Developing data processing program for a new radio magnetotelluric (RMT) instrument

Abstract: The radio magnetotellucic (RMT) method originates from (Tikhonov, 1950) and (Cagniard,1953) who discovered the possibility to estimate resistivity in the Earth’s subsurface using naturally occurring telluric currents. This through measuring the surface impedance of electromagnetic waves. Later (Paal, 1965) makes use of electromagnetic plane-waves originating from radio transmitters that operates in the very low frequency range (10 − 30kHz). These plane waves artificially induce telluric currents which can then be used to estimate resistivity in shallow subsurface. It is hence the source of the electromagnetic wave inducing the telluric current that named the RMT method accordingly. It’s then shown by (Bastani, 2001) that the signal can be measured in an even broader band (10 − 250kHz) to gain a better vertical resolution. Finally, frequency of the electromagnetic wave is affecting the skin depth and one can therefore estimate the depth of resistivity layers in the subsurface. In this thesis a data processing algorithm has been developed, based on the work in (Bastani, 2001), that processes RMT field data. Impedance, resistivity among other quantities is calculated. One can then export this data and use it in existing modeling software. New processing parameters has been implemented and its effect on the data set investigated. The software is implemented in matlab, and tested with synthetic data and data measured at Blötberget, Sweden. However, work is still to be done due to field equipment malfunction during measurements at Blötberget. This rendering an, at least partly, faulty data set. Therefore one cannot completely exclude calibration issues until a clean data set is taken.