Moho determination from GOCE gradiometry data over Ethiopia

Abstract

The gravity field and steady-state ocean circulation explorer (GOCE) satellite mission has a good global coverage of data except across the Polar Regions. Here, the goal is to take the advantage of such a coverage over Ethiopia and use the 2nd order radial derivative of the Earth's gravitational potential for determining a Moho model for this territory. In order to compute Moho depth, we used the Vening Meinesz-Moritz (VMM) theory of isostasy and the GOCE 2nd order radial derivatives are inverted using an integral equation in combination with effects of topographic/bathymetric, sediment and consolidated crystalline masses and considering density contrast model derived from CRUST1.0. The GOCE derived Moho depth over Ethiopia varies from 24.9 to 44.8 km. More specifically, the Moho depth ranges outside of the rift valley from 33.9 to 44.4 km and from 25.5 to 44.8 km across the western and eastern plateaus of Ethiopia respectively. In addition, inside the main Ethiopian rift system the Moho depth varies from 24.9 to 41.5 km where the minimum occur in the Afar region. We compare our Moho model with that of CRUST1.0, Meier 05, M13_Eurasia, GEMMA models and 82 local seismic stations over Ethiopia. The result showed, respectively, standard deviations of 5.3, 4.9, 8.1, 5.0 and 4.0 km with respect to these Moho models. Our Moho model is closer to the local seismic stations than other models.