[S-SS34_29PO1] Active faults and paleoseismology

[SSS34-P28] Systematical deflections and offsets of stream channels along the left-lateral strike-slip Kunlun Fault

*Bing YAN¹, Aiming LIN² (1.Graduate School of Science and Technology, Shizuoka University, 2.Department of Geophysics, Graduate School of Science, Kyoto University)

Keywords:Kunlun Fault, left-lateral strike-slip fault, stream channel, systematical deflection, Tibetan Plateau, eastward extrusion

During the past two decades, the integration of geologic, geomorphic, seismic, and geophysical information has led to increased recognition and understanding of the tectonic significance of geomorphic features caused by strike-slip along active strike-slip faults. Tectonic landforms developed along active strike-slip faults are mainly characterized by systematic deflections and offsets of streams which are regarded as reliable displacement markers useful for reconstructing the long-term activity of active faults. It has been demonstrated that stream offsets have resulted from repeated large strike-slip earthquakes. The study of tectonic geomorphology will provide a new insight into the seismic activity, longevity and structural evolution of active strike-slip faults. The Kunlun Fault is a typical active strike-slip fault zone extends for ~1200 km in the northern Tibetan Plateau that has triggered the 2001 Mw 7.8 Kunlun great earthquake. In this study, we present evidence for the systematical sinistral deflection and/or offset of the stream channels and valleys of the upper Yellow River drainage along the eastern intramontane segment of ~400 km of the fault zone. Topographic analysis of 3D perspective images constructed using Digital Elevation Model (DEM) data, high resolution Google Earth images and 15-m-resolution Landsat Enhanced Thematic Mapper (ETM+) images reveals the following: (i) various amounts of sinistral offset have accumulated on the tributary stream channels, valleys, and gullies of the upper Yellow River; (ii) the eastern intramontane segment of Kunlun fault accumulated sinistral offset amount for at least 12 km; (iii) the linear relationship between the between the accumulated offset amount and the upstream length from the deflected point to valley head of the stream involved can be reliable indicator of long-term slip rate. The findings of this study support that the Kunlun Fault is a left-lateral strike-slip that partitions deformation into the eastward extrusion of the Tibetan Plateau to accommodate the continuing penetration of the Indian plate into the Eurasian plate.