Holocene seismogenic faults along the Tanggula-Lhasa section of the Qinghai-Tibet Railway, China
Wu Z H, Wu Z H,Hu D G,Zhao X T, Ye P S,Jiang W. 1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081,China; 2. Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Surface investigation shows that there are five major Holocene seismogenic fault zones along the Tanggula-Lhasa section of the Qinghai-Tibet Railway in the central Tibetan Plateau; from north to south they are the western Wenquan basin marginal fault zone, northern Amdo basin marginal fault zone, Bong Co fault zone, western Golug basin marginal fault zone and Damxung-Yangbajain fault zone. The tectono-geomorphological and chronological analyses indicate that: the western Wenquan marginal fault and northern Amdo basin marginal fault zone in the north are less active, with an average rate of vertical movement of 0.2-0.5 mm/a; the rates of Holocene vertical movements of the western Golug basin marginal fault zone and Damxung-Yangbajain fault zone on the south were ～1.5±0.5 mm/a; and the Bong Co strike-slip fault zone in the central part was most active with an average strike-slip rate of 11±4.5 mm/a during the Late Quaternary. The average vertical slip rate is 1～2mm/a along the normal fault. Based on paleo-seismic evidences, Three paleo-earthquakes (Ms.7 to 8) occurred in approximately 7.4±0.7 ka BP, 4.5±0.3 ka BP and 2.3±0.2 ka BP are identified, and suggest the recurrence interval of Ms.7～8 earthquake is 2300±700a since 8ka BP and at least 1700±200a since 5ka BP along north-margin fault zone of Damxung-Yangbajain basin. There is a higher probability of occurrence of strong earthquakes in the future in the western Wenquan basin marginal fault zone, northern Amdo basin marginal fault zone, northwestern branch of the Bong Co fault zone and Damxung segment of the Damxung-Yangbajain fault zone.