Multistage Nucleation of the 2021 Yangbi M<sub>S</sub> 6.4 Earthquake, Yunnan, China and Its Foreshocks
Bibliographic record
Abstract
Abstract On 21 May 2021, an M S 6.4 earthquake occurred in Yangbi, Yunnan province, China. A significant foreshock sequence occurred 3 days before the mainshock, which provides an opportunity to study earthquake nucleation. In this study, we adopt a template matching technique and a double‐difference location method to build a catalog for the foreshock sequence of the 2021 Yangbi M S 6.4 earthquake, which contains 1,086 events with high‐precision locations. The whole foreshock sequence can be grouped into four episodes, each with one M W > 3.7 principal foreshock. The foreshocks within the first episode initiated on a NW‐trending small fault, whereas the subsequent foreshocks within episodes 2–4 jumped onto a nearby major fault to gradually rupture toward NW direction. We identify three M W > 3.4 repeating earthquakes on the NW‐trending small fault in episode 1, implying that aseismic slip occurred in the early stage of the mainshock nucleation. Meanwhile, the rupture dimension estimation and stress disturbance analysis of the later foreshocks in episodes 2–4 reveal a cascading rupture process on the major fault, indicating that stress transfer may dominate the later stage of the mainshock nucleation. Hence, our study suggests that the two end‐member mechanisms of aseismic slip and stress transfer may be compossible in the nucleation process of the 2021 Yangbi M S 6.4 mainshock.
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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 | 0.001 |
| 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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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 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".