In the 50’s, French and Russian Physicists proposed to measure on the ground and passively the earth’s natural electrical (E) and magnetic (H) fields to derive the subsurface electrical resistivity.

The natural source of that method is created by the interaction of solar winds with the Earth’s magnetic field, by lightnings, spherics and ionospheric resonances (Schumann resonances).

Simplicity of the method, great depth of penetration and possibility to construct 3D resistivity images made MT a widely-used technology from tectonics to minerals and Oil & Gas exploration.

The current section is composed of 3 lessons:

Field equipment, feasibility survey, processing, interpretation and comparison with other geophysical methods (gravity and magnetism) are discussed in the field case devoted to geothermal exploration.

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