Seismic attenuation in the Anahim Volcanic Belt and adjacent regions of British Columbia
Bibliographic record
Abstract
In this study we investigated coda-wave attenuation (Qc) in the interior of British Columbia, with a focus on the Anahim Volcanic Belt (AVB) and specifically the Nazko Cone region using the single scattering approximation on records from short period and broadband stations of the regional Canadian National Seismic Network (CNSN) and POLARIS Network. Our dataset is comprised of 380 earthquakes recorded between 1999 and 2012 with magnitudes ranging from 1.6 to 3.9, depths from 0 to 36 km and epicentral distances of 15 to 100 km. This gives a total of 423 high signal to noise (S/N) traces (S/N?5.0) useful for Qc calculation (with a range of ellipse parameter, a2, of 30 to 110) across the region. Coda windows were selected to start at tc = 2tS (two times the travel time of the direct S wave), and were filtered at center frequencies of 2, 4, 8, 12 and 16 Hz. Although the dataset is relatively small, with substantial uncertainties, a consistent pattern emerges. We find that in the interior of BC, the lowest Q0 values (e.g., Q0 of 39) are in the vicinity of Nazko Cone, near the 2007 earthquake swarm. This sequence of more than 1000 earthquakes occurred at depths of 25-31 km and was interpreted as a magma injection at the base of the crust. Further, we find that all stations within the AVB show lower Q0 values compared to other stations in the BC interior. Averaging all data in the AVB with a2 of 30-50 km (UBRB, MCMB1, SULB, THMB) yields a low average Q0 of 53, compared to an average Q0 of 67 at other stations in the BC interior, and an average Q0 of 70 for stations in the Cascadia subduction zone. Our results showing low Q0 throughout the AVB (and the lowest Q0 at Nazko Cone) provides additional support for the interpretation of magma injection into the lower crust during the Nazko earthquake sequence, fracturing of the crust, and high seismic attenuation.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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 teacher head, 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".