Quantification of the late Quaternary throw rates along the Yadong rift, southern Tibet

Southern Tibet is characterized by seven main N-S trending rifts bounded by normal faults which accommodate E-W extension. Quantifying the throw and extension rates along these rifts is essential to understand their activity, onset timing, regional seismic hazard and kinematic role in the tectonic evolution of the Tibetan Plateau. The Yadong-Gulu rift (YGR), near Lhasa, is the longest and most prominent rift in southern Tibet, and one of the few that crosses the Himalayas, however it remains poorly studied and understood. Here, we focus on the Yadong rift, i.e., the southern section of the YGR, south of the Yarlung Zangbo suture. We determine the late Quaternary/Holocene throw rates at four sites, where the active Yadong normal fault vertically offsets glacial and fluvial geomorphic surfaces. Using terrestrial LiDAR, UAV and kinematic GPS, we precisely measured vertical offsets (up to 17 m) and constrained the age of abandoned surfaces using 32 10Be cosmogenic surface-exposure ages (~10–20 ka), one optically stimulated luminescence age and two travertine samples dated using U-series dating. The offset-age reconstructions yield uniform throw rates of 0.9 ± 0.3 mm/yr along the entire Yadong rift. Taking a fault dip of 50° as measured in the field, we obtain late Quaternary E-W extension rates of 0.8 ± 0.3 mm/yr, which is similar to but at the lower end of those along other rifts in southern Tibet (~1–2 mm/yr). •Late Quaternary throw rates are uniform all along the rift at 0.9 ± 0.3 mm/yr.•Extension rate is 0.8 ± 0.3 mm/yr (dip of 50°), slightly lower than along other rifts.•No vertical offsets >17 m exist along the entire rift due to climatic reasons.•Seismic hazard exists in the Yadong rift, especially in the Pagri graben.