OSL DATING OF THE LATE QUATERNARY SLIP RATE ON THE GYARING CO FAULT IN CENTRAL TIBET

The Gyaring Co Fault (GCF) is an active right-lateral strike-slip fault in central Tibet that accommodates convergence between India and Asia in the interior of the Tibetan Plateau. The average long-term slip rate of the fault remains controversial, given the absence of absolute age data of faulted geomorphic features. We have applied optically stimulated luminescence (OSL) dating to the northern segment of the GCF, revealing that the GCF has displaced alluvial fans at Aerqingsang by 500 +/- 100 m since their deposition at similar to 109 ka, yielding a slip rate of 4.6 +/- 1.0 mm/yr. A slip rate of 3.4 +/- 0.4 mm/yr is inferred from analysis of an alluvial fan with an offset of 65 +/- 5 m (similar to 19 ka) at Quba site 1. The Holocene slip rate is estimated to be 1.9 +/- 0.3 mm/yr, as inferred from the basal age ((similar to 8.3 ka) of terrace T1 that has a gully displacement of 16 +/- 2 m at Quba site 2. These slip rates are generally lower early estimates (10-20 mm/yr), but are consistent with more recent results (2.2-4.5 mm/yr) and GPS data for other strike-slip faults in this region, indicating that deformation may be distributed across the entire Tibetan Plateau. Moreover, we suggest that the slip rate along the GCF may have decreased slightly during the late Quaternary.