Rate of Slip From Multiple Quaternary Dating Methods and Paleoseismic Investigations Along the Talas‐Fergana Fault: Tectonic Implications for the Tien Shan Range

• Published in: Tectonics (Washington, D.C.) Vol. 38; no. 7; pp. 2477 - 2505
• Main Authors: Rizza, M., Abdrakhmatov, K., Walker, R., Braucher, R., Guillou, V., Carr, A. S., Campbell, G., McKenzie, D., Jackson, J., Aumaître, G., Bourlès, D. L., Keddadouche, K.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-07-2019; American Geophysical Union (AGU)
• Subjects: active faults; Alluvial fans; Beryllium 10; Continental interfaces, environment; cosmogenic dating; Deformation; Earth Sciences; Earthquakes; Environmental Sciences; Fault lines; Geodetic measurements; Geomorphology; Global Changes; Holocene; Identification; Imagery; Kinematics; luminescence dating; Methods; paleoseismology; Quaternary; Radiocarbon dating; Satellite imagery; Sciences of the Universe; Seismic activity; Spaceborne remote sensing; tectonic geomorphology; Tectonics; Tien Shan; Trenching; luminescence dating; tectonic geomorphology; paleoseismology; cosmogenic dating; tien shan; active faults
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2018TC005188

The ~400‐km‐long Talas‐Fergana Fault is one of a series of major right‐lateral strike‐slip faults that cross the Tien Shan Range. This fault has been recognized as active in the late Holocene and accommodates part of the deformation induced by the ongoing Indo‐Asian collision. The kinematics and the role of this strike‐slip fault are poorly understood with no large earthquakes reported in the instrumental or historical catalogs, and no well‐constrained geological slip‐rate estimates. Here we used high‐resolution satellite imagery to present a first detailed analysis of the fault segmentation. We identified nine geometric segments based on strike variations for the Talas‐Fergana Fault. Along the Kyldau segment, through morphological analyses of an offset alluvial fan and the application of multiple dating methods (10Be, 26Al, 36Cl, luminescence, and radiocarbon), we calculated a late Quaternary slip rate ranging from 2.2 to 6.3 mm/year. This rate is higher than the geodetic measurements, but the discrepancy can be partly explained if the Talas‐Fergana Fault accommodates shortening by counterclockwise rotation around a vertical axis. Paleoearthquakes identified by trenching indicate that at least two primary surface ruptures (and possibly a third) occurred in the past 3,800 years, and that no large earthquake has ruptured the Kyldau segment since at least 420 years B.P. (possibly within the last 2,700 years), making this fault segment a potential candidate to generate an earthquake with M > 7 in the near future.
Key Points
The 400‐km‐long Talas‐Fergana Fault (TFF) can be subdivided into nine geometric segments
A first geological slip rate of 2.2–6.3 mm/year is constrained by geochronological dating of an alluvial fan
The TFF may be associated with counterclockwise rotations around a vertical axis. This model reconciles geodetic and geologic slip rates