Geophysical Journal | 2004 volume 26 5

On the problem of applying electromagnetic soundings for the studies of deep-seated structure of horizontally irregular media (according to simulation results)

© Kuznetsov A.N.

According to physical and three-dimensional mathematical simulation of soundings with artificial source under control and magnetotelluric sounding (IOS) suggestions have been made as to the choice of optimal method of frequency sounding (FS), field formation sounding (FFS), FFS-FSS (fastened source sounding), FS-FSS and IOS over geoelectric models of complicated horizontally irregular structure. Special features of manifestation of geoelectric section have been considered in case of application of different components of electromagnetic field, excited by different types of sources in temporal and frequency ranges in different zones of the source. Efficiency of application resistivity prospecting appliances of different geometry has been estimated in cases of variable orientation as to the main tectonic elements of the studied model of geoelectric section. Studies of the models with intermediate isolating beds within geoelectric section allowed to conclude that MTS method lacks efficiency for detailed studies of the strata, overlapped by high resistivity screens. Because of this, the complex with active electromagnetic methods is required in case of detailed MTS works. The effect of near-surface three-dimensional irregularities on MTS is essentially greater than was expected earlier, and it does not always fit in the notion of S-effect. Thus it is reasonable to perform preliminary choice of the site for sounding with the help of audio-MTS or resistivity profiling.

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