Smooth velocity model from traveltime tomography of an offshore dense wide-angle profile in Nova Scotia: preliminary results
Bibliographic record
Abstract
Understanding the mechanisms that generate rifted continental margins is important in several aspects: (1) scientific - how continents break apart; (2) geopolitical -delimitation of the territorial sea through the United Nations Convention on the Law of the Sea (UNCLOS, United Nations Convention on the Law of the Sea) and; (3) economic, de-risking of oil and gas exploration. The goal of the work proposed here is to prestack migrate in a joint fashion the OETR-2009 OBS and NovaSpan 2000 MCS data. To the best of our knowledge, this would be the first attempt to carry out this type of data analysis and we anticipate significant improvements in the imaging with this approach, in particular of the crystalline basement, crust and the Moho. In order to construct an accurate and detailed but smooth velocity model needed for joint prestack migration of the OBS and MCS data, we will first run a detailed tomographic inversion of the OETR profile. The proposed work will show how velocity modeling of detailed wide-angle refraction observations (such as the OETR profile) can significantly improve the definition of the lower (deep) sediment and basement geometries. We also hope that our results will have a major impact on the sighting of future 3D reflection surveys and exploration wells. The preliminary result of smooth velocity model shows: the depth of the Moho discontinuity is estimated to be ~33 km in the continental crust over a distance of ~60 km, rapidly rising to ~24 km at the distance of ~100 km and, gradually, rising to ~13 km at 280 km within the oceanic crustal domain, with the same depth extending until the end of the model. Between 10-80 km distance, a LVL– HVL–LVL (LVL=Low Velocity Layer, HVL=High Velocity Layer) sequence is observed. In the OCT, between 200-260 km distance, there is a section above the Moho which has a strong gradient and high velocity in compared to normal crust velocities.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".