Research Of Faults Features And Its Implications On Distribution And Formation Of Landslides In Bailongjiang Region,Gansu

The Bailong River region is located in intersection of Tibet Plateau,Loess Plateau and Sichuan Basin,On the plate tectonics it is located in junction area of Qin Qikun orogenic system,Tibet Sanjiang orogenic system and The Yangtze continental block,while is located in the North of North-South seismic belt,which have a lot of faults,active neotectonics,frequently earthquake,intense down-cutting,great height difference and concentrated heavy rainfall,the complicated geological condition and environmental factors made this area the one of high-occurence zones for geological disaster.The Bailong River area is specially characterized by extensive landslide disaster,high frequency of disaster and multiple contributing factors.Until now,although several researches about mechanism of landslide disaster,few specialized researches about the critical role of fault structure in the development of landslide.This low degree of research severely restricted the clearly understanding of disaster mechanism,further constraints the development of comprehensive assessment of landslide disaster and also impedes the working of major landslide disaster prevention.So the study for interrelation between Bailong river fault activity and the landslide distribution become important to understanding of landslide formation development and prevention.First,we collated and summarized the existing research materials,then used wild geological and environmental survey,faults occurrence and fracture zone and a part of landslides features have investigated and measured,after this,summarized the regional constructed background and constructed stress field of the study area and the faults features and landslide features,based on the spatial analysis of GIS,establishing the line shaped buffer analysis for faults in study area and combining the example-Dengqiao landslide and Huama-Zhongpai landslides group,researched the faults features and its implications on distribution and formation of landslides,reached the following main conclusions:(1)The main faults within Bailong River region along NW and NWW to extend,followed by the NE to distribution;the faults trends in NW direction to the north of Wudu but in NE direction to the south of Wudu;The faults activities took place in the period of Caledonian,Hercynian,Indosinian,Yanshanism and Himalayan.Among these periods,the Hercynian and Indosinian were the periods whose faults strongly developed.In the Yanshanism and Himalayan the faults inherited the former tectonic directions.Basically,the tectonic stress field is compression in the NE-SW direction and extension in the NW-SE direction..(2)Landslides in the study area give priority to with large and medium-sized which have poor stability;The type of landslide are:bedrock landslides,colluvial landslide,loess landslide and loess-red layer landslide,the number of colluvial landslide is more and most developed.95%of landslides within Bailong River region main along the extend direction of big fault and secondary fault distribute,which is divided into three concentrated area:first one is Bailong River fault zone concentrated distribution with(66.9%),main distributed in Wudu district(43%),and Zhouqu County,especially in Zhouqu-Wudu area,and Beiyu river basin;second one is Baishui river basin concentrated distribution with(Shifang-Linjiang fault zone)(22%):main distributed in Shijiba-Bikou of Wenxian County which along the valleys and the near mountains;third one is Zhuyuan fault zone distribution with(6%),distributed in Tanchang County,mainly in the Huama area.(3)The buffer of faults showed that it has a high correlation between landslides and faults,as evidenced in faults controlling the scale,extending direction and distributional density of landslides,clustered and striped characteristic of landslides largely coincide with the extended directions,locations of faults.Spatial distribution and scale of landslides in Bailong River basin were controlled by faults,landslide points in the distance within 2.5 km of faults accounted for 70.6%of the total number of landslides in the region.(4)Dengqiao landslide and Huama-Zhongpai landslides clusters occurred have a close relationship with faults activities in Bailong River upstream,the border of landslides were controlled and traversed by faults,the landslides(landslide clusters)are located in the hanging-wall of the thrust fault,joints in parallel and perpendicular to fault strike are development in rocks which are favorable for rocks crack and formation of weak structure planes,and the normal faults activations within the hanging-wall of the thrust faults intensified the probabilities of the landslide formation.