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MAGNETOTELLURIGS: PRINCIPLE AND OUTLINE OF THE RECORDING TECHNIQUE A CASE HISTORY *
- Source: Geophysical Prospecting, Volume 22, Issue 1, Apr 1974, p. 107 - 121
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- 27 Apr 2006
Abstract
First, we review briefly the principle of the method, the computation of theoretical curves for a layered earth, and the recording technique in use in our surveys.
The case history deals with an area covered with overthrust nappes (marls of Miocene age), which had slid on a Triassic sole, obscuring the geological picture.
The magnetotelluric survey followed those of gravity and aeromagnetics and preceded the seismic one from North to South, it displayed a shallow and gently dipping basin, a major fault system, and a deep basin with a thick resistive layer, often underlying a conducting one.
The seismics, and later the drilling of a well East of the profile, confirmed these features; in particular, the thick resistive layer was revealed to be Jurassic; only its thickness had been slightly overestimated. This fact lead the people in charge of the operations to ask for a reinterpretation synthesis of magnetotellurics, seismics and gravity, the results of which are also presented.