Oceanic crustal velocities from laboratory and logging measurements of Integrated Ocean Drilling Program Hole 1256D
Bibliographic record
Abstract
Drilling and logging of Integrated Ocean Drilling Program (IODP) Hole 1256D have provided a unique opportunity for systematically studying a fundamental problem in marine geophysics: What influences the seismic structure of oceanic crust, porosity or composition? Compressional wave velocities ( V p ) logged in open hole or from regional refraction measurements integrate both the host rock and cracks in the crust. To determine the influence of cracks on V p at several scales, we first need an accurate ground truth in the form of laboratory V p on crack‐free, or nearly crack‐free samples. We measured V p on 46 water‐saturated samples at in situ pressures to determine the baseline velocities of the host rock. These new results match or exceed V p logs throughout most of the hole, especially in the lower dikes and gabbros, where porosities are low. In contrast, samples measured at sea under ambient laboratory conditions, had consistently lower V p than the V p logs, even after correction to in situ pressures. Crack‐free V p calculated from simple models of logging and laboratory porosity data for different lithologies and facies suggest that crustal velocities in the lavas and upper dikes are controlled by porosity. In particular, the models demonstrate significant large‐scale porosity in the lavas, especially in the sections identified as fractured flows and breccias. However, crustal velocities in the lower dikes and gabbros are increasingly controlled by petrology as the layer 2‐3 boundary is approached.
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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 | 0.000 | 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 | 0.000 | 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 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".