Abstract:The middle south section of Jiali-Chayu fault is located in intensive uplift alpine topography area. Due to the dense vegetation, unclear fault landforms, and lack of Quaternary sediments, which hinder understanding of the geometric distribution of fault and seismicity. Based on the remote sensing interpretation, faulted landforms and soft-sediment deformation structures in Late Quaternary lacustrine, and geophysical section, paleoseismic trench, OSL and 14C dating of sediment, at least two paleoseismic events were revealed with ages between 16.13±1.06~15.66±0.92ka and 8630±600a~9561±37 BP., respectively. According to the geological survey combined with the data available, at least five paleoseismic events since the late Quaternary in the middle-south section of Jiali-Chayu fault, time is 16130~15660a, 11060a, 8630~9561a BP, 2780~2160a BP and 650a BP, and the earthquake recurrence period is about 2000-5000a. GPS data show that the horizontal slip rates of the middle and southeast sections of the Jiali-Chayu fault are 1.3-2.0mm/a and 2-4mm/a, the compression rates are 2.5-2.9mm/a and 5.1-6.2mm/a, both are dextral compression, and there are two faults in north and south. The fault activity is obviously controlled by the eastward escaping of the Tibetan Plateau and clockwise rotation around the eastern Himalayan syntaxis. Jiali-Chayu fault has a characterized by slow strain accumulation and long recurrence interval. Considering that the top of eastern Himalayan syntaxis is still in a high state of structural compression, possibility of an earthquake (M≥7) in the future.
