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ABSTRACT: This study aimed at a better knowledge of aquifers of fractures of Bondoukou region (north-east of Côte d'Ivoire) by making a map of geological formations and structures from satellite Landsat 7 imagery. The techniques of images merging (Selective Principal Components Analysis, RGB encoding, the index-calculus and the tri-color additive synthesis) allowed to identify and map geological formations those constitute paleoproterozoic field of Bondoukou region. The use of spatio-directionnel filtering methods of Sobel and gradient has led to develop detailed map of lineaments. This map includes about 5000 fractures. The study of fracturing intensity raises the character much fractured of Bondoukou region notably in the north and south parts. The contact area between the prophyroid granodiorite and the volcano-sedimentary domain with strong structural tendency was also highlighted. The analysis of fracture networks reveals that the distribution of the lengths of fractures follows the power law. This law indicates that the fracture networks of Bondoukou region would have reached its optimal stage. The values of spacing of fractures fit better to the gamma law. The modelling all azimuths underlines a probability of more than 62% to meet a fracture within one kilometer of distance. The analysis of the induced permeability permits to identify the main corridors of circulation and concentration of groundwaters. These corridors are strongly in relation with the drainage network with which they are more or less superimposed. This state lets suppose an easy recharge of fractured aquifers of Bondoukou region.
KEYWORDS: Fractured aquifers, Landsat 7 imagery, images merging, filtering methods, power law, gamma law, induced permeability, Côte d'Ivoire.
RESUME: Cette étude avait pour objectif une meilleure connaissance des aquifères de fractures de la région de Bondoukou (nord-est de la Côte d'Ivoire) par la cartographie des formations et structures géologiques effectuée à l'aide des image Landsat 7. Les techniques de fusion d'images (l'Analyse en Composantes Principales Sélectives, le codage RVB, le calcul des indices et la synthèse trichromique additive) ont permis la mise en évidence et la cartographie des grandes formations géologiques qui forment le domaine paléoprotérozoïque de la région de Bondoukou. L'utilisation des méthodes de filtrage spatio-directionnel de Sobel et gradient a abouti à l'élaboration de la carte linéamentaire détaillée. Celle-ci comporte environ 5000 fractures. L'étude de l'intensité de la fracturation relève...