What is the smallest change caused by geothermal fluids at depth that can be seen from magnetotelluric monitoring?

Hugo Larnier1, Pascal Sailhac2, Abdelfettah Yassine1,3 and Eva Schill4, (1)Institut de Physique du Globe Strasbourg, Strasbourg Cedex, France, (2)CNRS, Paris Cedex 16, France, (3)Karlsruhe Institute of Technology, Karlsruhe, Germany, (4)Karlsruhe Institute of Technology, Institute of Nuclear Waste Disposal (INE), Karlsruhe, Germany