Magnetotellurics

Magnetotellurics (MT) is an electromagnetic geophysical method for inferring the earth's subsurface electrical conductivity from measurements of natural geomagnetic and geoelectric field variation at the Earth's surface. Investigation depth ranges from 300 m below ground by recording higher frequencies down to 10,000 m or deeper with long-period soundings. Proposed in Japan in the 1940s, and France and the USSR during the early 1950s, MT is now an international academic discipline and is used in exploration surveys around the world. Commercial uses include hydrocarbon (oil and gas) exploration, geothermal exploration, carbon sequestration, mining exploration, as well as hydrocarbon and groundwater monitoring. Research applications include experimentation to further develop the MT technique, long-period deep crustal exploration, deep mantle probing, and earthquake precursor prediction research. The magnetotelluric technique was introduced independently by Japanese scientists in the 1940s (Hirayama, Rikitake), Russian geophysicist Andrey Nikolayevich Tikhonov in 1950 and the French geophysicist Louis Cagniard. With advances in instrumentation, processing and modelling, MT has become one of the most important tools in deep Earth research.