Institute of Geomechanics,Chinese Academy of Geological Sciences
Numerous large earthquakes have occurred in the Tibetan Plateau since the recent decades years, which has attracted widespread attention from scholars both domestically and internationally. However, there are some large-scale fault zones on the plateau, which not only have strong late Quaternary activity, but also have the tectonic conditions for generating strong earthquakes. The Karakorum fault is a large dextral strike-slip fault in the western part of the Tibetan Plateau, with the southern part of the Longmucuo Fault being the more active segment. The Perlan Ms 7.0 earthquake occurred in 1883 along this fault. It is helpful to understand the latest deformation behavior of the fault and analyze its seismogenic behavior by identifying the segmented activity characteristics of the fault and surface rupture. Based on high-resolution remote sensing image interpretation and field geological survey, the late Quaternary segmented activity of the southern section of the Karakorum fault and the Chaxikang surface rupture zone are studied in detail. The results show that the southern section of the fault can be divided into three primary segments: Ladakh-Chaxikang, Kunsha-Bar and Menshi-Gongzhu Co segment, which are respectively characterized by dextral strike-slip, dextral strike-slip tension and dextral strike-slip with with a horsetail normal fault. The minimum horizontal displacement measured at the surface rupture zone is 8-9m. Combined with the rupture length of ~200km, the magnitude of the earthquake is estimated to be ~7.5. The Karakorum fault zone, which regulates the material extrusion in the western plateau, gradually transforms from a rigid block migration mode in the northwest section to a more dispersed arc-shaped normal fault and strike slip deformation in the southeast section.