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Record 1,  Textual support,  English

Record number: 1, Textual support number: 1 DEF

[A] technique in which natural electromagnetic fields in the audio-frequency range are used to study lateral changes in earth resistivity.  1, record 1, English, - audio%20frequency%20magnetic%20technique

Record number: 1, Textual support number: 1 CONT

Experience with the AFMAG method has demonstrated that an electromagnetic exploration system using the Earth's natural audiofrequency magnetic fields as an energy source, is capable of mapping subsurface electrical structure in the upper kilometer of the Earth's crust.  4, record 1, English, - audio%20frequency%20magnetic%20technique

Record number: 1, Textual support number: 1 OBS

Closely related to the telluric and particularly to the magnetotelluric methods is a technique based on the measurement of natural magnetic fields at audio and subaudio frequencies. Known as "AFMAG" (for audio-frequency magnetic fields), this technique was introduced early in 1958 by S.H. Ward. ... The basic principle of the method is to measure the tilt of the plane of polarization of the audio-frequency fields. The azimuth is first determined to the nearest 10° or so with a detecting unit. The tilt is then measured along this azimuth ... The dip angles are plotted in profile form; anomalies on the profile can be interpreted on the basis of experience gained over known conducting bodies.  5, record 1, English, - audio%20frequency%20magnetic%20technique

Record 1,  Textual support,  French

Record number: 1, Textual support number: 1 DEF

Méthode qui utilise les champs magnétiques naturels créés par les ondes (prospection électro-magnétique).  3, record 1, French, - m%C3%A9thode%20AFMAG

Record number: 1, Textual support number: 1 CONT

La méthode AFMAG (Audio Frequency Magnetic) est une autre parmi les méthodes électromagnétiques à cette particularité près que la source émettrice naturelle est la partie du champ magnétique terrestre qui correspond à la bande audio (1-8000 Hertz), qui a son origine dans les décharges électriques atmosphériques (éclairs). [...] Cette méthode a été conçue et mise au point par S.H. Ward, W.O. Cartier, H.A. Harvey, G.H. McLaughlin et W.A. Robinson en 1958, dans le but d'obtenir une plus grande pénétration (de l'ordre de 700 m) des ondes électromagnétiques qu'on obtient avec les méthodes EM conventionnelles.  4, record 1, French, - m%C3%A9thode%20AFMAG

Record number: 1, Textual support number: 2 CONT

[...] la méthode AFMAG est basée sur les champs magnétiques de fréquences audio engendrés par des éclairs produits lors des orages électriques.  5, record 1, French, - m%C3%A9thode%20AFMAG

Record 1,  Textual support,  Spanish