Electromagnetic (EM) methods are widely used in geophysics to study the electrical properties of the subsurface. These methods involve the use of electromagnetic waves that propagate through the subsurface and interact with the electrical conductivity of the rocks and soils.
One of the most common EM methods used in geophysics is the transient electromagnetic (TEM) method, which involves the use of a transmitter to send a pulse of electromagnetic energy into the subsurface. The energy induces electrical currents in the subsurface, which in turn generates a secondary electromagnetic field that is measured by a receiver. The measured signals are then analyzed to determine the electrical conductivity of the subsurface.
Another commonly used EM method is the frequency-domain electromagnetic (FDEM) method, which involves the use of a transmitter that emits a continuous wave at a specific frequency. The electrical currents induced in the subsurface by the electromagnetic energy depend on the frequency of the wave and the electrical conductivity of the subsurface. By varying the frequency of the wave and measuring the amplitude and phase of the secondary electromagnetic field, it is possible to obtain information about the electrical conductivity of the subsurface at different depths.
EM methods are used in a wide range of geophysical applications, including mineral exploration, groundwater studies, environmental studies, and engineering projects. These methods can provide detailed information about the subsurface structure and properties, which can be used to improve our understanding of geological processes and to guide resource exploration and development. However, interpretation of the data obtained from EM methods requires expertise in both geophysics and geology.