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Joint analysis of GOCE gravity gradients data of gravitational potential and of gravity with seismological and geodynamic observations to infer mantle properties / Marianne Greff-Lefftz in Geophysical journal international, vol 205 n° 1 (April 2016)  

Public [article]  inGeophysical journal international > vol 205 n° 1 (April 2016) . - pp 257 - 283 Titre : Joint analysis of GOCE gravity gradients data of gravitational potential and of gravity with seismological and geodynamic observations to infer mantle properties Type de document : Article/Communication Auteurs : Marianne Greff-Lefftz, Auteur ; Laurent Métivier , Auteur ; Isabelle Panet , Auteur ; Lambert Caron, Auteur ; Gwendoline Pajot-Métivier , Auteur ; Johannes Bouman, Auteur Année de publication : 2016 Projets : TOSCA / Article en page(s) : pp 257 - 283 Note générale : bibliographie This study was supported by CNES (Centre National d’Etudes Spatiales) through the TOSCA committee and is IPGP contribution number 3701. Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale [Termes IGN] champ de pesanteur terrestre [Termes IGN] données GOCE [Termes IGN] facteur d'échelle [Termes IGN] gradient de gravitation [Termes IGN] manteau terrestre [Termes IGN] méthode de Monte-Carlo [Termes IGN] potentiel de pesanteur terrestre [Termes IGN] viscosité Résumé : (auteur) Joint analysis of the seismic velocities and geoid, gravity and gravity gradients are used to constrain the viscosity profile within the mantle as well as the lateral density variations. Recent ESA's Gravity field and steady-state Ocean Circulation Explorer measurements of the second-order derivatives of the Earth's gravity potential give new possibilities to determine these mantle properties. Using a simple mantle model and seismic tomography results, we investigate how the gravitational potential, the three components of the gravity vector and the gravity gradients can bring information on the radial viscosity profile and on the mantle mass anomalies. We start with lateral density variations in the Earth's mantle based either on slab history or deduced from seismic tomography. The main uncertainties are: for the latter case, the relationship between seismic velocity and density—the so-called density/velocity scaling factor—and for the former case, the variation with depth of the density contrast between the cold slabs and the surrounding mantle. We perform a Monte Carlo search for the viscosity and the density/velocity scaling factor profiles within the mantle, which allows to fit the observed geoid, gravity and gradients of gravity. We compute the posterior probability distribution of the unknown parameters, and find that the gravity gradients improve the estimate of the scaling factor within the upper mantle, because of their sensitivity to the masses within the upper mantle, whereas the geoid and the gravity better constrain the scaling factor in the lower mantle. In the upper mantle, it is less than 0.02 in the upper part and about 0.08–0.14 in the lower part, and it is significantly larger for depths greater than 1200 km (about 0.32–0.34). In any case, the density/velocity scaling factor between 670 and 1150 km depth is not well constrained. We show that the viscosity of the upper part of the mantle is strongly correlated with the viscosity of the lower part of the mantle and that the viscosity profile is characterized by a decrease in the lower part of the upper mantle (about 1020–2 × 1020 Pa s) and by an increase (about 1023–2 × 1023 Pa s) at the top of the lower mantle (between 670 and 1150 km). The viscosity of the mantle below 1150 km depth is well estimated in our Monte Carlo search and is about 1022–4 × 1022 Pa s. Numéro de notice : A2016--192 Affiliation des auteurs : LASTIG LAREG+Ext (2012-mi2018) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggw002 Date de publication en ligne : 16/02/2016 En ligne : https://doi.org/10.1093/gji/ggw002 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91843 [article]