Methods » Electromagnetic (EM)

Measurement of time-varying electromagnetic field generated by induction involve a lot of techniques related to measured component and EM field spectra.

The depth range is limited by the electrical conductivity of the ground and the transmitting frequency.

            It is also used for locating conductive base metals and buried ferro-magnetic sources.

• CSAMT: Controlled source audio-frequency magnetotellurics. Depth of exploration is controlled by frequency and earth resistivity. It is used to provide data on shallow and medium depth targets.
• THE MAGNETOTELLURIC (MT) method relies on induction of electric currents by natural magnetic field variations. At low frequencies, free-charge contributions to the anomalous fields produced by a conductive 3-D structure in a stratified medium dominate over the inductive contributions resulting in a galvanic distortion of the normal electric field, an effect known as current channeling. It is used to reveal deep buried structures in mining, thermal waters , oil and gas surveys or regional studies.
• GROUND-PENETRATING RADAR (GPR) uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiation in the microwave band (UHF/VHF frequencies) and detects the reflected signals from subsurface structures.
  It is used in a variety of media, including rock, soil, ice, fresh water, pavements and structures. It can detect objects, changes in material, voids and cracks.