3-D inversion of MT data from the Sabalan geothermal field, Ardabil, Iran
2013; Elsevier BV; Volume: 93; Linguagem: Inglês
10.1016/j.jappgeo.2013.03.006
ISSN1879-1859
AutoresReza Ghaedrahmati, Ali Moradzadeh, Nader Fathianpour, Seong Kon Lee, Soheil Porkhial,
Tópico(s)Seismic Waves and Analysis
ResumoSince the true Earth is 3-D in nature, a three-dimensional (3-D) inversion has clear advantages over lower dimensional inversions. We utilized a 3-D magnetotelluric (MT) inversion code, WSINV3DMT, to obtain a realistic resistivity model using a long period MT data set collected in the Northwest Sabalan geothermal field in Ardabil, Iran. The apparent resistivity and phase curves, the magnetic induction vectors, the impedance polar diagrams and the rotational invariant of impedance tensor, indicate a complex 3-D conductivity structure. After setting up the model parameters and designing the appropriate block discretization, we performed the 3-D inversions for two sets of observed data; one set includes the full MT impedance tensor and another set contains only off-diagonal elements of the MT impedance. The final model was selected according to the relative magnitude of the data misfit and the model norm with respect to various Lagrangian multipliers. The results of this study illustrate the 3-D inversion of the off-diagonal elements of MT impedance tensor is precisely enough to explain the structures related to the geothermal source. The obtained results were compared with the results of available 2-D models and they are then interpreted using all of the geological and drilling data of the area. The main outcome of this study is the precise delineation of the geometry of geothermal source that is located at the center of the study area with a surface coverage of about 7 km2.
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