Essais d'amelioration du traitement et de l'interpretation des enregistrements magnetotelluriques
J. P. Rocroi and P. Andrieux
Journal name: Geophysical Prospecting
Issue: Vol 23, No 4, December 1975 pp. 749 - 764
Info: Article, PDF ( 750.33Kb )
The MT method has proved to be a useful tool for the resolution of some geophysical problems not well adapted to seismic prospecting. To meet the accuracy needed by such cases, the original field and processing techniques has to be somewhat improved.
The processing of the natural EM field (with two electrical and three magnetic components recorded) is made in the frequency domain, and the usual MT parameters are calculated. However, the dispersion of the results is given a great importance and the final plots (apparent resistivity vs. frequency, azimuths of the main directions vs. frequency, etc.) illustrate the distribution of the calculated values.
Average curves can then be selected and studied by means of the known master curves. However, if the earth can be assumed to consist of parallel layers, a computer program derives from the apparent resistivity diagram an automatic solution consisting of a great number of layers with the same ratio of thickness to square root of resistivity. This comprehensive solution is then simplified through an auxiliary diagram called the MT Dar Zarrouk curve and a set of geologically consistent solutions can be found.