A comparison of GOCO05c satellite data to synthetic gravity fields computed from 3D density models in ASPECT

Abstract

One of the limitations of geodynamical modelling of the Earth’s mantle nowadays is the absence of a reliable density model. This research uses scaled seismic tomography models in combination with crustal model CRUST1.0 to obtain a global density model. Through geodynamical finite element code ASPECT the gravity fields of these models are calculated and tested against the Earth’s gravity field from satellite data (GOCO05c). Spectral filtering with spherical harmonics decomposition software is applied to investigate whether contributions from the Earth’s mantle can be isolated. The long-wavelength gravity field obtained from CRUST1.0 seems to be a first-order estimate of the smooth parts of the Moho topography. However, including the mantle into the gravity models presents obstacles in the form of model resolution. Due to computational limitations, the gravity signals of the tomographic models do not completely converge. When merging crustal and tomographic data, the resolution of tomographic models prove insufficient in the upper part of the model and cause high-amplitude density jumps in the lithosphere. Neither the gravity signals of the tomographic models nor the gravity signals of the composite models correlate to GOCO05c in any spectral range. High-resolution topography of large density contrasts such as the lithosphere-astenosphere boundary, transition zone discontinuities and the CMB must be incorporated in order to achieve a more realistic gravity field and subsequently allow for the investigation of density perturbations in the mantle.