Spectral harmonic analysis and synthesis of Earth’s crust gravity field

We developed and applied a novel numerical scheme for a gravimetric forward modelling of the Earth’s crustal density structures based entirely on methods for a spherical analysis and synthesis of the gravitational field. This numerical scheme utilises expressions for the gravitational potentials and their radial derivatives generated by the homogeneous or laterally varying mass density layers with a variable height/depth and thickness given in terms of spherical harmonics. We used these expressions to compute globally the complete crustcorrected Earth’s gravity field and its contribution generated by the Earth’s crust. The gravimetric forward modelling of large known mass density structures within the Earth’s crust is realised by using global models of the Earth’s gravity field (EGM2008), topography/bathymetry (DTM2006.0), continental icethickness (ICE-5G), and crustal density structures (CRUST2.0). The crust-corrected gravity field is R. Tenzer(B) · V. Gladkikh National School of Surveying, University of Otago, Box 56, 310 Castle Street, Dunedin, 9054, New Zealand e-mail: [email protected] P. Novák Department of Mathematics, University of West Bohemia, Univerzitní 22, Plzeň, Czech Republic P. Vajda Geophysical Institute, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, Slovak Republic Hamayun Delft Institute of Earth Observation and Space Systems (DEOS), Delft University of Technology, Kluyverweg 1, Delft, The Netherlands obtained after modelling and subtracting the gravitational contribution of the Earth’s crust from the EGM2008 gravity data. These refined gravity data mainly comprise information on the Moho interface and mantle lithosphere. Numerical results also reveal that the gravitational contribution of the Earth’s crust varies globally from 1,843 to 12,010 mGal. This gravitational signal is strongly correlated with the crustal thickness with its maxima in mountainous regions (Himalayas, Tibetan Plateau and Andes) with the presence of large isostatic compensation. The corresponding minima over the open oceans are due to the thin and heavier oceanic crust.