An implication of the Hilbert Transform to the magnetotelluric method

Noise is inevitably encountered when the tensor magnetotelluric (MT) method is used for geophysical sounding purposes. It is shown that, for many cases, the magnitudes of the impedance elements are biased by noise on the MT data channels, whereas the phases of these elements are unbiased. A practical method for deriving or smoothing the amplitude data by phase information is presented in this dissertation. The means for accomplishing this is based on the Hilbert Transform operation on minimum phase MT impedance functions. The formulas for the use of this method are developed, and some practical considerations are given for the implementation of the phase smoothing process. A theoretical model with and without synthetic noise is analyzed through this process to illustrate the validity of the technique. Also shown are several examples of results from this process as applied to actual tensor magnetotelluric impedance data.