Fault Geometry and Late Quaternary Kinematics Along the Tieluzi Fault: Implications for Tectonic Deformation and Eastward Expansion of the Tibetan Plateau, China

The Tieluzi Fault is the largest structure in the East Qinling Mountains, and is considered to be the easternmost continuation of the Altyn Tagh-Haiyuan-Qinling Fault System (AHQFS) that allows the eastward extrusion of the Tibetan Plateau and South China Block. We studied the fault geometry and kinematics of the Tieluzi Fault using field investigations, detailed interpretations of high-resolution satellite imagery and digital elevation models, and late Quaternary dating methods. Paleoseismic investigations indicate that the most recent earthquake along the Tieluzi Fault occurred before 1,500–1,300 cal. BP. Geological and geomorphological observations show that segments west of Lushi County are more active than those to the east. The spatial variations in tectonic activity along the Tieluzi Fault are interpreted to be related to four possible mechanisms: strike change, discontinuity, intersection, and branch. The late Quaternary left-lateral slip rate is determined to be 0.9 ± 0.1 mm/yr on the Tieluzi Fault. The prominent left-lateral faulting along the Tieluzi Fault suggests that most of the left-lateral displacement along the eastern AHQFS has been accommodated by the Tieluzi Fault, which forms the most frontier of the eastward expansion of the Tibetan Plateau. Furthermore, we suggest that the left-lateral faulting in the East Qinling Mountains is a response to relative eastward motion of the South China block pushed by the Tibetan Plateau with respect to the North China Plain Block. Also, our results indicate that the Tibetan Plateau has undergone a stepwise eastward expansion.