Three-dimensional inversion of gravity data from the main Ethiopian Rift

The crustal thickness distribution beneath the Main Ethiopian Rift is determined using a 3-D inverse approach to gravity data interpretation. The depths to the crust-upper mantle interface form the inversion parameters. These initial model parameters are constrained with the results of the seismic refraction experiment of the region. The degree of ambiguity of the final model parameters is then quantified using a Q-mode factor analysis approach. The results of the modelling indicate a strong crustal attenuation zone (less than or equal to 31 km) closely associated with the rifting of the graben and an abrupt fall of the Moho interface on either side of the rift (51 km) related to the formation of the western and southeastern plateaus. However, no indication of crustal separation is observed. The semi-quantitative ambiguity analysis reveals the association of the model parameters from the southeastern plateau with the strong ambiguity region. These model parameters represent the depths to the Moho interface where the seismic control is relatively less. (C) 2000 Elsevier Science Limited. All rights reserved.