Remote reference magnetotelluric impedance estimation of wideband data using hybrid algorithm

Precise and accurate determination of the magnetotelluric (MT) impedance is fundamental to valid interpretation. This paper deals with the results of hybrid processing schemes in conjunction with the remote reference (RR), for a typical site out of several sites collected over the wide band data (similar to 10(3) to 10(-3) Hz). The standard practice of MT impedance estimation is the use of robust processing in conjunction with the remote referencing. The estimation by robust technique helps in reducing the effect of outliers in the electric field but is often not sensitive to the exceptional predictor (magnetic field) data, which are called leverage points. The data processed with robust M estimation (RME) exacerbated the bias problem in the dead band. The application of hybrid (coherence weighted estimation (CWE)+RME, rho-variance weighting+RME) and extra hybrid (CWE+rho variance+RME) approach helps in reducing the influence of both the outliers in the electric field and the leverage points. These two approaches perform considerably better than either data weighting scheme by itself.