Inversion of first-arrival seismic traveltimes without rays, implemented on unstructured grids
Bibliographic record
Abstract
We develop a method for inverting first-arrival seismic traveltimes without using ray tracing in the forward solution, nor to calculate sensitivity information. We consider unstructured 2-D triangular and 3-D tetrahedral grids for discretizing the subsurface velocity distribution. Unstructured grids provide some computational advantages when dealing with complicated shapes that are difficult to represent with rectilinear grids. However, we stress that the key details of our inversion approach that avoid ray tracing are equally relevant to rectilinear grids. The forward problem is solved using the Fast Marching Method, an efficient numerical algorithm that can be used for propagating first-arrival seismic wave fronts through a velocity distribution. Our minimum structure inversion algorithm uses sensitivity information calculated directly during the forward solution. This calculation relies on explicit symbolic differentiation of the forward modelling equations and, as such, our inversion approach does not require ray tracing and uses sensitivity information that is numerically consistent with the forward solution. Our method is applied to 2-D and 3-D geologically realistic synthetic scenarios based on the Voisey's Bay massive sulfide deposit in Labrador, Canada.
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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 | 0.000 | 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) | 0.004 | 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".