Contribution of Gravimetry to the hydrogeological recognition of the area of Wadi Righ –Ouargla

Gravimetry is a geophysical methods often used in oil exploration and mining research but rarely in the hydrogeological field, the aim of this work is to exploit the gravimetric data to develop a structural model of the region of Oued Righ - Ouargla has less than 1,000 m depth and perform a litho-stratigraphic modeling of subsurface formations to assess the ability of a karst formation of the terminal complex water table (Eocene Senonian). Multiple filtrations and signal processing techniques for gravimetric datas were operated such as the Euler Déconvolution, the analytical signal and the horizontal gradient. The results were used to evaluate the potential of karstification in the area and to model the phenomenon; the subsurface structural mapping has also led to the relationship between the well productivity and network of faults and fractures.Key words: Euler deconvolution, analytic signal, faults, kars

Use of geophysical methods for the demonstration of Karstic phenomena in southern Algeria: Guerraraarea (district of Ghardaïa. Algeria)

Karst and pseudo-karst result from natural phenomena associated with the circulation of water through soluble geological environments, causing subsidence, sinkholes, cavities and collapses. During the last five years, Guerrara area (southern Algeria) was the subject of multidisciplinary studies to characterize the geological formations and assess the impact of their distribution on the movement of water surface and deep aquifers.This study undertaken in three sites from the Guerrara area aims at the recognition and the characterization of underground voids (size, extension) by geophysical methods such as vertical electrical soundings and electrical tomography combined with 2D electromagnetic imaging ground penetrating radar GPR.Keywords: Pseudo-karst, sinkholes, Collapses, Ground penetrating radar, Cavitie