Magnetotelluric Sounding Migration Imaging

In this paper, based on the essential MT theory, we have mainly discussed the following three aspects of technology:1. Magnetotelluric field phase shift migration tomographyWe introduce how to apply the seismic phase shift migration into MT interpretation. Based on 1-D single interface and 1-D multi-interface model phase shift migration, we analyze several significant factors which affect the results of MT migration. Then the process of 2-D MT phase shift migration is expatiated. We also use the PSPI method in seismic migration to make it suitable in more complex geoelectric section. Finally, both advantages and disadvantages of this technology are concluded, so was the foundation stone which brings these disadvantages.2. Magnetotelluric field finite difference migration tomographyFound on the researches of Zhdanov etc. in MT finite difference migration tomography, we analyze and summarize both fruits and limitation of foregone peoples' achievements. So more precise finite difference extrapolation equation can be deduced, and it can be easily applied into the migration tomography. New equation reserved the derivative terms of wave number both at vertical and horizontal direction, so that more exquisite geoelectric diversification can still be accommodated, that is the very requirement of practical data interpolation.3. Improvement of MT migration tomography technologyBased on the immanent relationship between tomography purpose and suitable frequency segment selection, we raise an entire frequency segment multi-parameter tomography scheme of MT finite difference migration. We establish a mathematical relationship among apparent electromagnetism reflectance, migration reflectance, background resistivity and the true resistivity distribution. After the introduction of TE/TM mode superpose rate, we carry out the associated resistivity tomography of two polarization mode to adapt the practical data interpolating situation.Ultimately, we compare the characteristics of phase shift migration and finite difference migration; contrast the differences between migration and common inversion; analyze several significant factors which affect the results; also enumerate several key-points in future research which could improve the migration mostly.