Geologic Slip‐Rate Determinations on the Talas‐Fergana Fault: Mismatch With Geodetic Slip Rate

Abstract

AbstractDetailed new paleoseismic field investigations at two sites on the Talas‐Fergana fault, a poorly known strike‐slip structure that transects the Tien Shan mountain range, document late Holocene slip rates of 11–16 mm a−1. This prominent structure is distinctive in striking obliquely NW‐SE across the Tien Shan, which is otherwise dominated by contractional structures striking generally E‐W. Moreover, a satellite‐based Global Positioning System network spanning the Tien Shan orogen records active N‐S contraction rates of ~20 mm a−1, but limits slip on the Talas‐Fergana fault to <2 mm a−1. This profound mismatch between long‐term geologic and short‐term geodetic slip rates, which may suggest temporal variability in slip, highlights the importance of field‐based investigations as a complement to remotely sensed data, particularly in evaluating models of lithosphere behavior and earthquake probabilities on presently locked faults such as the Talas‐Fergana.