| Summary: | The TEM (Transient Electro Magnetic) and MT (MagnetoTelluric) methods are commonly used in geothermal exploration. The resistivity structure of the geothermal systems may be used to gain information about the temperature and other attributes of interest. Measurements have traditionally been inverted in 1D, but advances in multidimensional inversion enable routine 3D inversions of MT data in geothermal exploration. The main objectives of this study is to investigate the inversions done for geothermal exploration. Special attention is given to the problem of static shift, that arises in MT soundings when there is inhomogeneous surface resistivity. Both synthetic data from a synthetic geothermal system with different varying surface resistivity and real data from the Hengill geothermal area are used. For all the data, joint 1D inversions of the TEM and MT data and 3D inversions of MT data without and with static shift correction, are done. The resulting models for all the inversion are compared and the results are discussed in terms of the effectiveness of the methods. The results reveal that 3D models of the resistivity interpolated from joint 1D inversion of TEM and MT data, recover near surface resistivity structure fairly well but at depth become inaccurate. Models from 3D inversion fare better overall, recovering resistivity structures with good accuracy at all depths. The difference of models from 3D inversion of MT without and with static shift correction, is not great but correcting the static shift prior to inversion results in somewhat better models. The setup of the inversion is shown to play an important role in the resulting models. Using a different mesh and/or selecting different frequencies affects the resolution, time and the details of the inversion. It is therefore crucial to be critical of the inversion results and test the results with multiple inversions and/or forward modeling before interpretation. TEM og MT mælingar eru gjarnan notaðar við jarðhitarannsóknir. Unnt er að nota viðnáms gerð ...
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