Determination of gravity and isostatic Moho: Implications for the evolution of rifting in the central Main Ethiopian Rift

ABS T R A C T We use gravity anomalies derived from GGMplus2013 gravity accelerations to generate a Moho undulation map of the Main Ethiopian Rift (MER) and surrounding plateau. The regional Bouguer anomaly is estimated by applying a low pass filters to different cutoff wavelengths and the resulting anomaly map is inverted using Parker Oldenburg method to generate a gravity Moho map. The isostatic Moho is computed using Airy model. Our results show that gravity Moho is in agreement with previous receiver function studies in the region. Based on the results on gravity and isostatic Moho, we estimate the magnitude and orientation of the vertical stress in the rift and surrounding region. In general, the vertical stress agrees very well with the regional tectonic and geomorphic features, where present day rifts are characterized by negative vertical stress except the central MER, which is characterized by positive stress. We argue that the crust in the central MER is in a state of isostatic adjustment. Our study provides an alternative explanation for why the central MER is less developed compared to the northern MER.