Transient electromagnetic response of a loop source over a rough geological medium
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The theory of the transient controlled-source electromagnetic (EM) response of a loop source over a rough geological medium is developed in this paper. The governing fractional diffusion equation in the Laplace domain is solved semi-analytically, and the Gaver-Stehfest algorithm is then used to to numerically invert the associated Laplace transform. The geological medium is characterized by a spatially uniform roughness parameter β, which provides a more realistic description of subsurface geoelectrical structure than does a traditional piecewise smooth representation. Practitioners of the transient EM method can detect the presence of rough geology via observing a departure from the classical γ = -5.2 value of the late-time response slope along with a power-law behaviour of the zero-crossing time τH (L) as a function of transmitter-receiver separation. Field studies have indicated that rough geology can explain certain controlled-source EM responses with an economy of model parameters. © 2009 The Authors Journal compilation © 2009 RAS.
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