Late Pleistocene left-lateral slip rates of the Gulang Fault and its tectonic implications in eastern Qilian Shan (NE Tibetan Plateau), China

The late Pleistocene deformation pattern in the eastern Qilian Shan remains controversial. Study of the geometry and slip rate of the fault holds crucial value for better understanding the regional deformation pattern. The active E-W trending Gulang and Tianjing Shan Fault Zone is located in the southern boundary of the Tengger Desert which plays a significant role in tectonic deformation and slip transfer in the NE Tibetan Plateau. Geomorphic mapping of the active fault traces reveal that the Gulang fault is composed of two segments, separated by the Guanjia Tai pull-apart basin. Offset geomorphic features indicate that the Gulang fault appears to be primarily sinistral strike-slip with no reverse component. Based on offset gullies/terraces and optically stimulated luminescence dating of offset-related sediments, we obtain a consistent late Pleistocene slip rate of ~2.5 mm/a along the western and eastern segments of the Gulang Fault. Meanwhile, the slip vectors indicate the Gulang fault redistributes strain and transforms displacement along the Haiyuan fault, accommodating the westward motion of the Gobi-Alashan block. Moreover, a devastating earthquake of Ms 8.0 struck Gulang on 23rd May 1927. Geomorphically fresh fault scarps and surface rupture zone are observed at Gulang Fault, we modify the Modified Mercalli Intensities (MMI) and revise the isoseismal map for the Gulang earthquake. Combining with the high-resolution deep seismic-reflection data, the Gulang fault may be the source of the earthquake. Regionally, GPS velocities indicate that faulting, crustal shortening, and basin/block rotation accommodate deformation of the plateau's northern margin. In conclusion, the fault geometry, kinematics, and regional GPS velocities reflect that this region experiences eastward movement of the northeastern Tibetan Plateau relative to the Gobi-Alashan.