Affiliation:
1. College of Oceanic and Atmospheric Sciences, Oregon State University, Corvallis, Oregon 97331
2. Department de genie mineral, Ecole Polytechnique, Montreal, Canada
Abstract
The first step in the interpretation of magnetotelluric (MT) data involves estimating [Formula: see text] frequency‐domain impedances, Z(w), from the raw electric and magnetic field time series e(t), h(t) (approx. [Formula: see text] real numbers/site) [e.g., Swift, 1967, Sims et al., 1971]. Superficially, this initial data reduction step is almost trivial. Making the usual MT assumptions that the external sources are spatially uniform, and allowing for noise in the simplest way, e and h are related in the frequency domain via the linear statistical model e = Zh + ε, (1) where ε represents noise. The impedance Z can then be estimated quite simply by Fourier transforming the time series, and using linear least squares (LS] to minimize the misfit to equation (1) [Sims et al., 1971]. Unfortunately, this simple approach can fail catastrophically for noisy data, producing estimates that are heavily biased or wildly oscillatory [e.g., Gamble et al., 1979a; Jones et al., 1989; Figure 1]. As a consequence a number of refinements to the simple LS approach have been proposed in an effort to guarantee impedance estimates that are useful for subsequent stages in the interpretation process.
Publisher
Society of Exploration Geophysicists
Subject
Geochemistry and Petrology,Geophysics
Cited by
60 articles.
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