Late Quaternary activity of the Zemuhe and Xiaojiang faults in southwest China from geomorphological mapping

Abstract

There has been limited detailed geomorphological research on the Kangding fault system, located along the eastern margin of the Tibetan Plateau, despite the system containing active faults with high slip rates. Fault-related landforms such as offset streams were mapped at selected sites along the Zemuhe and Xiaojiang faults in the central and southern sections of the Kangding fault system. The results permitted assessment of the mode and rate of late Quaternary fault movement based on more comprehensive information than used in previous studies. The left-lateral strike-slip of these faults reflects the large-scale clockwise rotation of the Southern Tibetan Plateau. The estimated strike-slip rate of the Zemuhe fault is ca. 5–9 mm yr − 1 , whereas that of the Xiaojiang fault is ca. 14–22 mm yr − 1 . These rates and the known slip rates of the adjacent faults indicate that, in the northern and southern sections of the Kangding fault system, the regional tectonic stress from the clockwise rotation has been released mainly along the major faults; whereas, the stress in the central section has been released by both fault movement and deformation in surrounding areas. The latter mechanism reflects a more complex geological structure in the central system of distinct thrusts and folds. Late Quaternary vertical deformation along the Zemuhe and Xiaojiang faults has mostly resulted from local stresses associated with strike-slip movement, although the Zemuhe fault has also undergone slow but consistent normal faulting since the early Quaternary due to its orientation oblique to the direction of the clockwise rotation.