f Directional noise cancelling in magnetotellurics

In Magnetotelluric (MT) data processing, poor signal-to-noire ratio usually biaces the impedance tensor Z elements estimates. Strong electromagnetic (EM) noise may thus render the MT method impracticable in industrial areas. Noise due to periodic sources (i.e. power line harmonies) is easily removed by analog filtering in the field; but non-periodic EM noise (see e.g. Szarka, 1988, for an exhaustive list) should be handled more accurately in MT data processing.