“…Regional electrical conductivity anomalies are distributed all over the world and characterize different plate tectonic provinces (Hjelth and Korja, 1993). Several continental rifts (Jiracek et al, 1995), high heat flow areas (e.g., Ingham et al, 1983;Sakkas et al, 2002), enhanced seismic reflectivity layers (e.g., Hyndman, 1988), sedimentary basins (Arora et al, 1999), regional fault systems and terranes boundaries (e.g., Jording et al, 2000;Armadillo et al, 2001Armadillo et al, , 2004Ledo et al, 2002) exhibit an electrical conductivity signature. At the Earth's surface magnetometers measure the composite of external (from the source currents) and internal (from the induced currents) field components.…”