Fresnel zones and the power of stacking used in the preparation of data for AVO analysis John C. Bancroft, and Shuang Sun, CREWES/University of Calgary Summary
Bibliographic record
Abstract
The concept of a generalized prestack Fresnel zone is presented to aid in defining a prestack migration aperture for AVO analysis. A large migration aperture requires prestack amplitude scaling that may introduce anomalous results in areas where the acquisition geometry varies. Limiting the prestack migration aperture to the area of specula reflection energy allows the data to be summed into a prestack migration gather and then divided by the fold to balance the amplitudes. The size of the offset Fresnel zone is based on the zero-offset case and represents that portion of the migration operator that sums across a half wavelength of the reflector. In the offset case, that diffraction shape is defined by the double-square-root equation. In the prestack volume (x, h, t) the Fresnel zone can be illustrated by the intersection between the hyperbolic plane of the reflection energy, and the surface defined by the double-square-root equation. Examples show the results of limited aperture gathering on modelled and real data for horizontal events.
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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 | 0.003 | 0.008 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.003 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".