Response of the tectonically erosive south Peruvian forearc to subduction of the Nazca Ridge: Analysis of three‐dimensional analogue experiments
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Bibliographic record
Abstract
The collision zone of the obliquely subducting Nazca Ridge and the erosive Peruvian forearc is characterized by enhanced tectonic erosion, normal faulting, forearc uplift, and a minor indentation. We apply two three‐dimensional sandbox experiments monitored by an optical particle imaging velocimetry system to decipher the spatial and temporal evolution of forearc deformation. During oblique convergence the rigid model ridge causes a wave of uplift followed by subsidence to shift along the forearc. By varying the strength of the analogue material we demonstrate that the forearc response to ridge subduction, in particular the amount and rate of uplift and wedge indentation, is controlled by the mechanical strength of the forearc. The model using the high‐strength material yields results more compatible with the geological record of the Peruvian forearc. First, the modeled amount of uplift scales to ∼1.2 km in nature, which agrees with ∼1.0 km of uplift recorded by marine terraces. Second, the calibrated model uplift rate of 0.9 km/Myr is similar to the natural rate of ∼0.7 km/Myr. Third, the development of normal faults above the model ridge is in accordance with the style of faulting above the Nazca Ridge. Finally, oversteepening of the uplifted wedge and local slope failure, as observed in the experiment, has also been identified off southern Peru. A comparison between the erosive Peruvian and accretive margins emphasizes that the style of ridge‐induced deformation depends on the forearc strength and crustal structure, which in turn are controlled by the long‐term evolution of the margin's mass transfer regime.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| 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) | 0.000 | 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 it