Dissertation > Astronomy,Earth Sciences > Geology > Geology, mineral prospecting and exploration > Geophysical exploration > Electrical prospecting > Method > Electromagnetic Method

Fine Magnetotelluric Inversion and Its Application in the Research of Crust-mantle Electrical Structure

Author JinYongJi
Tutor JinSheng
School Chinese Geology University (Beijing)
Course Earth Exploration and Information Technology
Keywords Magnetotelluric sounding Fine inversion Electricity structure The northeastern margin of the Qinghai - Tibet Plateau The shell high conductivity layer
CLC P631.325
Type Master's thesis
Year 2010
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This thesis, China University of Geosciences (Beijing) the Dajing areas of cooperation to be completed in November 2008 magnetotelluric long profile data as the basis. In the interior systems use state-of-the-art data processing methods, magnetotelluric data processing, reliable MT response. The advanced 2D inversion algorithms, through a series of fine inversion, the study area has a higher degree of confidence the two-dimensional structural model of the electrical. Magnetotelluric impedance tensor decomposition results, the study area underground medium body structural trend NW - SE, similar to the two-dimensional structure. By forward modeling experiment, the measured data inversion calculation research found that seismic velocity model, regional geological structure data to build the the fine initial model inversion calculation, to be able to play good underground the abnormal body's bottom boundary constraints role in the credibility of fine portrayed the electrical structure of the underground media, and to improve the resolution of the solution to increase the inversion results, the inversion effect can be further improved, fine inversion purposes. The research results show that: the distribution along the section within the of multiple abnormal electrical tape distortion with electrical gradient zone and distortion with the location and area of ??deep faults coincide contrast with the regional structural data, these faults band is also research the area within the boundaries of tectonic units fault zone. Sections electrical structure of the crust along the north-south direction the overall performance of vertical stratification characteristics of the north-south block. Crustal conductivity structure is divided into three electrical layers underground 100km depth range, that, under a high impedance layer, the middle of the high-conductivity layer; surface low resistivity layer may Cenozoic or Mesozoic-Cenozoic sedimentary layer. There is an obvious high-conductivity layer in the crust of the study area, located in the lower crust along the profile of the high-conductivity layer thickness variation is relatively large, gradual thinning of the high-conductivity layer from south to north, and the high-conductivity layer interface burial depth and the bottom of the interface changes. High-conductivity layer in the crust in the south of Lanzhou roughly horizontal, high-conductivity layer Lanzhou north was south-dipping morphology. High-conductivity layer of the study area may be the result of the role of partial melting of body fluid. On the one hand, the the formation rock crushing serious due to intense tectonic activity of the study area, may be the destruction of the impermeable layer, resulting in the deep fluid migration or release. On the other hand, studies have shown that, when the temperature reaches 550 ° C, the rock can be a partial melt, the Qinling fold lines and the Qilian fold system has a relatively high heat flow value for the the rock ore dehydration phase transition lead to partial melting of creating condition.

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