Study On The Relationship Between The Development Of Large Landslides And The Evolution Of Neotectonic Geomorphology In The Motuhe Section Of The Yarlung Zangbo River

The Meridian section of the Yarlung Zangbo River is located in the Himalayan eastern tectonic knot,spanning the Yarlung Zangbo suture zone,and is the leading edge of the Indian Ocean plate subduction and wedging to the Eurasian plate.It is one of the regions with the strongest geomorphological evolution of tectonic movement on the earth today.It belongs to the "V" type alpine valley in the valley form.Based on the hydropower research topic,based on the large-scale field investigation,combined with the geological environment conditions of the study area,adopting OSL dating and other techniques,using the analysis function of arcgis,the layered geomorphology,large-scale landslide development characteristics and distribution law of the study area.The research was carried out,and the new structural geomorphological evolution characteristics of the study area and adjacent areas were comprehensively analyzed,revealing the relationship between large-scale landslides and geomorphological evolution.The main understandings are as follows:(1)The continuous wedging of the Indian plate since the middle and late Paleogene,the continuous uplift of the Qinghai-Tibet Plateau,and the rapid undercut of the Yarlung Zangbo River have controlled the geomorphological evolution of the study area and adjacent areas.The neotectonic movement in the study area and adjacent areas is strongly uplifted and the strike-slip activity of the fault.The Tertiary discontinuous,uneven and differential uplift of the Qinghai-Xizang Plateau formed a three-level plan(mountain surface,mountain surface,basin surface),and the study area developed two levels of planes: the mountain surface and the basin surface.(2)The multi-level erosion surface developed since the Quaternary in the study area is: the elevation of the stripping surface is 3200 m in the vicinity of the side Xinxiang Township,and it is 2600 m in the downstream back collapse township;the I-level valley shoulder has an elevation range of 2500~2300m;The rank of the valley shoulder,the overall distribution of elevation is 1800~1700m;the grade III valley shoulder has an elevation range of 1400~1200m,and its elevation gradually decreases from the upstream Xinxiang to the downstream back collapse township.After the Qinghai-Tibet Plateau in the Qinghai-Tibet Plateau,the Yarlung Zangbo River formed a wide valley area above the white,and quickly cut down the Yarlung Zangbo River below the straight white to form the alpine valley landscape of the study area.The study area develops 8 terraces,and the T8 tug-of-war height is nearly 523 m,forming an age of 0.1Ma,and its undercut rate can reach 5-6 mm/a.(3)The Yarlung Zangbo River is a turning point near the straight white,and there are obvious differences in the top and bottom valleys.The geological disasters in the upper wide valley area are dominated by debris flows,and the landslides and collapses are scattered.In the lower reaches of the mountain valleys,large landslides and collapses are dominant.The debris flow is less accumulated.Large landslides in the study area are mainly developed in Chayudu.There are 43 large landslides in the study area,including 30 on the left bank and left bank of the Yarlung Zangbo River,accounting for 69.8%,and 13 on the right bank,accounting for 30.2%.The slope of the landslide development is mainly concentrated between 30 and 40°.The ratio of the trailing edge of the landslide sliding source area is mainly distributed in the valley shoulder elevation;the development of the river zoning,the more dense the landslide is developed;the large landslides in the study area are all developed near the fault zone,and the main sliding direction of the large landslide is The fracture zone is nearly vertical.(4)Since the mid-Pleistocene,the acceleration of the study area has led to the transformation of the valley from the wide valley to the canyon.Since the late Pleistocene,the continuous uplift of the Qinghai-Tibet Plateau and the rapid undercut of the Yarlung Zangbo River have resulted in the formation of multi-level valley shoulders and canyons.The strong deep unloading and sloped landforms provide boundary conditions and geomorphological conditions for the landslide.The uplift of the Qinghai-Tibet Plateau provides internal dynamic geological effects for the development of landslides;the alpine gorge geomorphology of the Yarlung Zangbo River provides favorable topographic and geomorphic conditions for the development of large-scale landslides;under the control of comprehensive conditions such as dynamic conditions,boundary conditions and geomorphological conditions,the study Large landslides in the area are very developed.The development of large-scale landslides has promoted the evolution of landforms to a certain extent.The occurrence of large-scale landslides led to the diversion of the Yarlung Zangbo River.(5)The larger Medog fault activity weakened the integrity of the rock mass on the left bank of the Yarlung Zangbo River,and the rock mass in the fault zone was broken.The location of the Qiangqiang source area makes the ground motion response of the left bank slope stronger than that of the right bank.The intensity of the strong earthquake zone in the Chayu area is high and the intensity is high.The faulty fragmentation of the left-off Medog fault zone and the potential of the left bank for the strong source area have laid a geological foundation for the formation of large-scale landslides on the left bank.