L < 6.0 in the casr zone. This relation, along with relations from other sources for m b and M c, and specific moment magnitude values where available, are used to develop a homogeneous moment magnitude catalog for use in the formulation of a new casr zone magnitude-recurrence relation. The use of a homogeneous moment magnitude scale produces a significant change in the shape of the magnitude-recurrence curve in the casr zone. Perhaps more importantly, the use of a homogeneous catalog reduces the uncertainty in the recurrence rates of moderate to large earthquakes in casr by nearly an order of magnitude. We conclude that the use of a homogeneous magnitude scale is critical to producing unbiased magnitude-recurrence relations.
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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 | 0.001 | 0.006 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".