Remote Sensing Interpretation Of Active Faults In North-central Tibet

Active faults refer to faults that have been active since the late Quaternary(100000～120000 years)which are the culprits of large earthquakes.They can be divided into Holocene faults and Late Pleistocene faults.The Holocene fault is the active fault that has displaced on or near the surface in the past 10000 years.The Active faults may cause seismic surface dislocation in the future,which will damage the project crossing the active fault.It is necessary to take measures to avoid or resist the fault.Therefore,finding out the distributions of active faults are the prerequisite for reducing earthquake disaster losses and disaster risks.The Qinghai-Tibet Plateau is a typical strong earthquake-prone area with wide distribution of seismic activity,high frequency,high intensity and shallow source.In this paper,the active faults in the central part of northern Tibet are taken as the research target to interpret the active faults by remote sensing.The active faults within the scope of the study are investigated in detail,including large-scale active faults with strong seismic capacity,as well as small-scale faults with high activity.In this paper,satellite remote sensing images are used to determine the locations of the faults,identify their characteristics,and assess the ages of their latest activity and quantitative parameters such as intensity.Satellite remote sensing interpretation is the most important method to study active faults.This is especially true in the Tibetan Plateau region,where active fault traces are clear and lack overlying Quaternary layers.High-resolution satellite remote sensing images can capture various tectonic and geomorphological phenomena formed by fault activity.Seventeen Holocene active faults in the study area were interpreted using high-resolution satellite images.It includes Margai Chaka fault,Yibuchaka graben,Riganpeicuo fault,Qingwahu fault,Dongcha fault,Qixiangcuo fault,Kangxiwa fault,Altun fault,Guozhacuo fault,Longmucuo fault,Zecuo fault,Mushirebuka fault,Xiaxiazangbu fault,Nawucuo fault,Nieercuo fault,Buergacuo fault,Karakoram fault.When analyzing each fault,typical images with evidence of active faults are intercepted,and the typical remote sensing image features of active faults are summarized.It is clear that the typical remote sensing image of active fault is the remote sensing image that can reflect the dislocation of late Quaternary strata,geological body and geomorphic surface(unit).Combined with previous research results and regional comparative analysis,the latest activity age,activity nature and activity intensity of the Holocene faults in the area are discussed,as well as the overall tectonic movement characteristics and seismic ability of the active structures in the area.The western branch of Longmu Co fault,Guozha Co fault and the western end of Altun fault in the northwest of the study area constitute an en echelon distribution of NEE-trending left-lateral strike-slip fault system.The dextral strike-slip fault of the NW-trending Karakoram fault forms a large conjugate strike-slip system in the western border area of Tibet.The NE-trending left-lateral strike-slip fault on the Qiangtang block and the right-lateral strike-slip fault on the Lhasa block also constitute a ’ V ’-shaped conjugate strike-slip fault system.The fault system is considered to be conducive to the eastward extrusion of the Qiangtang terrane relative to the Lhasa terrane.The difference in the eastward movement speed at different locations within the Qiangtang formed a series of dispersed conjugate strike-slip fault systems and SN-trending normal faults.The above faults reflect that the area is squeezed in the north-south direction to form a V-shaped conjugate system,and the overall movement characteristics are the dynamic environment of the block extrusion eastward.