Spatial variation of nearly NS-trending normal faulting in the southern Yadong-Gulu rift, Tibet: New constraints from the Chongba Yumtso fault, Duoqing Co graben

Abstract

The Yadong-Gulu rift is the largest active rift within the southern Tibet Plateau. Although tectonic characteristics and geodynamic implications of normal faulting have been widely discussed, precise constraints on the fault slip rates and their spatial distribution are still scarce to date, hindering full exploration of the deformation mechanism of active rifts in the southern Tibet. In this study, we integrated the interpretations of high-resolution satellites and unmanned aerial vehicle (UAV)-acquired images, and topography with the results of field surveys and radiocarbon dating to demonstrate the slip distribution along the Chongba Yumtso fault (CYF) bounding the northeastern sector of the Duoqing Co graben and then discussed their implications for the seismic risk and regional deformation. Since the late Pleistocene, the vertical slip rate and extension rate across the CYF are about 1.2 ± 0.1 and 1.7 (+0.7/−0.5) mm/a, respectively, and the average extension rate across the Yadong-Gulu rift zone is about 2.1 (+0.5/−0.6). According to the activity rate, plane size, basin-mountain height difference, and sediment thickness of the grabens in the southern segment of the rift zone, it is considered that the extension of the main boundary normal fault in the southern segment of the rift has the spatial variation characteristics of decreasing from south to north. According to the comparison of the total extension rate on different time scales, it is considered that the total extension rate of the rift zone in southern Tibet is approximately stable in different time periods, which is ~16 (+5/−4) mm/a. According to the active rate and historical seismic records of the Duoqing Co graben in the Yadong-Gulu Rift Valley, it is considered that the CYF has potential to produce earthquakes with Mw 6.6–7.4.