Earthquake relocations and three-dimensional VP, VS and VP/VS along the fast-slipping Gofar oceanic transform fault, East Pacific Rise.
Bibliographic record
Abstract
Fast-slipping mid-ocean ridge transform faults are characterized by quasi-periodic seismic cycles with typical inter-event times of 5 to 8 years. In particular, the Gofar transform fault (GTF) of the East Pacific Rise, generates a MW ~ 6 earthquake every 5 to 6 years on short (~20 km) along-strike segments separated by a barrier zone. Therefore, the GTF presents the opportunity to investigate the relation between fault structure and material properties of this fault to earthquake processes. Here, we perform a joint inversion of P- and S-wave arrival times from local earthquakes to develop three-dimensional seismic velocity models (VP, VS and VP/VS) of the easternmost and westernmost segments (G1 and G3, respectively). The velocity models reveal that G3 is characterized by a more heterogeneous fault zone velocity structure compared to G1. Sharp velocity contrasts are observed along G3 interpreted to reflect along-strike variations in material properties. G1 is characterized by large low-velocity anomaly extending through the entire oceanic crust with subtle along-strike variations. The 2020 Mw 6.1 earthquake occurred within a low VP, low VS and high VP/VS patch along G1 whereas the 2008 Mw 6 earthquake occurred on sharp VP, VS and VP/VS contrast. We also note similarities between the two fault segments. In particular, rupture barrier zones are characterized by a high rate of seismicity and a rapid decrease following the mainshock. We also note the occurrence of deep seismicity in low VP/VS patches beneath the rupture barrier zones, which may indicate sea-water infiltration at 10 to 14 km depth below sea level.
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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 | 0.000 |
| 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".