Seismic velocities and anisotropy of core samples from the Chinese Continental Scientific Drilling borehole in the Sulu UHP terrane, eastern China
Bibliographic record
Abstract
A detailed study of seismic properties (P and S wave velocities, hysteresis, anisotropy and shear wave splitting) has been carried out on a unique suite of deep borehole core samples from the Chinese Continental Scientific Drilling (CCSD) project, which penetrated 5158 m into the Sulu ultrahigh‐pressure (UHP) metamorphic terrane (China). Seismic velocities of the deep core samples are more and less sensitive to pressure in the low pressure (<200–300 MPa) nonlinear and high pressure (>200–300 MPa) linear regimes, respectively, than samples from the surface. The comparison suggests that the high pressure data from the core samples are much more reliable for extrapolation to deeper crust than the data from surface analogs that have been subjected to long histories of weathering and alteration along intergranular and transgranular cracks. The significant increases in the pressure sensitivity of seismic velocities for the core samples in the nonlinear regime indicate that drilling‐induced and stress‐relief microcracks with small aspect ratios are fresh and clean without secondary mineral in‐fillings, and are thus easy to close completely under the applied hydrostatic pressure conditions of the laboratory. The data also elucidate that the velocity‐pressure data can successfully provide important hints about the preferred orientation of microcracks that causes P wave velocity anisotropy and shear wave splitting in cracked rocks, and that the effect of compression on the Vp/Vsratios is negligible for crack‐free compacted rocks. The seismic velocities of equivalent isotropic (fabric‐free) and crack‐free crystalline aggregates calculated from room pressure single crystal elastic constants using the Voigt average are in good agreement with the laboratory data at ∼200 MPa. Comparison of the seismic reflection image from the vicinity of the borehole with the normal‐incidence reflection coefficient profile computed from the laboratory‐measured velocities and densities infers that the seismic reflections originate from mafic (eclogite and retrograde eclogite) or ultramafic units within dominantly felsic rocks.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 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 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".