Pierre-andre Schnegg

A telluric survey and several magnetotelluric (MT) soundings have been carried out across the Ferrara High (northern Italy), in a geothermal area previously explored in detail during a search for oil. The aim was to compare telluric, MT and gravimetric data with a structural model derived from a seismic investigation in a region of fairly well-known geology. The comparison between observed and predicted telluric pseudo-sections reveals a much better agreement than expected, especially since the gravimetric field data clearly show that the structure is effectively 3-D whereas the comparison was restricted to a single profile with 2-D interpretations. The 3-D character seems to appear most clearly in the telluric parameters at periods > 10 s. In the search for a 2-D interpretation of the telluric and MT data, an attempt was made to reduce the family of possible models by imposing external constraints. It was gratifying to find that the best fit with the seismic 2-D model was obtained when a uniform resistivity was required for each of the separate formations revealed by the seismic sounding.