Abstract

The same mathematical formalism of the wave equation can be used to describe anelastic and electromagnetic wave propagation. In this work, we obtain the mathematical analogy for the reflection/refraction (transmission) problem of two layers, considering the presence of anisotropy and attenuation -- viscosity in the viscoelastic case and resistivity in the electromagnetic case. The analogy is illustrated for SH (shear-horizontally polarised) and TM (transverse-magnetic) waves. In particular, we illustrate examples related to the magnetotelluric method applied to geothermal systems and consider the effects of anisotropy. The solution is tested with the classical solution for stratified isotropic media.

Highlights

  • The role of mathematical analogies has been well illustrated and explained by Tonti [1]

  • Carcione and Robinson [4] establish the analogy for the reflection-transmission problem at a single interface, showing that contrasts in compressibility yield the reflection coefficient for light polarized perpendicular to the plane of incidence (Fresnel’s sine law – the electric vector perpendicular to the plane of incidence), and density contrasts yields the reflection coefficient for light polarized in the plane of incidence (Fresnel’s tangent law)

  • Theories describing wave propagation and field diffusion in different fields of physics consist in partial differential equations, which have identical or similar mathematical expressions

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Summary

Introduction

The role of mathematical analogies has been well illustrated and explained by Tonti [1]. Carcione and Cavallini [2] found analogies between anelastic and electromagnetic vector wave fields, while Carcione et al [3] relate the medium properties. Carcione and Cavallini [2] show that the 2-D Maxwell equations describing propagation of the transverse-magnetic mode in anisotropic media is mathematically equivalent to the SH wave equation in an anisotropic-viscoelastic solid where attenuation is described with the Maxwell mechanical model. Carcione et al [5] considered the reflection/transmission problem through an anisotropic and lossy layer. They obtained the analogy among P and SH elastic waves, TE and TM electromagnetic waves and wave mechanics in quantum theory.

Reflection and transmission coefficients
Surface impedance and apparent viscosity
SH-TM analogy
Surface impedance and apparent resistivity
Example
Conclusions
Classical magnetotelluric solution for an isotropic Earth
Full Text
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