Stresses in the subducting slab beneath southwest Japan and relation with plate geometry, tectonic forces, slab dehydration, and damaging earthquakes
Bibliographic record
Abstract
We infer stresses in the subducting slab beneath southwest Japan from focal mechanisms and discuss their geodynamical implications. The majority of the 824 fault plane solutions used in this study were obtained by the Japan Meteorological Agency for earthquakes that occurred during 1970–2002 and were previously unpublished. The focal mechanisms are believed to reflect stresses in both the untransformed slab crust and the slab mantle. The stresses are controlled by tectonic forces, and the earthquakes are facilitated by local dehydration. The slab experiences a regional E–W stretch, that is, downdip and margin‐parallel tension at the Kyushu and Nankai margins, respectively. We propose that the margin‐parallel component of mantle resistance to the obliquely subducting young slab at Nankai provides an easterly stretch, acting against the westerly slab pull of the older and colder part of the slab at northern Kyushu. Despite the complex slab geometry along the Nankai margin the direction of tension is largely parallel with the local strike of the slab, indicating that the slab is a stress guide. The complex slab geometry is not related to the present stress regime but likely reflects severe deformation in the past when an extremely young and incompetent plate was forced to subduct against its own buoyancy. The maximum margin‐parallel stretch and a sharp bending of the slab both occur in the area of the 2001 M 6.7 Geiyo earthquake. Using a simple strength envelope model, we demonstrate that normal‐faulting failure of the slab mantle can occur under such conditions.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".