Magnetotelluric Impedance Geological Noise Distortion And Correction Methods

Curve distortion is common in MT survey. If the distortion of the impedance data is not eliminated, the resistivity and phase of the TE and TM mode calculated by the common rotating principal axis may be wrong, which effluence on the result of data processing and interpretation.The paper deduces the impedance distortion formula resulting from geological noise from general situation. By forwardly calculating the theoretical models under the effluence of the distortion factors, the author draws some regular conclusions, which are conductive to study the impedance effluence from the distortion factors.In this paper, a method to calculate regional impedance from the data in which the distortions have been eliminated is presented. It proves to be effective by inverse calculation of the theoretic data and the observed data in the field. The method avoids the following problems of GB decomposition. Firstly, there are too many parameters to be calculated. Secondly, it is necessary to constraint the parameters to be calculated, thirdly, the observed errors have much effluence on the inverse results, fourthly, it is difficult to calculate in some cases, and the last is that the 3-D information is lost.The necessary resistivity and phase curves are selected according to the features of resistivity and phase in the field and the GA is used to calculate the distortion factors, which proves to be practical and effective.