CHAPTER 9: CONTROLLED SOURCE AUDIO-FREQUENCY MAGNETOTELLURICS
Kenneth L. Zonge, Larry J. Hughes, 1991. "CONTROLLED SOURCE AUDIO-FREQUENCY MAGNETOTELLURICS", Electromagnetic Methods in Applied Geophysics: Volume 2, Application, Parts A and B, Misac N. Nabighian
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Controlled source audio-frequency magnetotellurics (CSAMT) is a frequency-domain electromagnetic sounding technique which uses a fixed grounded dipole or horizontal loop as an artificial signal source. CSAMT is similar to the natural-source magnetotellurics (MT) and audio-frequency magnetotellurics (AMT) techniques; the chief differences center around the use of the artificial CSAMT signal source at a finite distance. The source provides a stable, dependable signal, resulting in higher-precision and more economical measurements than are usually obtainable with natural-source measurements in the same spectral bands. However, the controlled source can also complicate interpretation by adding source effects, and by placing certain logistical restrictions on the survey. In most practical field situations these drawbacks are not serious, and the method has proven particularly effective in mapping the top 2 to 3 km of the earth’s crust.
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Electromagnetic Methods in Applied Geophysics, Volume I, Theory presented the mathematical and physical foundations common to all EM methods. The purpose of Volume I was to help facilitate the understanding of the theory involved and to provide a limited amount of interpretational aids. Volume II, Applications is devoted to a method-by-method treatment of the principal EM techniques in common use.