The Research Of Tipper Response Characteristics In Controlled Source Electromagnetic(CSEM)

The research in this paper is based on CSAMT.Compared with traditional MT,CSAMT has the following remarkable advantages: using artificial source,improving efficiency,deep detection depth,being less affected by terrain factors,high resolution,etc.There are more than 20 parameters in the observation data of electromagnetic exploration which can provide reference basis for the interpretation of underground geological structure.At present,the two main parameters used for quantitative interpretation are apparent resistivity(amplitude)and impedance(phase),while the other parameters are only used for qualitative reference.Tipper is proposed with the concept of impedance,which mainly reflects the direct relationship between vertical magnetic field and horizontal magnetic field.It can sensitively reflect the characteristics of horizontal inhomogeneity of underground geological structure,and plays a very important role in the interpretation of underground structural media.Through theoretical foundation research and forward modeling,the distribution law of the tipper data in underground media is analyzed,and one-dimensional inversion research is also carried out,which lays the foundation for the use of the tipper data in the interpretation of underground geological structure.In this paper,starting from Maxwell equations and based on electromagnetic field theory,the equations of each component of the electromagnetic field in the frequency domain of the electric dipole in the horizontal layered medium are deduced,and the concept of the tipper in the magnetotelluric sounding method is used for reference to complete the derivation of the tipper theoretical formulas in the controlled source tipper electromagnetic method.Secondly,on the basis of the theoretical formula,the forward simulation of the CSEM is completed,in which the Hankel integral is used to solve the forward calculation.Through the analysis of one dimensional forward modeling results,understand tipper data distribution in the underground medium,i.e.,by comparing the relationship between the apparent resistivity and the tipper amplitude,phase and frequency,the relevant law is found,which indicates that the tipper data has a good physical property foundation for the exploration of controlled source electromagnetic method,and the one-dimensional forward modeling research also lays a foundation for the subsequent three-dimensional forward modeling and one-dimensional inversion research.Then,using the numerical method of integral equation,the rectangular meshes of the study area are divided,and the three-dimensional forward simulation is realized.The forward modeling results show that the tipper response is sensitive to the lateral inhomogeneous anomalies.Can be seen from the tipper amplitude response figure,tipper,like traditional use of the parameters of apparent resistivity,can show the abnormal underground geological information,and to the right in conformity with the forward model,with parallel to the direction of the source profile controlled source electromagnetic method tipper Tzx real part,imaginary part and amplitude response most can reflect the underground abnormal body boundary and form,and its vertical resolution is poor.It can be concluded from the tipper three-dimensional map that the tipper phase data can accurately display the central position information of the underground abnormal geologic body.Under the condition of different frequencies,the tipper responses are different,which indicates that the tipper has the function of sounding depth.Finally,the one-dimensional inversion of controlled source tipper is studied.The advantages and disadvantages of several inversion methods of electromagnetic exploration data processing are briefly introduced.The self-adaptive regularization inversion method is introduced in detail,including the regularization factor,roughness matrix and the calculation of data variance matrix.To one dimensional inversion program of data processing and inversion trial according to different theory model,concluded that the inversion method is of high efficiency,the inversion results with the real model is close to,can intuitively given the change tendency of the underground resistivity with depth,the reliability of the adaptive regularization inversion algorithm,and lay a solid foundation for the further theoretical research.In summary,through the basic research on the application of controlled source tipper electromagnetic method,this paper realizes that tipper data can be used for the interpretation of underground geological structures,and the tipper phase can play a very important role in delineating the central coordinates of abnormal bodies.