Aplicacion Del Metodo Magnetotelurico En El Anticlinal Ingre Del Subandino Boliviano

Structural interpretation in Subandean fold-and-thrust belts has many uncertainties, especially when the seismic image is not adequate. In order to improve the geologic interpretation of the Ingre Structure in Bolivia the magnetotelluric (MT) method was applied. The method determines the resistivity distribution of the subsurface from measurements of naturally occuring electric and magnetic fields. The studied subandean structure is formed by a surface anticline, with a Carboniferous nucleus, and a deep Silurian-Devonian anticline, detached from the former by Upper Devonian rocks tectonically piled-up. The objective of this study was to obtain the structural image of Paleozoic formations at 3500-5000 mbgl. The information available in the area consisted of surface data and a strike seismic line of poor quality. MT data was acquired over five lines perpendicular to the structure, forming a non uniform grid. The first processes were ‘blind’ 2D and 3D inversions, without any geologic control. In these, conductive zones could be separated from a resistive core that corresponds to the deep anticline. 2D inversions controlled by geological models were also performed. These allowed the feasibility of different models and the method’s sensibility to be tested.