Deciphering the Role of Plate Motion Changes and Inherited Structures in Mega-Transform Fault Development Using Geodynamic Numerical Models
Bibliographic record
Abstract
Transform faults most commonly exhibit offsets of 100 to 200 km, with a minority defined as mega-transforms with >200 km offsets. Consequently, these mega-transforms represent a relatively understudied feature of plate tectonics with our understanding of their formation and development currently incomplete. In this study, we use the numerical modelling software ASPECT (Advanced Solver for Problems in Earth's ConvecTion) to create high resolution 3D simulations of mega-transforms following oblique changes in plate motion. Specifically, we determine how inducing transpression and transtension across a mega-transform fault affects the development of new transforms and mid-ocean ridge segments. Our numerical models all implement an initial stage of orthogonal extension and continental break up along an offset rift, followed by a second stage of oblique extension across a wide range of extension azimuths (-75° to 75°). Here, we find that small transpressional changes in plate motion (-15°) lead to the development of a short 130 km long transform, whilst larger (-75°) changes in plate motion led to the development of a longer 300 km transform. Alternatively, increasingly oblique, transtensional deformation leads to increased rifting between the offset ridges with a >60° change in the extension orientation leading to continental rifting across the old transform margin. These results are analogous to real world examples such as the Davie (West Somali Basin) and Ungava Fault Zones (Davis Strait) where we also highlight the role of plate motion changes on continental cleaving. Additionally, the orientation of mid-ocean ridges and transforms in the Labrador Sea suggests a late phase of E-W extension prior to the cessation of spreading.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".