Applied electromagnetic methods for geothermal exploration in northern México: 3D forward and inverse modeling of Magnetotelluric data

The main focus of this thesis is the application of electromagnetic (EM) methods for the exploration of geothermal resources in San Felipe's area, which it is located in northern Mexico. A regional geophysical field survey was carried out in 2014 where Magnetotellurics (MT) and Transient Electromagnetics (TEM) methods were applied. Conventional 1D inversion techniques are firstly performed to the TEM data. Afterwards, a Spatially Constrained Inversion (SCI) scheme is applied to the TEM data and thus, a pseudo-3D resistivity model of the shallow part of San Felipe's subsurface is achieved. The acquired MT data are processed with robust statistics techniques. The effect of the static shift in MT data is corrected based on the TEM information. Prior to the inversion of the MT data, 3D MT modeling studies are carried out to investigate the influence of the field survey configuration applied in San Felipe. Later on, one-dimensional inversions of MT data are carried out and the uncertainty of the inverse models is evaluated. To perform a 3D inversion of San Felipe MT data, trials are firstly performed by systematically varying the input parameters and their impact on the inversion models is appraised. The derived TEM information is incorporated into the 3D MT inversion scheme to stabilize the inversion process. On the one hand, a 3D MT constrained inversion model is achieved using the information of TEM inversion models as constraints. On the other hand, the features from the pseudo-3D resistivity model generated with the SCI of TEM data is incorporated as a priori information into the 3D inversion scheme of MT data. The second approach shows better results and therefore its output is taken as the preferred inversion model. A conductive structure is imaged in the central part of the survey area which is interpreted as a sedimentary basin at its shallow part and as a fault zone with geothermal fluids at depths greater than 1.5 km.