An overview of electrical resistivity in the crust and upper mantle: Principle of magnetotelluric method, accuracy and resolution of resistivity modeling, and electrical resistivity feature of crustal and mantle rocks and minerals

Electrical resistivity is known as a good indicator for geo-fluid distribution especially in the crust and upper mantle. In this paper, we introduced physical concept of electrical resistivity in solid, liquid, and their mixing law, which can explain resistivity of crust and upper mantle. We also introduced magnetotelluric method, a common exploration method to image resistivity distribution in the earth, and modeling (inversion) method for resistivity distribution. Because resolution of inverted resistivity model from the magnetotelluric data depend on depth, resistivity, density of observation station and smoothness constraint, the model should be carefully interpreted. The magnetotelluric method has been applied for various tectonic settings. Many studies discovered low resistivity zones probably indicating fluid-rich area in or beneath the earthquake faults. In the volcanic zones, partial melt and hydrothermal areas were inferred based on three-dimensional modeling. Intensive MT surveys and newly developed interpretation techniques such as correction method of bathymetry effect and 3-D inversion method enable us to image resistivity of subduction slab and oceanic plate.