Use of the Magnetotelluric Method in Brazil and Future Challenges

The magnetotelluric (MT) method is based on measurements of natural electric and magnetic fields at the Earth’s surface to probe the subsurface electrical resistivity structure. A summary of the use of the method in Brazil is presented, with emphasis on the initial theoretical and experimental developments for its implementation in the country. The expansion of the method in recent years is related both to academic studies on the tectonic evolution of geological provinces and to contracted surveys mainly restricted to support oil exploration. Two major challenges are proposed to increase the contribution of the method in the next years. One is the planning and installation of a large experimental program to obtain long-period data from stations installed in a 3D grid. It can contribute to improve the knowledge of the tectonic evolution of the Brazilian shield and also to locate new areas with potential for exploration of mineral resources. Coupled with this expansion of field measurements, another challenge is the need to formulate new data processing techniques. The main objective will be to minimize the effects of coherent and intermittent EM noise related to the installation in the country of electric power transmission networks using high voltage direct currents (HVDC).