“…A. Stodt, unpublished report, 1980]. Subsequently, the robust M estimates (RME) [ Huber , 1981; Rousseeuw and Leroy , 1987] have been applied to estimate the impedance functions [ Egbert and Booker , 1986; Chave et al , 1987; Chave and Thompson , 1989; Jones et al , 1989; Larsen , 1989; Sutarno and Vozoff , 1989, 1991; Larsen et al , 1996; Egbert and Livelybrooks , 1996; Egbert , 1997; Shalivahan and Bhattacharya , 2002; Smirnov , 2003]. Banks [1998] has studied the effect of nonstationary noise on electromagnetic response estimates in the frequency range of 0.05–0.000167 Hz.…”