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Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations / M. Hayn in Geophysical journal international, vol 189 n° 3 (June 2012)  

Public [article]  inGeophysical journal international > vol 189 n° 3 (June 2012) . - pp 1430 - 1456 Titre : Wavelet‐based directional analysis of the gravity field : evidence for large‐scale undulations Type de document : Article/Communication Auteurs : M. Hayn, Auteur ; Isabelle Panet , Auteur ; Michel Diament , Auteur ; Matthias Holschneider, Auteur ; Mioara Mandea, Auteur ; Anne Davaille Année de publication : 2012 Article en page(s) : pp 1430 - 1456 Note générale : Bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] données GRACE [Termes IGN] manteau terrestre [Termes IGN] modèle de géopotentiel [Termes IGN] ondelette d'Abel-Poisson [Termes IGN] Pacifique (océan) [Termes IGN] subduction [Termes IGN] transformation en ondelettes Résumé : (Auteur) In the eighties, the analysis of satellite altimetry data leads to the major discovery of gravity lineations in the oceans, with wavelengths between 200 and 1400 km. While the existence of the 200 km scale undulations is widely accepted, undulations at scales larger than 400 km are still a matter of debate. In this paper, we revisit the topic of the large‐scale geoid undulations over the oceans in the light of the satellite gravity data provided by the GRACE mission, considerably more precise than the altimetry data at wavelengths larger than 400 km. First, we develop a dedicated method of directional Poisson wavelet analysis on the sphere with significance testing, in order to detect and characterize directional structures in geophysical data on the sphere at different spatial scales. This method is particularly well suited for potential field analysis. We validate it on a series of synthetic tests, and then apply it to analyze recent gravity models, as well as a bathymetry data set independent from gravity. Our analysis confirms the existence of gravity undulations at large scale in the oceans, with characteristic scales between 600 and 2000 km. Their direction correlates well with present‐day plate motion over the Pacific ocean, where they are particularly clear, and associated with a conjugate direction at 1500 km scale. A major finding is that the 2000 km scale geoid undulations dominate and had never been so clearly observed previously. This is due to the great precision of GRACE data at those wavelengths. Given the large scale of these undulations, they are most likely related to mantle processes. Taking into account observations and models from other geophysical information, as seismological tomography, convection and geochemical models and electrical conductivity in the mantle, we conceive that all these inputs indicate a directional fabric of the mantle flows at depth, reflecting how the history of subduction influences the organization of lower mantle upwellings. Numéro de notice : A2012-742 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2012.05455.x Date de publication en ligne : 19/04/2012 En ligne : https://doi.org/10.1111/j.1365-246X.2012.05455.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91491 [article]

Pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle / Cécilia Cadio in Earth and planetary science letters, vol 306 n° 1-2 (June 2011)  

Public [article]  inEarth and planetary science letters > vol 306 n° 1-2 (June 2011) . - pp 123 - 135 Titre : Pacific geoid anomalies revisited in light of thermochemical oscillating domes in the lower mantle Type de document : Article/Communication Auteurs : Cécilia Cadio, Auteur ; Isabelle Panet , Auteur ; Anne Davaille, Auteur ; Michel Diament , Auteur ; Laurent Métivier , Auteur ; Olivier de Viron, Auteur Année de publication : 2011 Article en page(s) : pp 123 - 135 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] convection [Termes IGN] données GRACE [Termes IGN] géoïde local [Termes IGN] levé gravimétrique [Termes IGN] manteau terrestre [Termes IGN] oscillation [Termes IGN] Pacifique (océan) [Termes IGN] Polynésie française [Termes IGN] volcan Résumé : (auteur) The geoid low over French Polynesia has been previously interpreted as the signature of an upper mantle upwelling associated with a low-viscosity zone located immediately below the lithosphere. We propose here an alternative explanation using new high-quality satellite gravity data and fluid mechanics constraints. We thus discuss the origin of the high concentration of hotspots in the Central Pacific, which is still debated. Satellite gravity data from the GRACE mission analyzed with wavelets allow us to better characterize the geoid low on French Polynesia and the large-scale positive geoid anomaly 600 km east of the Line Islands chain. We show that the geoid anomalies are consistent with thermochemical oscillating domes and we bring constraints on their density contrast and their upper limit depth under this hypothesis. The Central Pacific mantle would contain two thermochemical instabilities at different stages of their development: a rising dome (lighter) extending approximately from the CMB up to the transition zone beneath the South Pacific Superswell, toped by secondary plumes that generate short-lived hot spot chains, and a sinking dome (denser) in the lower mantle beneath the area located 600 km east of the Line Islands chain. Plate reconstructions further show that the latter could also have generated the Southern Line Islands 35 M.y. ago and Shatsky Rise 140 M.y. ago when it was in its ascending phase, while the South Pacific dome probably created Darwin Rise 100 M.y. ago in a same type of event. Numéro de notice : A2011-599 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.epsl.2011.03.040 Date de publication en ligne : 22/04/2011 En ligne : https://doi.org/10.1016/j.epsl.2011.03.040 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91645 [article]