Investigation into the scattering response of mineral ore deposits in heterogeneous environments by means of two-dimensional and three-dimensional seismic modelling
Bibliographic record
Abstract
The goal of this thesis was to investigate the possibility of directly detecting massive sulphide deposits in hardrock media using seismic methods. Initial numerical modelling has shown that sulphides scatter seismic energy characteristically depending on shape, size and composition; it is suggested that amplitude/phase characteristics can be used to locate and define sulphide orebodies with seismic data. This thesis expands on these results with the improvement of heterogeneous models based on available data to more realistically simulate an orebody embedded in crystalline material. The first part of the project discusses a means of assessing heterogeneity with borehole logs. Analysis of the various lithologies of Sudbury and other impact structures has shown that despite differences in age and morphology, the brecciated basement beneath impact craters is characterized by small scale lengths, as opposed to the large scale lengths often encountered in non-impacted crystalline rocks. The character of seismic profiles is invariably linked to these scale lengths: seismograms range from relatively transparent to highly reflective (noisy), depending on the ratio of seismic wavelength to heterogeneity scale length. This variability is the key to the success or failure of seismic methods in crystalline environments. Elastic finite difference models of scattering media demonstrate the difference between favourable and unfavourable seismic exploration settings: when the ratio of scale length to seismic wavelength is sim;1, large amounts of scattering noise are generated that reduce the signal to noise ratio of surface recorded data. When simple bodies representing sulphide deposits are placed in the heterogeneous models, they are detected provided that (1) the deposit has a large enough impedance contrast, (2) it is larger than the dominant seismic wavelength, and (3) its dimensions are either smaller or greater than the dominant scale of heterogeneity of the host rocks. Deep within a large scale length medium however, travel-time and amplitude fluctuations of a seismic wavefront significantly alter the expected reflected response of the sulphide. Finally, it is demonstrated that based on all available information from the Sudbury structure, sulphide deposits within the footwall will be seismically detectable provided they present a step impedance contrast with host material.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| 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 | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".