Active transform faults in the Gulf of Guinea: insights from geophysical data and implications for seismic hazard assessment
Bibliographic record
Abstract
The seismotectonics of Western Africa show the occurrence of major earthquakes (e.g., 1636 southwestern Ghana, 1855 offshore Monrovia, 1939 offshore Accra, and 1983 Gaoual-Guinea) and prominent offshore transform faults. However, there is no analysis that links the continental active tectonics with the oceanic fault zones of the Gulf of Guinea. We study the active tectonics by firstly mapping the main transform faults using a combination of bathymetric, gravimetric, and magnetic data. The data analysis associates regional seismicity (historical and instrumental) with focal mechanisms as extracted from the recently published seismotectonic map of Africa. We identify active transform faults, the Chain (CFZ), Romanche (RFZ), Saint Paul (SPFZ), and Arkhangelskiy (AFZ) fault zones. We also calculate strain rates on these faults from Late Cretaceous (–85 Ma) to present time using paleomagnetic data and infer slip rates from the seismic moment data. The strain rates show a first stable trend around 2 cm/year and then accelerate to 4 cm/year in the last 10 million years. The comparison of Late Quaternary strain rates with geodetic strain rates shows an accumulation of seismic energy that could lead to the initiation of an Mw 7–7.5 earthquakes on the Saint Paul transform fault. Our seismotectonic analysis clearly links oceanic and continental tectonics, with about a 20°–30° anticlockwise fault trend rotation for CFZ, RFZ, and SPFZ. The potential for the occurrence of large earthquakes in the Gulf of Guinea should be taken into account for a realistic regional seismic and tsunami hazard of the Gulf of Guinea.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| 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".