Depth-dependent inversion of normal faults: Structural analysis of the Penobscot 3D seismic volume, offshore Nova Scotia
Bibliographic record
Abstract
The inversion of rift-related faults on passive margins through kinematic reactivation is documented globally. Such structures form an integral part in petroleum systems, provide essential constraints on the kinematic and structural evolution of rifts and passive margins, and can be used as global markers for far-field stresses. Despite the importance of inverted normal faults, the controls on their kinematic evolution, as well as existence and interactions within fault populations are often poorly constrained. Here, we present new structural interpretation and kinematic modelling of an inverted relay ramp structure located offshore Nova Scotia, Canada. This structure is imaged on the Penobscot 3D seismic reflection survey down to ~3.5 s TWTT, and is constrained by two exploration wells. We map two major normal faults that display evidence for inversion in their lower portions (reverse faulting and low-amplitude folding), below ~2.5 s TWTT, though retain a normal offset in upper sections. The wider fault population is dominated by ~ENE-WSW striking normal faults that dip both north and south, while both of the two major faults dip approximately south and are associated with antithetic and synthetic faults. This kinematic dichotomy along the major faults is important as inversion such as this may go unrecognised if seismic data does not image the full depth of a structure. To accommodate such depth-dependent inversion, if both horizons co-existed during inversion, a reduction in volume of the sedimentary package is required between the normal and reverse segments of the fault. In this study, we explore possible kinematic mechanisms to explain inversion structure and the mechanisms accommodating the volumetric changes/ or mass movements required using fault restoration and strain modelling. Our results favour a poly-phase deformation history that can be reconciled with other inversion structures on related passive-margin segments, suggesting these could be widespread processes.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 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".