Recent developments in the magnetotelluric prospecting method

The magnetotelluric (MT) method has been greatly improved during the last ten years (Vozoff, 1972; Clarke et al., 1983), so it is now possible to get reliable and accurate results in any kind of survey, even in the presence of cultural noise. A few contractors now offer MT services for low-cost basin reconnaissance, structural surveys, and for geothermal and mineral prospecting. In spite of the range of different design options, some common characteristics can be sifted out from an analysis of available commercial MT systems. The most important of these common characteristics are reviewed in this article, and it is suggested that these should be regarded as 'standard' for any up-to-date MT system. The main differences between the various available acquisition and processing systems are described next, with a brief discussion of the advantages of each technical option. Finally, an automatic technique of timeseries 'pruning' the MT signal is described, which constitutes a pre-processing stage in the time domain.