• Miranda, J.
• Santovaia, H.
• Silva, R.
• Moura, R.

Abstract

The present work shows some results obtained by the Time-Domain Electromagnetic Method (TDEM) to help characterize the geology and Penacova- Régua-Verin fault structure in the Vila Pouca de Aguiar sector. The Fault is an important tardi-variscan structure with NNE-SSW direction, more than 500 km long, extending from the North of Spain until near Nazaré. The application of the TDEM method aimed to acquire data towards obtaining profiles of subsurface electrical resistivity in the zone affected by the fault and adjacent terrain. Electrical resistivity profiles, resulting from the combination of individual soundings, were performed in the SW quadrant of 6D-Vila Pouca de Aguiar of Carta Geológica de Portugal sheet, at a scale of 1/50 000, along Penacova-Régua-Verin Fault and perpendicularly, with WNW-ESE orientation, in the western sector of the fault. Some confirmation and preliminary models were accomplished using the results obtained by other authors, allowing to verify the validity of the obtained inverted data. The method responded in accordance with the conceptual model but allowed the additional distinction between alteration zones and apparently identical lithologies. Overall, three main blocks were identified, the most superficial shows high resistivities and low thickness. The second block has lower resistivity values due to the influence of the water level at this depth. In the third block, more oscillatory characteristics were identified throughout the various surveys. Although, in general, its high thickness and high values of electrical resistivity were highlighted. However, one of the obstacles in the implementation of the method was the presence of wind farms in Northern Portugal, bridges, metal fences, as well as power lines and high voltage pylons that produce electromagnetic noise and thus interfere with the readings obtained.

Topics

• impedance spectroscopy
• resistivity