Development Characteristics And Hazard Assessment Of Landslide In The Eastern Himalayan Syntaxis Region Of Tibetan Plateau

The eastern Himalayan syntaxis,located in the southeastern Tibetan Plateau,is one of the most tectonic active and fastest uplifting regions on earth.With the rapid uplift of the crust,associated with a variety activities of erosion and surface incision,the current characteristics of the alpine gorge landscape was formed.Under the coupling effect mechanism of endogenic and exogenic geological processes,the geological disasters are extremely developed,not only with varities of types,but also with extremely damage,which caused serious challenge to the planning and construction of highway,railway and hydropower project in this area.Based on the summary of the previous geological hazard data,combined with landslide remote sensing interpretation and field investigation,we analyzed the developing characteristics and distribution rules of landslide in the eastern Himalayan syntaxis region,and conducted landslide susceptibility assessment and seismic landslide hazard estimation,etc.The following results can be obtained:(1)The Tibetan Plateau uplifting,complex folding and faulting of the region,coupled with river incision formed individual topographic,geomorphic and tectonic conditions which create favorable conditions for the preparation of the landslides.The landslides distributed mainly along the Yarlung Zangbo River,the Parlung Zangbo River and the Layue River,and had a densely distribution in rapid exhumation zone.The periodic characteristics of landslide activity had an close relation to the seismic activity and climate fluctuations.(2)Based on the analysis of the geological background and the detailed investigation of development characteristics of the Jaobunong landslide in Lulang,the evolution process of Jaobunong landslide has gone through four stages:the initial deformation stage of the unloading structure of the valley?the disintegration of the rock mass in slope body?vibration cracking and damage stage?landslide blocking and self-stabilization stage.The instability process of the landslide is reconstructed by the dynamic discrete element numerical simulation,which is of great significance to understand the giant landslide mechanism in the study area.(3)By the analysis of the relevant factors of landslide correlation in the study area,the landslide susceptibility evaluation method of AHP-information value method and logistic regression-information value method are proposed,and eight influencing factors including the lithology,slope,aspect,slope,elevation and fault,rivers and roads were selected to assess the landslide susceptibility of the eastern Himalayan tectonic syntaxis.Through validation and sensitivity analysis of each influencing factor,we concluded that the results of the susceptibility mapping are not only related to the evaluation model,but also related to the type and quantity of the selected evaluation factors.Finally,the evaluation results are divided into four regions with extremely high,high,medium and low,which accurately reflect the distribution of the landslide in the study area.(4)As one of the world's well-known earthquake-prone region,where earthquake-induced geological disasters are the main restricting factors of the planning and construction of major projects,as well as the prevention and mitigation of disasters.Seismic landslide hazard map of the eastern Himalayan syntaxis region has been produced for the first time by means of using Newmark method with 10%PGA exceedance probabilities in the future 50 years considering the influence of river erosion,active faults and seismic amplification.The results of produced seismic landslide hazard map showed that the areas with very high seismic landslide hazard are mainly distributed in steep slopes along the drainages and the glacier horns and ridges on Nyenchen Tanglha mountains,Himalayas mountains and Gangrigabu mountains.The areas proned to high and moderate seismic landslide hazard are mainly distributed in the slopes under the glacier horns and ridges as well as relatively high slopes along the faults and drainages.Most areas with relatively flat slopes fall into low seismic landslide hazard zones.According to the produced the seismic landslide hazard results,we analyzed landslide-debris flow dams along the section of Yarlung Zangbo River from Zhibai to Zhaqu,and further discussed the seismic landslide-debris flow dams hazard with 2%exceedance probabilities in 50 years.