 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.Since first being created in the 1950s, magnetotelluric sensors, receivers and data processing techniques have followed the general trends in electronics, becoming less expensive and more capable with each generation.