Magnetotellurics: An Overview

Magnetotellurics (MT) is an electromagnetic, passive geophysical method that permits to explore the electrical resistivity distribution inside the Earth. It takes advantage of the naturally variable geomagnetic field at Earth's surface that induces secondary electromagnetic field in the diffusive limit. Both the investigation depth that may range from tens of meters to several tens of kilometers or more and the sensitivity of electrical resistivity to fluid presence contribute to the increasing interest in this geophysical method, whose recent progresses have been valuable. Basic theory of the magnetotelluric method along with the properties of the transfer function, or impedance tensor, and its estimation are presented. Finally, a brief overview of the MT application with particular attention to the monitoring experiments is given, in order to guide the reader to search for specific research literature.