Apparent Source Spectra for Earthquakes in the Charlevoix Seismic Zone: A Comparison of Direct and Empirical Green's Function Methods
Bibliographic record
Abstract
Two methods of determining the apparent source spectrum of ground motion are compared for small to moderate earthquakes in the Charlevoix Seismic Zone. The first of these methods uses empirical Green9s functions (EGF), in which the spectrum of a target mainshock event is divided by the spectrum of a smaller event in the same location. The EGF approach removes the path, site, and instrument effects from the recorded motion by dividing them out, leaving only the source spectrum of the mainshock. The second method estimates the Fourier spectrum of acceleration near the source directly, by dividing the recorded mainshock spectra by the transfer functions representing the effects of instrument response, attenuation (path effects), and site effects. The results of this study indicate agreement between the direct method and the EGF method. The EGF method is more limited in frequency range by the signal-to-noise ratios than is the direct method. In this study the frequency range was 0.5–10 Hz for the direct method, compared with 1.2–10 Hz for the EGF method. The apparent source spectra are generally well represented by a simple Brune point source model of the radiation. Mainshock events had moment magnitudes ranging from 2.4 to 3.7, with Brune model stress drops in the range from 1 to 80 bars.
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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 | 0.002 | 0.009 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.004 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".