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. / Den radio magnetotelluriska (RMT) metoden har sitt ursprung i (Tikhonov, 1950) och (Cagniard, 1953) arbete där strukturen hos geologisk resistivitet uppskattas med hjälp av naturligt förekommande elektriska jordströmmar. Detta genom att mäta den elektromagnetiska vågimpedansen vid markytan. Sedan använder (Paal, 1965) sig av elektromagnetiska planvågor från lågfrekventa radiosändare (10 − 30kHz), som artificiellt inducerar jordströmmar, för att uppskatta resistiviteten i mer ytligt underliggande geologisk struktur. Det är således källan till den inducerade jordströmmen som namngett RMT-metoden. Det är sedan påvisat av (Bastani,2001) att man kan använda sig av frekvenser i ett bredare spektrum (10 − 250kHz) för att få ökad vertikal upplösning. Slutligen påverkar frekvensen hos den elektromagnetiska vågen inträngningsdjupet och på så sätt tillåts det att uppskatta resistiviteten vid ett särskilt djup. I denna studie har en databehandlingsalgorithm utvecklats, baserat på arbete utfört av (Bastani, 2001), som bearbetar RMT fältdata. Impedans och resistivitet samt andra storheter beräknas för att sedan kunna exporteras och användas i existerande modelleringsprogramvara. Programvaran är skriven i matlab, och dess funktionalitet har prövats med syntetisk data samt data från Blötberget, Sverige. Även påverkan av olika processparametrar har undersökts. Detta har gjorts med framgång, men arbete återstår för att fullständigt verifiera korrekt implementering då utrustningen som användes för insamling av fältdata vid Blötberget felade. Därför kan kalibreringsproblem i programvaran inte helt uteslutas.

In this thesis, four studies using different geophysical electromagnetic methods are presented. In the first study dealing with airborne measurements, the noise response due to the rotation of the aircraft and the aircraft itself as a metallic conductive body on the Earth's electromagnetic response in very low frequency and low frequency band was investigated. The magnetic fields are independent of the aircraft in the VLF band and part of the LF band. But at higher frequencies (above 100 kHz), the signals are more influenced by the aircraft. The aircraft also generates its own noise frequencies which are mixed with the radio transmitter signals. The second and third studies are applications of radio-, controlled source-magnetotellurics and electrical resistivity tomography methods at a quick-clay landslide site in southwest Sweden. The data are processed and modeled in 2D and 3D, and the models are compared with high-resolution seismic and geotechnical data. The obtained results were further validated and refined by performing synthetic tests in the second study. The third study shows that the 3D models provide larger and more continuous volume of the quick clay structure than traditional 2D models. Both studies have shown that integrated application of geophysical methods for landslides is ideal. Quick clays often overlie the coarse-grained layers showing an increase of resistivity values in the models. In the fourth study, a new audio magnetotelluric data acquisition technique is developed and is named moving magnetotellurics (MMT). In this new technique, the magnetic sensors are placed on the ground and only 15 to 20 minutes data are acquired for each station, which usually is enough to cover the frequency range 30-300 Hz. The new technique is more efficient and convenient than the traditional magnetotelluric method, and test measurements have shown that it is an applicable method in shallow depth studies.

Radio magnetotellurics (RMT), crosshole ground penetrating radar (GPR), and crosshole electrical resistance tomography (ERT) were applied in a range of hydrogeological applications where geophysical data could improve hydrogeological characterization. A profile of RMT data collected over highly resistive granite was used to map subhorizontal fracture zones below 300m depth, as well as a steeply dipping fracture zone, which was also observed on a coinciding seismic reflection profile. One-dimensional inverse modelling and 3D forward modelling with displacement currents included were necessary to test the reliability of features found in the 2D models, where the forward models did not include displacement currents and only lower frequencies were considered. An inversion code for RMT data was developed and applied to RMT data with azimuthal electrical anisotropy signature collected over a limestone formation. The results indicated that RMT is a faster and more reliable technique for studying electrical anisotropy than are azimuthal resistivity surveys. A new sequential inversion method to estimate hydraulic conductivity fields using crosshole GPR and tracer test data was applied to 2D synthetic examples. Given careful surveying, the results indicated that regularization of hydrogeological inverse problems using geophysical tomograms might improve models of hydraulic conductivity. A method to regularize geophysical inverse problems using geostatistical models was developed and applied to crosshole ERT and GPR data collected in unsaturated sandstone. The resulting models were geologically more reasonable than models where the regularization was based on traditional smoothness constraints. Electromagnetic geophysical techniques provide an inexpensive data source in estimating qualitative hydrogeological models, but hydrogeological data must be incorporated to make quantitative estimation of hydrogeological systems feasible.