| Since the Wenchuan Earthquake(Ms8.0)in 2008,whether it is out of tentative research on the prevention of earthquake disasters or the purpose of exploring geological resources,scientific research at home and abroad has given unprecedented attention to the scientific research of the Longmenshan tectonic belt.The Longmenshan fault zone in this area has always been considered as the boundary between the Songpan-Ganzi fold belt and the Sichuan Basin.It is the eastern boundary of the Qinghai-Tibet Plateau and the western edge of the Sichuan Basin.The Wenchuan earthquake occurred within the Longmenshan fault zone.Ying Xiuyi on the Beichuan fault.To solve the contact relationship between the Songpan-Ganzi block and the Yangtze basement in the Sichuan Basin,and the large-scale continental dynamics of Longmenshan,we learned that the three-dimensional lithospheric tectonic model is a necessary condition for research.In order to study the dynamics and movement of the continent,we must first determine the three-dimensional structural model of the lithosphere,and the research on the three-dimensional electrical structure of the lithosphere crust is an important part of the study.This research plan relies on the "Three-dimensional lithosphere electrical structure survey project in eastern Tibet and western Sichuan" and the Sino Probe project in the Longmenshan tectonic belt at 29°N-33°N latitude and 100°E-105°E longitude.Broadband magnetotelluric sounding point,comprehensive analysis of its data system,fine data processing,impedance and tensor GB decomposition technology,phase tensor analysis of the MRTZ impedance tensor data in the study area for dimensionality and electrical The analysis of the main axis shows that the main electrical structure in the middle-upper crust of the study area is a good twodimensional feature or even a one-dimensional feature,and the three-dimensional nature is relatively deep.Comparing different two-dimensional resistivity models obtained by two-dimensional inversion under different modes and parameter settings,the Mod EM three-dimensional inversion technique based on the NLGC inversion algorithm was also used to obtain the three-dimensional electrical properties of the Longmenshan structural belt for the first time.The model is verified by the reliability of the model,which provides three-dimensional basic data for the study of the geological problems such as the lithosphere structure and dynamic mechanism in the Longmenshan area.Using the three-dimensional electrical model obtained in this study and combining the known geological data of the Longmenshan tectonic belt and other geophysical studies,the conductivity of the underground crust-scale materials in the study area indicates that the Longmenshan fault zone and the Upper Yangtze In the deep subduction of the lithosphere on the western margin of the block,the high-resistance body on the western edge of the rigid Upper Yangtze block is not a simple wedgeshaped structure formed by a wedge-shaped structure.The upper-layer high-resistivity thrusting of the upper plateau in the upper plateau over the Longmen upper fault zone has only significant electrical responses in the central Longmenshan area.From the perspective of the electrical structure,the entire Longmenshan fault zone is not simply a two-dimensional structure along the fault zone.The western boundary of the Yangtze plate is irregularly distributed,and its westernmost end may reach the Longrioba fault.The low-resistance zone under the Songpangangan block also does not support the view of pipeline flow.The purpose of this study will help us to better understand the structural response of the eastern margin of the Tibetan Plateau in the land-continent collision process between the Indian Plate and the Eurasian Plate,the mechanism of the earthquake disaster in the Longmenshan tectonic belt,and the entire study area,conductivity situation. |
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