Introduction
Images of the electrical conductivity can help decipher the architecture of the Earth's interior. The magnetotelluric (q.v.) method (MT) is one of the few tools capable of imaging from the Earth's surface through to the mantle. Regional studies of EM are conducted to image the conductivity distribution of the subsurface on the scale of a few kilometers to hundreds of kilometers, both in lateral and depth extensions.
The electrical resistivity (
) and its inverse the electrical conductivity (
) characterize charge transport within materials. They are intrinsic material properties, independent of sample size. Rocks and rock‐forming minerals vary in their electrical properties, with conductivities ranging from 
to 
.
The MT method is based on the induction of electromagnetic fields in the Earth (see Natural sources for EM induction studies ). The MT impedance tensor Z and the geomagnetic response functions (see Induction arrows and Geomagnetic Deep sounding ) are the Earth's...
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Ritter, O. (2007). Em, Regional Studies. In: Gubbins, D., Herrero-Bervera, E. (eds) Encyclopedia of Geomagnetism and Paleomagnetism. Springer, Dordrecht. https://doi.org/10.1007/978-1-4020-4423-6_93
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