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Auteur Jean Besse |
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Dynamic mantle density heterogeneities and global geodetic observables / Marianne Greff-Lefftz in Geophysical journal international, vol 180 n° 3 (March 2010)
[article]
Titre : Dynamic mantle density heterogeneities and global geodetic observables Type de document : Article/Communication Auteurs : Marianne Greff-Lefftz, Auteur ; Laurent Métivier , Auteur ; Jean Besse, Auteur Année de publication : 2010 Note générale : bibliographie Langues : Anglais (eng) Résumé : (auteur) We investigate the influence of mantle dynamics on low degree deformations of the Earth at geological timescale. We first compute surface deformations, and discuss the analytical form of the tangential surface displacement induced by internal loads, in a reference frame related to the centre of mass of the planet. We use the theoretical Love numbers formalism since the Earth has a viscoelastic behaviour at geological timescale. Then we quantify degree-one and degree-two deformations induced by upwelling domes and subducted plates sinking into the mantle. We use a simple model in which the slabs are modelled as blobs diving vertically through the mantle, and in which the domes are assumed to be stable over the last 120 Ma. Their location is modelled from seismic tomography within the lower mantle. The temporal evolutions of the J2 gravitational potential coefficient and of the geocentre motion are plotted since 120 Ma. We find that:
(1) The mantle density heterogeneities within the mantle can explain the present-day non-hydrostatic flattening of the Earth. However they vary at a too slow timescale to significantly perturb the graphic coefficient.
(2) Although there is a significant discrepancy of about a few hundred metres between the centre of figure and the centre of mass of the Earth, the secular variation of the geocentre motion is one order of magnitude smaller than the one induced by surface loads.Numéro de notice : A2010-628 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2009.04490.x En ligne : https://doi.org/10.1111/j.1365-246X.2009.04490.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95911
in Geophysical journal international > vol 180 n° 3 (March 2010)[article]Rotational bulge and one plume convection pattern: Influence on Martian true polar wander [short paper] / Hélène Rouby in Earth and planetary science letters, vol 272 n° 1-2 (30 July 2008)
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Titre : Rotational bulge and one plume convection pattern: Influence on Martian true polar wander [short paper] Type de document : Article/Communication Auteurs : Hélène Rouby , Auteur ; Marianne Greff-Lefftz, Auteur ; Jean Besse, Auteur Année de publication : 2008 Article en page(s) : pp 212 - 220 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Termes IGN] Mars (planète)
[Termes IGN] mouvement du pôle
[Termes IGN] Rotation de planèteRésumé : (auteur) Motion of the entire solid planet with respect to its spin axis have been proposed on Mars. This movement is known as True Polar Wander (TPW). According to the conservation of angular momentum with no external torque, on geological time scales the axis of maximum inertia of a planet is aligned with the rotation axis. Then rearrangement of masses within the mantle disturbs the planet's inertia and induces TPW. The convection pattern on Mars is possibly controlled by a sequence of single plumes originating from the core-mantle boundary. Using a homogeneous model of the martian mantle and modelling the plume as a sphere, we calculate the inertial tensor perturbations caused by the plume mass anomaly. We investigate the stabilizing influence of the remnant rotational bulge due to the lithosphere elasticity on these perturbations. It appears that, during early martian history, the elastic lithosphere was thin enough to allow its fractures under the inertia perturbations induced by a hot plume. Consequently, the lithosphere's behaviour became effectively viscoelastic and the plume could induce large TPW. We conclude that one plume convection pattern should have greatly influenced the rotation pole behaviour during early Mars history: around 4 Gyr ago, Mars already could have experienced two TPW events lasting possibly only a few million years each. We then compare our scenario with others already published in the literature. Numéro de notice : A2008-637 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.epsl.2008.04.044 En ligne : https://doi.org/10.1016/j.epsl.2008.04.044 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103442
in Earth and planetary science letters > vol 272 n° 1-2 (30 July 2008) . - pp 212 - 220[article]