TITLE:
2D TEM Modeling for a Hydrogeological Study in the Paraná Sedimentary Basin, Brazil
AUTHORS:
Emerson Rodrigo Almeida, Jorge Luís Porsani, Fernando Acácio Monteiro dos Santos, Cassiano Antonio Bortolozo
KEYWORDS:
Transient Electromagnetic (TEM), 2D Modeling, Hydrogeophysics, Paraná Basin, Brazil
JOURNAL NAME:
International Journal of Geosciences,
Vol.8 No.5,
May
27,
2017
ABSTRACT: This work uses 2D TEM (Transient Electromagnetic) modeling for a hydrogeological study in the Paraná sedimentary basin. The study area is located at the northern region of the state of São Paulo, Brazil, where groundwater is exploited from two aquifer systems: one sedimentary, shallow, and the other crystalline, deep. The interest in applying the TEM method in this area owes to the high exploitation rates of groundwater from the crystalline aquifer system for irrigation, which is triggering considerable seismic activity locally. This aquifer system is composed of fractured basalt within the Serra Geral Formation and is about 120 m deep. Eighty-six TEM soundings were acquired at this location, but in nine cases the data did not fit the modelled curve for 1D geoelectrical models due to the geological complexity of the area. This paper shows 2D geoelectrical modeling results based on the FDTD (Finite Differences in Time Domain) method to explain the lateral resistivity variation within the geological setting. A 2D model was generated for each sounding and compared with 1D inversion models as well as with direct information from wells. The results show some vertical variations of about 10 to 30 meters on the upper interface of the basalt layer from Serra Geral Formation. They are located at approximately 60 meters from the center of the soundings. The existence of these 2D structures in the subsurface can be related to the drainage system in the study area. The presence of these structures may indicate a connection between the shallow and deep aquifer systems, acting like a conduit that may contribute to the seismic activity reported.