Study on Density Structure and Tectonic Movement of Xiaojiang Fault System

Abstract:

Xiaojiang fault system is an important part of tectonic movement in the eastern margin of the Qinghai-Tibet Plateau, formed a complex deep tectonic structure with strong tectonic movement in the east boundary of Sichuan-Yunnan block. We set up five cross-fault short gravity profiles with GPS position, and after 3 types of correction, topographical correction, gravity-height correction and Bouguer plate correction, we get the values of gravity anomalies caused by density heterogeneity of various geological features. We analysised its crust mass distribution of Xiaojiang fault system in northern, middle and southern section by the way of bouguer residual density correlation imaging, normalized full gradient and gravity inversion using selection methods. We got the crustal mass distribution image to the Moho, layered structures and fault structures, and then we analyzed its tectonic movement. The studies show that Xiaojiang fault system has the segmental features. There was more complex crustal structure in northern, and southern crustal structure is relatively simple but moho depth was more shallower. And we also found inhomogeneous density distribution in the transverse direction and layered distribution features in the vertical direction. The model of the fault system cross-fault gravity profile and three-dimensional space tectonic, based on rich geological and geophysical data in the area, provided the physical basis for the research of earthquake evolution in the area and material flow, dynamic environment in the eastern margin of the Tibetan Plateau.