<i>V</i><sub>p</sub>/<i>V</i><sub>s</sub> Anisotropy and Implications for Crustal Composition Identification and Earthquake Prediction
Bibliographic record
Abstract
Abstract: The ratio of P‐ to S‐wave velocities ( V p / V s ) is regarded as one of the most diagnostic properties of natural rocks. It has been used as a discriminant of composition for the continental crust and provides valuable constraints on its formation and evolution processes. Furthermore, the spatial and temporal changes in V p / V s before and after earthquakes are probably the most promising avenue to understanding the source mechanics and possibly predicting earthquakes. Here we calibrate the variations in V p / V s in dry, anisotropic crustal rocks and provide a set of basic information for the interpretation of future seismic data from the Wenchuan earthquake Fault zone Scientific Drilling (WFSD) project and other surveys. V p / V s is a constant (Φ 0 ) for an isotropic rock. However, most of crustal rocks are anisotropic due to lattice‐preferred orientations of anisotropic minerals (e.g., mica, amphibole, plagioclase and pyroxene) and cracks as well as thin compositional layering. The V p / V s ratio of an anisotropic rock measured along a selected pair of propagation‐vibration directions is an apparent value (Φ ij ) that is significantly different from the value for its isotropic counterpart (Φ 0 ). The usefulness of apparent V p / V s ratios as a diagnostic of crustal composition depends largely on rock seismic anisotropy. A 5% of P‐ and S‐wave velocity anisotropy is sufficient to make it impossible to determine the crustal composition using the conventional criteria ( V p / V s ≤1.756 for felsic rocks, 1.756< V p / V s ≤1.809 for intermediate rocks, 1.809< V p / V s ≤1.944 for mafic rocks, and V p / V s >1.944 fluid‐filled porous/fractured or partially molten rocks) if the information about the wave propagation‐polarization directions with respect to the tectonic framework is unknown. However, the variations in V p / V s measured from borehole seismic experiments can be readily interpreted according to the orientations of the ray path and the polarization of the shear waves with respect to the present‐day principal stress directions (i.e., the orientation of cracks) and the frozen fabric (i.e., foliation and lineation).
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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 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".