Slip rates based on high-resolution topographic data and multiple Quaternary dating methods along the Talas-Fergana Fault (Kyrgyzstan).

In central Tien Shan, the largest intracontinental strike-slip fault is the northwest trending Karatau-Talas-Fergana Fault (TFF), which 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. First, we used high-resolution satellite imagery (Pleiades and Worldview) to generate a first detailed analysis of the fault segmentation. Detailed mapping reveals numerous offsets in streams, rivers, moraines and abandoned alluvial surfaces along the TFF. We identified nine geometric segments based on strike variations for the TFF. In addition, absence of Quaternary surface ruptures associated with recent faulting leads us to propose that, in its southern part, the Arpa Basin presently marks the southern termination of the active TFF in a horsetail thrust fault system.

Along three segments of the TFF, high-resolution topographic data, derived from photogrammetry using Pleaides, SPOT 6/7 and drone images, allow revealing clear evidence of recent faulting and to determine offsets. Through morphological analyses of offset alluvial surfaces and the application of multiple dating methods (¹⁰Be, ²⁶Al, ³⁶Cl, luminescence and radiocarbon), this study shows that it is informative to have an exhaustive, detailed, and direct comparison between dating methods. Then, we calculate late Quaternary slip rates ranging from 0.8 to 6.3 mm/yr, which vary along strike. Moreover, these rates are higher than the geodetic measurements, but the discrepancy can be partly explained if the TFF accommodates shortening by counterclockwise rotation around a vertical axis.