Three dimensional inversion of gravity data from the Main Ethiopian Rift

A three-dimensional interpretation of the newly compiled Bouguer anomaly ma p of the Main Ethiopian Rift is discussed. Then, the crustal thickness dist ribution beneath the Main Ethiopian Rift is confirmed using a 3-dimensional inverse approach to gravity data interpretation. The depths to the crust-u pper mantle interface form the inversion parameters. Both approaches are co nstrained with the results of the seismic refraction experiments of the reg ion. The degree of ambiguity of the final model parameters is then quantifi ed. The Bouguer anomalies along the axial portion of the rift floor, as deduced from the results of the regional and residual separation, are mainly cause d by deep-seated structures. The high resolution 3-D forward modeling revea ls a possible crustal thickness and density distribution beneath the graben . The results of the inversion confirm a strong crystal attenuation zone (les s 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 (up to 51 km) related to the formation of the western and southeastern plateaus. However, no indication of crustal separation is observed. The ambiguity analysis reveals that greater ambiguity of the model paramete rs exists in the southeastern plateau. There, these model parameters repres ent the depths to the Moho interface where the seismic control is relativel y less. (C) 2000 Elsevier Science Ltd. All rights reserved.