Late Quaternary left-slip rate of the Dangjiang segment along the Ganzi-Yushu-Xianshuihe Fault Zone in the central Tibetan Plateau and the tectonic implications

Abstract

The Dangjiang segment, as the northwestern extremity of the NW-NNW-trending sinistral-slip Ganzi-Yushu-Xianshuihe Fault Zone (GYXFZ) in the central Tibetan Plateau, plays an important role in absorbing strain and regulating the relative movement between active blocks of the Tibetan Plateau interior. However, the late Quaternary strike-slip rate of the Dangjiang segment has rarely been studied because of extreme weather and hypoxia in high-altitude areas (H > 5000 m) and inconvenient transportation, which directly affects the scientific understanding of the tectonic deformation style and reasonable assessment of the strong earthquake hazard along the GYXFZ and the analysis of the present deformation characteristics and geodynamic process of the plateau. Therefore, this study investigated the active tectonics of the Dangjiang segment based on integrated data from high-resolution satellite interpretation, large-scale geomorphic and geological mapping, trench excavations, and Quaternary chronological dating. The results reveal that the Dangjiang segment branches into the main Dangjiang Fault and secondary Zhiduo Fault, both of which have experienced intensive left-strike slip with minor dip movement since the late Quaternary. By measuring offset tributary terraces of the Tongtian River using a UAV survey, and dating their abandonment age using OSL and 14C with the upper terrace model, the late Quaternary strike-slip rate of the Dangjiang Fault and the Zhiduo Fault were estimated at ∼6.9 ± 0.1 mm/a and ∼2.1 ± 0.2 mm/a, respectively. Both the linear fitting value and the slip decomposition model indicate that the strike-slip rate of ∼8–10 mm/a in the late Quaternary is more consistent with geological and geomorphic estimations as well as geodetic constraints along the GYXFZ, and that the late Quaternary slip rate (∼8–10 mm/a) is consistent with the long-term and average slip rates along the structure. This spatiotemporal variation suggests that the current tectonic deformation of the Tibetan Plateau interior may have been continuous and distributed.