Tectonics Activity Of The Nujiang Fault Zone In Quaternary In The Southwest Yunnan

Active faults is one kind of displays of recent tectonic activity, and is closely related to the earthquake occurrence. the activities reflect features of crustal deformation and movement in the recent or the latest geological time. The fundamental quantitative parameters, provided by active tectonic researches, which include active history, movement feature, slip rate, fault segmentation and segment length and co-seismic displacement. will offer an important window for us to understand the geodynamics of lithosphere, the recent plate movement and intra-plate deformations. Nujiang fault of the western Yunnan is a large inner continental strike-slip fault in eastern Tibetan margin. It is closely related to uplift of the Tibetan plateau. Therefore, the studies of tectonics activity of Nujiang fault contribute to understand the formation and evolution of the Tibetan plateau, to reveal the movement form and mechanism of eastern extrusion or escape of Tibetan plateau, to reflect interaction process of Indian and Eurasian plate.Based on background of development of rift basins, clue of finding out active fault, study subject of fault controlled basin, and Combined with the phenomenon of Geomorphology, the thesis investigates tectonic activity of Nujiang Fault during Quaternary. The role in the eastern extrusion of Tibetan plateau and Eastsouthern escape of Indian plate. The main contents of work are summarized as blew:1.Nujiang Fault within the borders is obviously divided into east branch and west branch of Nujiang fault of in the Nouth of Daojie. The ends of Nujiang fault, believed to Longling-Ruili fault, bended, caused trending transformation from South-North into Southwest, which resulted in development of extensional tectonics in the both sides of Gaoligongshan, extended to Myanmar, because of circumgyrate resulted from ES-trending escape of Indian plate during 11~14Ma. Extensional tectonics had a development trend from south to north.2.Study region is located in the Southwest Yunnan Block right-laterally circumgyrating. Through study of regional geodynamics, it is obtained that modern tectonic stress field is characteristic of SN-direction compression and EW-direction extension, stress structure is main strike-slip. Orientation of stress field is basically in accordance with the former study results.3.Through research about activity of East branch of Nujiang fault, it was found that Daojie Basin and Zhen'an Basin, controlled East branch of Nujiang fault, had new activity since late Pleistocene. River terraces in the Daojie section of Nujiang drainage area show that mean uplift rate is 2.43mm/a since late Pleistocene. Study of East branch of Nujiang fault through other method indicates that the newest activity occurred during Early and Middle Pleistocene. The phenomenon reflects that right-lateral block circumgyrate had influence on the section of Nujiang fault, and resulted in activity of the fault.4.Northeast trending Longling-Ruili fault, turning Point of West branch of Nujiang fault, transformed from right-lateral into left-lateral strike-slip, which assort with plate right-lateral circumgyrate of plate.5.Researth indicates that newest activity of Longling-Ruili fault occurred at after late Pleistocene. The age is younger than South-North section of Nujiang fault。...