Spatial Changes in Late Quaternary Slip Rates Along the Gyaring Co Fault: Implications for Strain Partitioning and Deformation Modes in Central Tibet

Studying the slip rate along major strike-slip faults is critical to understanding the deformation and kinematics in continental collision zones. The Gyaring Co fault was previously regarded as a segment of the southern boundary of eastward extrusion in central Tibet, and its eastern segment was linked to the Xainza rift. However, the spatial distribution of its slip rates is poorly constrained, which limits our knowledge about how deformation is partitioned between strike-slip and normal faults in central Tibet. Here, we used optically stimulated luminescence dating to determine the ages of displaced landforms (alluvial fans, lake shorelines, and river terraces) along the Gyaring Co fault. The results demonstrate a southeastward decrease in the late Quaternary slip rate from 2-3 mm/yr to 0.5-1.0 mm/yr over a distance of similar to 130 km. Although the slip rate of the middle-west segment of the Gyaring Co fault seems to have decreased slightly (20%) at similar to 10 ka, it remained relatively stable during the late Quaternary. Regional analysis suggested that the Gyaring Co fault is kinematically compatible with the Xainza rift and probably has accelerated rift extension in its northern part since the middle Miocene. This northward-increasing extension rate may accommodate more than half of the observed strain-rate gradient along the Gyaring Co fault. The difference observed in strain rate requires a strain of similar to 1 x 10(-8) per year, comparable with the average present-day strain rate of the Tibetan Plateau. The Gyaring Co fault separates the crustal blocks that are also deforming internally, suggesting distributed deformation in central Tibet.