This paper comprises geophysical studies carried out with the resistivity method in the Porto Seguro region, in the state of Bahia (Brazil). The objective was to find the main aquifer of that region. The work was performed on a area of approximately 60 km² located north of the Porto Seguro city. The studied area has sedimentary units with Tertiary (Formação Barreiras) and Quaternary (coastal shore) ages. Sixty vertical electrical soundings (VES) were performed using the Schlumberger array: 14 for regional reconnaissance; 36 for detailed study and 10 in a profile between the cities of Eunápolis and Porto Seguro. The VES in the regional profile were carried out to define the basement topography between these cities. A Fortran program was written for the quantitative interpretation of the VES, based on the method that uses the linearized inversion with multiple weight for the deviations (LIMWD). This proposition was tested on synthetic VES data and then it was used with field data. The results showed that this method is more stable and powerful than the traditional linearized inversion method which uses L¹ and L² fixed norms. The available information about well drilling data of the region was used to aid the interpretation. Geoelectrical sections were drawn from the inverted results of the thickness and resistivity of the layers. The interpretation of these sections provided the definition of the main aquifer for ground water exploitation in this region. This aquifer is confined to saturated sandstone layer in the mid-north portion of the area at about 80 m deep and an average thickness of 70 m. This aquifer represents the best option for ground water exploitation to supply the city of Porto Seguro.
Electro-resistivity survey; VES inversion; Aquifer mapping; Porto-Seguro city
