Two-dimensional magnetotelluric modeling of the Sabalan geothermal field using MT2DInvMatlab inversion source codes
عنوان دوره: نوزدهمین کنفرانس ژئوفیزیک ایران
کد مقاله : 1497-NIGS
نویسندگان
عضو هیات علمی گروه مهندسی معدن
چکیده
A magnetotelluric (MT) survey in the frequency range of 0.002-320 Hz was carried out on southwestern of Sabalan geothermal region. Twenty eight soundings were conducted in the study area. Data along a profile crossing the hot springs with seven MT stations have been implemented for modeling and inversion. MT data were analyzed and modeled using MT2DInvMatlab inversion source codes and the method of finite elements (FEM) for forward modeling. Inversion parameters as an Input file and appropriate mesh blocks design should prepared before starting the modeling and inversion. MT2DInvMatlab software include topography file into a forward model for terrain effects compensation in the inversion process. After setting up the model parameter, 2D inversion of the Sabalan magnetotelluric data has been performed using smoothness–constrained least square methods with a spatially regularization parameter estimation. The ACB (Active Constraint Balancing) algorithm employed to stabilize the model. Both apparent resistivity and phase data has been used to have model with minimum misfit for TM mode data. The resulting model reveal the presence of a resistive cover layer (Cap-rock) underlain by an anomalous conductive layer and other geological structures such as fluid-filled faults in about 500-1000 m below the ground surface. A very low resistivity (3-5 ohm-m) feature at the depths below 2000 m, bounded by two more resistive (100-500 ohm-m) features that interpreted as the main reservoir of the geothermal system in the area. At shallow depths, the resistivity model obtained from the MT data is consistent with the general conceptual resistivity model proposed for high-temperature geothermal systems.
کلیدواژه ها
Title
Two-dimensional magnetotelluric modeling of the Sabalan geothermal field using MT2DInvMatlab inversion source codes
Authors
Gholam- Abbas Fanaee-Kheirabad
Abstract
A magnetotelluric (MT) survey in the frequency range of 0.002-320 Hz was carried out on southwestern of Sabalan geothermal region. Twenty eight soundings were conducted in the study area. Data along a profile crossing the hot springs with seven MT stations have been implemented for modeling and inversion. MT data were analyzed and modeled using MT2DInvMatlab inversion source codes and the method of finite elements (FEM) for forward modeling. Inversion parameters as an Input file and appropriate mesh blocks design should prepared before starting the modeling and inversion. MT2DInvMatlab software include topography file into a forward model for terrain effects compensation in the inversion process. After setting up the model parameter, 2D inversion of the Sabalan magnetotelluric data has been performed using smoothness–constrained least square methods with a spatially regularization parameter estimation. The ACB (Active Constraint Balancing) algorithm employed to stabilize the model. Both apparent resistivity and phase data has been used to have model with minimum misfit for TM mode data. The resulting model reveal the presence of a resistive cover layer (Cap-rock) underlain by an anomalous conductive layer and other geological structures such as fluid-filled faults in about 500-1000 m below the ground surface. A very low resistivity (3-5 ohm-m) feature at the depths below 2000 m, bounded by two more resistive (100-500 ohm-m) features that interpreted as the main reservoir of the geothermal system in the area. At shallow depths, the resistivity model obtained from the MT data is consistent with the general conceptual resistivity model proposed for high-temperature geothermal systems.
Keywords
Magnetotellurics, Geothermal exploration, reservoir, MT2DInvMatlab, Sabalan, Iran