Unveiling the Surface Rupture of the 1946 Chatkal Earthquake (Mw 7.5, Tien Shan): Insights from Pleiades, UAV Imagery, and Trenching
Bibliographic record
Abstract
In the central Tien Shan, the Karatau-Talas-Fergana Fault (TFF) is the largest intracontinental strike-slip fault, recognized as active during the late Holocene and accommodates a portion of the deformation resulting from the ongoing Indo-Asian collision. However, the kinematics and role of the TFF remain poorly understood, with no large earthquakes documented in instrumental or historical catalogs. Notably, in the region, the strongest shaking in the 20th century occurred during the November 2, 1946, Chatkal earthquake, but with a potential epicenter located approximately 20 km from the TFF trace. Despite this, there are no clear reports of surface faulting, and no fresh tectonic scarps associated with the 1946 earthquake have been identified along the TFF fault. As a result, the location, focal mechanism, and potential surface rupturing of the 1946 Chatkal earthquake remain debated.In this study, in the Chatkal Range, we utilize high-resolution satellite imagery (Pleiades and Worldview) to conduct a comprehensive analysis of fault segmentation. Our detailed mapping reveals multiple offsets in streams, rivers, moraines, and abandoned alluvial surfaces along the TFF. Additionally, UAV-based digital elevation models (DEMs) and orthophotos provide unprecedented detail of the fault's morphology, allowing us to measure an offset of approximately 4.6 meters for the more recent surface rupture.We also conducted new Quaternary dating of displaced geomorphic markers and excavated a paleoseismic trench, where we discovered a fresh surface rupture. In the trench, two separate surface ruptures were observed, offsetting sedimentary units from a sag pond. We propose that the most recent earthquake event correlates with the 1946 Chatkal earthquake. Based on the trench data, we estimate return times of approximately 3,000–4,500 years and calculate slip rates from the cumulative offsets. By integrating these data, we provide insights into the seismic cycle of the Chatkal segment and propose the 1946 earthquake for the most recent faulting event in the region.
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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 | 0.001 | 0.001 |
| 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".