Distortion decomposition of the magnetotelluric impedance tensors from a one-dimensional anisotropic Earth

The Earth is anisotropic at all scales, and models and interpretations of electrical anisotropy from observations are becoming more common. The magnetotelluric (MT) impedance tensor from an arbitrary 1-D anisotropic layered Earth admits an unusual form of six parameters (three complex impedances) with diagonal terms that are equal but of opposite sign. This particular form, somewhat unappreciated and neglected to date, can be exploited to deal with regional MT data that are distorted by galvanic effects of near-surface scatterers. Following prior distortion decomposition approaches, a method is proposed that statistically tests for its validity and solves for the determinable parts of the galvanic distortion and recovers the regional 1-D anisotropic responses. The method is demonstrated on synthetic data and real MT data from two different locations.