Study On The Of Landslides By Active Tectonics In The North West Of The Eastern Himalayan Syntaxis Region Of Tibetan Plateau

The eastern Himalayan syntaxis is located at the most leading part of the collision between the India plate and Eurasian plate.It is a complex area with strong crustal movement,strong tectonic activity and frequent earthquake.The complicated geological environment gives birth to the geological disasters which are mainly collapses,landslides and debris flows.Frequent geological disasters pose a great threat to the life and property safety of the people in the area.On the basis of extensive collection of previous geological data,this paper has carried out remote sensing image(satellite imagery,drone aerial imagery)analysis,field investigations of active faults and landslides on the northwest side of the eastern Himalayan syntaxis,and studied the Quaternary movement characteristics of the active faults(offensive micro-landform evidence and activity time)in the study area.The development rule of landslide in this area,the controlling effect of active fault on the spatial distribution of landslide,and the formation mechanism of landslide are systematically analyzed.The following understanding is obtained:(1)The Jiali fault is one of the main active faults in the study area.The fault is a right-lateral strike-slip fault in the northwest direction.It shows a strong activity in the Quaternary period,and the activity of the fault is distinctly different in different structural locations: The activity of the northwestern section of the Jiali Fault is the strongest,whereas the activity of the southwestern section is relatively weak,and the activity of the middle section is the weakest.(2)The Linzhi-Dongjiu fault is also one of the major active faults in the study area.This fault is a north-south-oriented,left-lateral strike-slip and thrust fault,withstrong Quaternary activity.The different parts of the fault have different nature.The Milin-Dongjiu section is dominated by left-lateral strike-slip,whereas the Layue-Pailong section is dominated by thrust.(3)The types of landslides in the study area include rocky landslides and soil landslides,and the main landslides are soil landslides.Among them,25 are rocky landslides,accounting for 29.8%of the total number of landslides,and 59 soil landslides,accounting for 71.2% of the total landslides.In space,rocky landslides are mainly distributed in the middle of the study area from Layue Village to Tongmai.Soil landslides are mainly distributed in the north of the study area from Suotong to Tongmai and in the south of the study area from Dongjiu to Lulang.(4)The distribution of landslides in the study area is related to the intensity of fault activity,fracture properties,and the intersection of faults.The number of landslides on the Linzhi-Dongjiu fault zone is more than that on the Jiali fault zone,mainly due to the Linzhi-Dongjiu fault as a left lateral strike slip and thrust fault.The number of landslides on the Layue-Pailong thrust fault is much larger than that of the Milin-Dongjiu left-lateral strike-slip fault,indicating that thrust faults are more likely to trigger landslide geology disasters.The distribution of landslides on the Layue-Pailong fault zone has a “hanging wall effect”,and the number of landslides on the hanging wall is significantly higher than that on the footwall.The number of landslides developed at the junction of the junctions of the Jiali and Linzhi-Dongjiu faults near Tongmai was significantly higher than that of other parts of the Jiali fault,indicating that landslide geology disasters are more likely to occur at the intersections of the faults.(5)Through the analysis of the basic characteristics,formation mechanism and sliding process of typical earthquake landslides,the landslide in the study area is considered to be the product of historical earthquakes,active faults,and climatic conditions.The active tectonics is the main controlling factor.The formation mechanisms of the two types of landslides also have a certain difference.The rocky landslides are mainly controlled by the tectonics,because of the joint extrusion and uplift of the active faults to the nearby mountains,the joint fracture development of the rock mass,the destruction of the rock mass structure,the cumulative superposition of historical earthquakes,and the formation of the rock landslides eventually.However,the onset time of soil landslide in the study area is basically concentrated in the rainy season,and rainfall plays a controlling role in the formation of soil landslide.