Sensitivity analysis of gravity gradient inversion of the Moho depth—a case example for the Amazonian Craton
We present a novel approach for linearized gravity inversion to estimate the Moho depth, which allows the use of any gravitational component instead of the vertical gravity component only. The inverse problem is solved with the Gauss-Newton algorithm and the gravitational field of the undulating Moho depth is calculated with tesseroids. Hereby, the density contrast can be laterally variable by using information from seismological regionalization. Our approach is illustrated with a synthetic example, which we use to explore different regularization parameters. The vertical gravity gradient gzz provides the most reasonable results with appropriate parameters. As a case example, we invert for the Moho depth of the Amazonian Craton and its surroundings. The results are constrained by estimates from active seismic measurements. Our new Moho depth model correlates to tectonic domains and is in agreement with previous models. The estimated density contrasts of the tectonic domains agree well with the lithospheric architecture and show with 300-450 kg m-3 lower density contrasts for continental domains, whereas the oceans reveal a density contrast of 450-500 kg m-3. The wider range of estimated density contrast for the continent reflects uncertainties in Precambrian Fold Belts that arise from its small gravity signal. Our results demonstrate that a variable density contrast at the Moho depth is a valuable enhancement for gravity inversion.