Rate of slip from multiple Quaternary dating methods and paleoseismic investigations along the Talas-Fergana Fault: tectonic implications for the Tien-Shan Range

The ~400 km-long Talas-Fergana fault (TFF) 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 TFF. 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/yr. This rate is higher than the geodetic measurements, but the discrepancy can be partly explained if the TFF accommodates shortening by counterclockwise rotation around a vertical axis. Paleo-earthquakes identified by trenching indicate that at least two primary surface ruptures (and possibly a third) occurred in the past 3800 years, and that no large earthquake has ruptured the Kyldau segment since at least 420 years BP (possibly within the last 2700 years), making this fault segment a potential candidate to generate an earthquake with M>7 in the near future