TECTONIC DEFORMATION AND STRONG EARTHQUAKE ACTIVITIES ON THE EAST BORDER OF TIBET PLATEAU

The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly discusses the characteristics of tectonic deformation and strong earthquake activities on the east border of Tibet Plateau.1\ Characteristics of tectonic deformation on the east border of Tibet Plateau\;Controlled by the flow of the plateau crust material, the movement of the east border of Tibet plateau is mainly horizontal so as to produce two slipping\|block: one results from the slide out of Chuandian Rhombus Block along the SSE direction, the other results from the lateral extrusion of Chuanqing Block with the SEE direction. The slip rate of the north part of Chuandian Rhombus Block, the west region of Sichuan, is 5～8mm/a;2～3mm/a on the south part (the center part of Yunan); the slip rate of Chuanqing is 3～5mm/a and <1mm/a on Longmenshan region (Tang Rongchang, 1993). The slipping features of the blocks directly decide the movement characters of different fault systems: the uniform sinistral shear movement on the east boundary fault of Chuandian Rhombus Block, from the geological viewpoint, the average horizontal slip rate is about 10mm/a, and 5～8mm/a on the Anninghe, Zemuhe and Xiaojiang faults. The dextral shear movement can be found on the west boundary faults composed by Jinshajiang and Honghe faults. Located at the dextral diagonal region between Honghe and Zhongdian faults, the northwestern region of Yunnan shows a tensile stress field with near EW direction and large graben valleys with near NS direction on the ground due to the dextral slip movements of these two faults and slip of Chuandian Rhombus Block along the SSE direction. The normal features of extension tectonic deformation region can be found in this region. Some inner faults (such as Amaniqing, Xiqinglingbeilu) of Chuanqing block show the character of sinistral shear movement with some components of normal slip movement. As the east boundary of Tibet plateau, Minshan and Longmenshan Mountains form the east wall of the plateau. Contrasting to the moving direction of Chuanqing block, the transition from horizontal movement to vertical movement produced the huge nappe reverse deformation in this region, and formed some front\|Mount compensating press\|sag basins such as Gonggaling, Zhangla and Chengdu. Because of the diversity of slip rate of different boundary faults, some clockwise rotating movement can be found in different sub\|blocks.

The tectonic deformation image of Asia Continent can be explained successfully by the model of collision between India secondary continent and Euro\|Asia Plate (P. Molnar and P.Tapponnier, 1975). This paper mainly discusses the characteristics of tectonic deformation and strong earthquake activities on the east border of Tibet Plateau.1\ Characteristics of tectonic deformation on the east border of Tibet Plateau\;Controlled by the flow of the plateau crust material, the movement of the east border of Tibet plateau is mainly horizontal so as to produce two slipping\|block: one results from the slide out of Chuandian Rhombus Block along the SSE direction, the other results from the lateral extrusion of Chuanqing Block with the SEE direction. The slip rate of the north part of Chuandian Rhombus Block, the west region of Sichuan, is 5～8mm/a;2～3mm/a on the south part (the center part of Yunan); the slip rate of Chuanqing is 3～5mm/a and &lt;1mm/a on Longmenshan region (Tang Rongchang, 1993). The slipping features of the blocks directly decide the movement characters of different fault systems: the uniform sinistral shear movement on the east boundary fault of Chuandian Rhombus Block, from the geological viewpoint, the average horizontal slip rate is about 10mm/a, and 5～8mm/a on the Anninghe, Zemuhe and Xiaojiang faults. The dextral shear movement can be found on the west boundary faults composed by Jinshajiang and Honghe faults. Located at the dextral diagonal region between Honghe and Zhongdian faults, the northwestern region of Yunnan shows a tensile stress field with near EW direction and large graben valleys with near NS direction on the ground due to the dextral slip movements of these two faults and slip of Chuandian Rhombus Block along the SSE direction. The normal features of extension tectonic deformation region can be found in this region. Some inner faults (such as Amaniqing, Xiqinglingbeilu) of Chuanqing block show the character of sinistral shear movement with some components of normal slip movement. As the east boundary of Tibet plateau, Minshan and Longmenshan Mountains form the east wall of the plateau. Contrasting to the moving direction of Chuanqing block, the transition from horizontal movement to vertical movement produced the huge nappe reverse deformation in this region, and formed some front\|Mount compensating press\|sag basins such as Gonggaling, Zhangla and Chengdu. Because of the diversity of slip rate of different boundary faults, some clockwise rotating movement can be found in different sub\|blocks.