Moho Geometry Estimation Beneath the Gulf of Guinea From Satellite Gravity Data Based on a Regularized Non-Linear Gravity Inversion

In this work, we present a new gravimetric Moho model over the Gulf of Guinea computed from the inversion of the global gravity EIGEN-6C4 model. The computation procedure contains a regularized non-linear inversion algorithm. Before applying the inversion algorithm, the gravity data from the EIGEN-6C4 model have been corrected from gravimetric effects of topography, bathymetry, and sediments. To calculate these corrections, a forward modeling has been applied using tesseroids to take into account the earth curvature, and via the Legendre Quadrature integration technique. The inversion procedure of the Bouguer disturbances integrates the use of hyperparameters in particular the regularization parameter, the anomalous Moho density contrast and the reference Moho depth. This regularized non-linear inversion method has been tested on synthetic data contaminated by a normally distributed noise. Through this test, the inversion method showed its effectiveness in estimating a Moho model. The application of this method on the Gulf of Guinea has produced a high-resolution gravimetric model, whose depths vary between 7.75 and 44.50 km. The greatest depths (greater than 40 km) are located along the eastern part of the study area. The comparison of our gravimetric model with the isostatic Airy, GEMMA (GOCE Exploitation for Moho Modeling and Applications) and CRUST1.0 Moho models, globally shows good similarities. The comparison of our gravimetric Moho model to the GEMMA gravimetric model exhibits large residuals around the continental margin, thus reflecting the limit of the inversion method for areas with great Moho depth gradients. The differences observed between our gravimetric model and the CRUST1.0 model in certain regions such as southern Nigeria show the impact of the neglect of anomalous crustal and mantle sources in the accuracy of the solutions obtained after inversion. However, our gravimetric model yields an improved and high-resolution representation of the Moho undulations over the Gulf of Guinea compared to previous gravimetric Moho models.