A Magnetotelluric Survey in Southern Portugal

In the summer of 1990 a magnetotelluric (MT) survey was performed in southern Portugal to try to delineate the geoelectrical structure of a geothermal anomaly reported to exist there. Although the geological and electrical characteristics of the region of the MT study are apparently three-dimensional, a twodimensional modelling approach is being used for an initial interpretation of the data. The objective of this approximation is twofold. First, it allows a preliminary geoelectrical interpretation for the region; second, it will provide bounds for the construction of a threedimensional model for detailed interpretation and which will be closer to the actual geological character exhibited in geologic and tectonic maps of the area. The main features seen in the results of the numerical models are also seen in the results of the measured data. Low electrical resistivity zones which coincide with fault structures that cross the region are evident in both the model and data pseudosections.