Contribution to the Investigation of Structure and Origin of a Rift Valley System by Gravimetry

Geophysical data have real interest only after a series of treatments; prior to be more useful, the diurnal, annual, semi annual and secular variations must be at least eliminated from the magnetic data. The same way for gravity data, they become particularly significant after a series of corrections, where the latitude, altitude, topographic and tidal influence of the sun and moon, all have been eliminated. After undergoing these corrections commonly called data reductions, the data are located with respect to geoid. These reductions processes need first to adopt the work frame hypothesis concerning the mode of calculation and the depth compensation. For our investigation measurements have been done in the East of Democratic Republic of Congo including the graben region from the parallel joining Goma city and Mahagi city, the region between Albert and Aka lakes and the route from Aba to Kinsagani. During the surveys the density of recording points has been selected according to the importance of anomalies. In this way, the offset was 1 km where the disturbance was high in Goma city and 20 km have been sufficient along the route from Aba to Kinsagani. The compensation hypotheses used are: Pratt 113.7,80 and 50 km, Airy 60, 40, 50 and 20 km.