Finite Element Simulation And Analysis Of Influence Factors Of MT Tipper Response

Forward numerical simulation technologies of magnetotelluric sounding (MT) data are developing rapidly, and have made great progress in recent decades. In geological interpretation, magnetotelluric data can provide a lot of parameters useful. At present, apparent resistivity and impedance phase calculated from observed data are still the most important parameters for quantitative interpretation. Howerver, as the promotion of production applications and the development of theoretical studies in depth, more parameters are needed for quantitative interpreting of underground structure, such as MT tippers^WAL rotation invariants and so on. This paper mainly discusses the MT tipper data by finite element simulation and analyzes the related influence factors, which aim to providing more sufficient and reliable conditions for the structure interpretation through understanding of characteristics of the tipper.Firstly, derive the differential equations in TE polarization model under a level electrical inhomogeneous dielectric model according to Maxwell equations. Secondly, get the boundary value problem and then transformed it into equivalent variational problem through studying boundary conditions. The finite element method is spilt by rectangular grid as its convenience when programming, and nonuniform-meshing is a great way to approximate the infinite boundary and keep the same accuracy at the same time. By calculating several typical model, the pseudosection map of abnormality tipper response fully verified that the tipper responses can reflect lateral heterogeneity of geological structure sensitively. Then briefly tipper response factors are studied, an the results show that the amplitude of Tipper abnormalities is related with not only the overlying layer conductivity、thickness and the observed frequency, but also is influenced by the conductivity contrast of both sides of the horizontal inhomogeneous media on the interface and the surface uneven body.Since the research of tipper data started late in domestic, the study is not mature. Vertical magnetic signal is too weak to observe, tipper analysis is not used in practice merely still. Further research is needed.