Data Processing And Interpretation Of Long Magnetotellurics Profile

This dissertation is supported by Sinoprobe-02-04,observation experiments of magnetotelluric(MT)soundings and research of crustal-mantle electrical structure.Aimed at long MT profile from Quanzhou to Hezuo,the dissertation applies advanced MT processing technology and inversion software to get complete electrical structure model.With this model,the author will research regional tectonics along the section and geophysical characteristics in the deep.Because of long section and huge data,the whole profile cannot be inverted in one time.In order to get the whole electrical structure model,the author attempted two different methods which are Resistivity interpolation and Station evacuated.The result is that Resistivity interpolation depicts detail more accurate,though it may produce small false anomalies during the interpolation process.And it's very important for MT whether in research or in production.The electrical structure model obtained by 2D inversion shows that:the resistivity is very high in the east while low in the west,the transition zone is East-Sichuan detachment fold belt which is between the Huayingshan Fracture and Huayuan deep fault in west of Hunan.On the west of the belt,the lower crust of Songpan-Ganzi terrane shows high conductivity which reflects that the deep materials of Tibetan plateau is very weak.While the low resistivity of lower crust in Sichuan Basin is an electrical performance of thick deposited layer with a resistive basement below.On the east of the belt,Yangzi block and Cathaysia block shows high resistivity and mixed with high conductivity in some areas which reveals these tectonics experienced lift and erosion in Neotectonic movement.The model reveals high resistivity in shallow and high conductivity in deep in Songpan-Ganzi area which is opposite of the Sichuan Basin.Near Longmenshan Fault zone,the model shows high-low-high resistance characters,reflecting the fracture plays a thrust nappe role.On the east of the Huayingshan Fracture,GPS velocity data shows the speed direction of East-Sichuan detachment fold is pointing to SE.Combined with electrical structure of high conductivity in shallow and high resistivity in deep,this information reflects the reason for the formation of the belt:under stress,the low resistance sedimentary slide along the surface of the continuous stable rigid high-impedance substrate.Formed in Yanshan movement,Huanan block lift and erosion during Neotectonic movement,shows high resistivity as a whole and mixed with high conductivity in some areas at last.