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Dense mantle flows periodically spaced below ocean basins / Isabelle Panet in Earth and planetary science letters, vol 594 (15 September 2022)  

Public [article]  inEarth and planetary science letters > vol 594 (15 September 2022) . - n° 117745 Titre : Dense mantle flows periodically spaced below ocean basins Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Marianne Greff-Lefftz, Auteur ; Barbara Romanowicz, Auteur Année de publication : 2022 Projets : Université de Paris / Clerici, Christine Article en page(s) : n° 117745 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] champ de pesanteur terrestre [Termes IGN] convection [Termes IGN] déformation de la croute terrestre [Termes IGN] dynamique des fluides [Termes IGN] fond marin [Termes IGN] Indien (océan) [Termes IGN] lithosphère [Termes IGN] manteau terrestre [Termes IGN] Pacifique (océan) Résumé : (auteur) Understanding mantle flow is key to elucidate how deep Earth dynamics relate to tectonics at the global scale. The convective mass transport is reflected in lateral variations of the gravity field, seismic velocities, as well as deformations of the Earth's surface. Yet, upper to mid-mantle dynamics have been difficult to constrain at the medium scales of thousands of km. Here, we analyze the second-order horizontal derivatives of seafloor topography and of the gravity potential over the Pacific and Northern Indian ocean basins, and provide evidence for periodic undulations of 1600-2000 km wavelength in both signals, elongated along the direction of absolute plate motion. We investigate potential crustal and lithospheric sources and show that at least part of this signal must originate below the lithosphere, with alignments of sub-lithospheric upper mantle mass excess below seafloor lows. Furthermore, we find that these alignments coincide geographically over wide areas with similarly periodic slow seismic velocity fingers located at upper mantle depths. These two fields may thus record an intermediate scale of mantle convection below ocean basins, which cannot be explained by purely thermal convection and requires instead lateral variations in composition in the upper mantle. Elucidating the nature of the detected mass excess sources coincident with the slow seismic velocities calls for a joint dynamical modeling of all observations in a thermo-chemical context. Numéro de notice : A2022-692 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1016/j.epsl.2022.117745 En ligne : https://doi.org/10.1016/j.epsl.2022.117745 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=101809 [article]

Metamorphic transformation rate over large spatial and temporal scales constrained by geophysical data and coupled modelling / Gyorgy Hetényl in Journal of metamorphic geology, vol 39 n° 9 (December 2021)  

Public [article]  inJournal of metamorphic geology > vol 39 n° 9 (December 2021) . - pp 1131 - 1143 Titre : Metamorphic transformation rate over large spatial and temporal scales constrained by geophysical data and coupled modelling Type de document : Article/Communication Auteurs : Gyorgy Hetényl, Auteur ; Kristel Chanard , Auteur ; Lukas P. Baumgartner, Auteur ; Frédéric Herman, Auteur Année de publication : 2021 Projets : 3-projet - voir note / Clerici, Christine Article en page(s) : pp 1131 - 1143 Note générale : bibliographie We are grateful to the Swiss National Science Foundation for funding project OROG3NY through grant PP00P2_157627. Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] croute terrestre [Termes IGN] géodynamique [Termes IGN] Inde [Termes IGN] modèle numérique [Termes IGN] roche métamorphique Résumé : (auteur) Metamorphic transformation rates are classically determined on decimetre-scale field samples and from laboratory experiments at smaller scales. Here we present a geophysical approach based on field data and joint geophysical–petrological modelling to quantify the average rate of metamorphic transformations at the 10–100-kilometre and million-year scales. The model simulates the eclogitization of Indian lower crust as it penetrates beneath southern Tibet. Metamorphic transformation of the lower crust is tracked by its densification, the effect of which is then compared to observed gravity anomalies. From the modelling we find that the Indian lower crust's overall densification requires a partially hydrated initial composition. Moreover, the modelled evolution of this densification compared to what is predicted by pressure–temperature–density grids is consistent with delayed, far-from-equilibrium metamorphism. The Indian lower crust descends underneath the Himalaya until beneath southern Tibet in a thermodynamically metastable state until the first dehydration reactions are reached. This observation is used to determine the average rate of metastable rock transformation to an eclogite facies assemblage, constrained at between ~6 × 10−9 and 5 × 10−7 g/cm2/year, and reaction affinity at 0.8–1.6 kJ/mol oxygen. Compared to field and laboratory data, this range of results matches the effective rates typically associated with regional metamorphism. This fit and correlation across the scales legitimates the use of transformation rates determined at small scales in large-scale geodynamic studies. Numéro de notice : A2021-789 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/jmg.12604 En ligne : https://doi.org/10.1111/jmg.12604 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=98988 [article]

What is the impact of tectonic plate movement on country size? A long-term forecast / Kamil Maciuk in Remote sensing, vol 13 n° 23 (December-1 2021)  

Public [article]  inRemote sensing > vol 13 n° 23 (December-1 2021) . - n° 4872 Titre : What is the impact of tectonic plate movement on country size? A long-term forecast Type de document : Article/Communication Auteurs : Kamil Maciuk, Auteur ; Michal Apollo, Auteur ; Anita Kukulska-Kozieł, Auteur ; et al., Auteur Année de publication : 2021 Article en page(s) : n° 4872 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] déformation de la croute terrestre [Termes IGN] frontière [Termes IGN] lithosphère [Termes IGN] modèle de simulation [Termes IGN] montée du niveau de la mer [Termes IGN] pays [Termes IGN] superficie [Termes IGN] tectonique des plaques [Termes IGN] World Geodetic System 1984 Résumé : (auteur) The Earth’s surface is under permanent alteration with the area of some nations growing or shrinking due to natural or man-made processes, for example sea level change. Here, based on the NUVEL 1A model, we forecast (in 10, 25, and 50 years) the changes in area for countries that are located on the border of the major tectonic plates. In the analysis we identify countries that are projected to gain or lose land due to the tectonic plate movement only. Over the next 50 years, the global balance of area gains (0.4 km2) and losses (12.7 km2) is negative. Thus, due to the movements of lithospheric plates, the land surface of the Earth will decrease by 12 km2 in 50 years. Overall, the changes are not that spectacular, as in the case of changes in sea/water levels, but in some smaller countries, projected losses exceed a few thousand square metres a year, e.g., in Nepal the losses exceed 10,000 m2 year−1. Methodologically, this paper finds itself between metric analysis and essay, trying to provoke useful academic discussion and incite educators’ interests to illustrate to students the tectonic movement and its force. Limitations of the used model have been discussed in the methodology section. Numéro de notice : A2021-877 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : 10.3390/rs13234872 Date de publication en ligne : 30/11/2021 En ligne : https://doi.org/10.3390/rs13234872 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99144 [article]

Height system unification and estimation of the lithospheric structure beneath Vietnam through high-resolution gravity field and quasigeoid modeling / Dinh Toan Vu (2021)  

Public Titre : Height system unification and estimation of the lithospheric structure beneath Vietnam through high-resolution gravity field and quasigeoid modeling Titre original : Unification du système de hauteur et estimation de la structure lithosphérique sous le Vietnam utilisant la modélisation du champ de gravité et du quasigéoïde à haute résolution Type de document : Thèse/HDR Auteurs : Dinh Toan Vu, Auteur ; Sylvain Bonvalot, Directeur de thèse ; Sean L. Bruinsma, Directeur de thèse Editeur : Toulouse : Université de Toulouse Année de publication : 2021 Importance : 234 p. Format : 21 x 30 cm Note générale : bibliographie Thèse en vue de l'obtention du Doctorat de l'Université de Toulouse délivrée par l'Université Toulouse 3 - Paul Sabatier Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] champ de pesanteur terrestre [Termes IGN] données GNSS [Termes IGN] données GOCE [Termes IGN] géoïde gravimétrique [Termes IGN] géoïde local [Termes IGN] lithosphère [Termes IGN] modèle de géopotentiel local [Termes IGN] nivellement [Termes IGN] quasi-géoïde [Termes IGN] Viet Nam Index. décimale : THESE Thèses et HDR Résumé : (auteur) The goal of this work was twofold. The first part was devoted to the research of the size and physical shape of the Earth in Vietnam through the determination of a local gravimetric quasigeoid model. The second part was to better constrain the Earth's interior structure beneath Vietnam by determining the Moho and Lithosphere-Asthenosphere Boundary (LAB) depth models. For the first objective, a high-resolution gravimetric quasigeoid model for Vietnam and its surrounding areas was determined based on new land gravity data in combination with fill-in data where no gravity data existed. The resulting quasigeoid model was evaluated using 812 GNSS/levelling points in the study region. This comparison indicates that the quasigeoid model has a standard deviation of 9.7 cm and 50 cm in mean bias. This new local quasigeoid model for Vietnam represents a significant improvement over the global models EIGEN-6C4 and EGM2008, which have standard deviations of 19.2 and 29.1 cm, respectively, when compared to the GNSS/levelling data. An essential societal and engineering application of the gravimetric quasigeoid is in GNSS levelling, and a vertical offset model for Vietnam and its surrounding areas was determined based on the GNSS/levelling points and gravimetric-only quasigeoid model for this purpose. The offset model was evaluated using cross-validation technique by comparing with GNSS/levelling data. Results indicate that the offset model has a standard deviation of 5.9 cm in the absolute sense. Thanks to this offset model, GNSS levelling can be carried out over most of Vietnam's territory complying to third-order levelling requirements, while the accuracy requirements for fourth-order levelling networks is met for the entire country. To unify the height system towards the International Height Reference Frame (IHRF), the zero-height geopotential value for the Vietnam Local Vertical Datum W_0^LVD was determined based on two approaches: 1) Using high-quality GNSS/levelling data and the estimated gravimetric quasigeoid model, 2) Using the Geodetic Boundary Value Problem (GBVP) approach based on the GOCE global gravity field model enhanced with terrestrial gravity data. This geopotential value can be used to connect the height system of Vietnam with the neighboring countries. Moreover, the GBVP approach was also used for direct determination of the gravity potential on the surface at three GNSS Continuously Operating Reference Station (CORS) stations at epoch 2018.0 in Vietnam. Based on time series of the vertical component derived from these GNSS observations as well as InSAR data, temporal variations in the geopotential were also estimated on these permanent GNSS stations. This enables monitoring of the vertical datum and detect possible deformation. These stations may thus contribute to increase the density of reference points in the IHRF for this region. For the second objective, the local quasigeoid model was first converted to the geoid. Then, high-resolution Moho and LAB depth models were determined beneath Vietnam based on the local isostatic hypothesis using the geoid height derived from the estimated geoid, elevation data and thermal analysis. From new land gravity data, a complete grid and map of gravity anomalies i.e., Free-air, Bouguer and Isostatic was determined for the whole of Vietnam. The Moho depth was also computed based on the gravity inversion using the Bouguer gravity anomaly grid. All new models are computed at 1' resolution. The resulting Moho and LAB depth models were evaluated using available seismic data as well as global and local lithospheric models available in the study region. [...] Note de contenu : 1- Introduction 2- Theoretical basis 3- Data and map of gravity anomalies 4- The gravimetric quasigeoid solution 5- Quasigeoïd application for GNSS levelling and height system unification 6- Quasigeoid application for determination of the lithospheric structure 7- Conclusion and perspectives Numéro de notice : 28495 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Thèse française Note de thèse : Thèse de Doctorat : Sciences de la Terre et des Planètes Solides : Toulouse : 2021 Organisme de stage : Geosciences Environnement Toulouse GET DOI : sans En ligne : http://www.theses.fr/2021TOU30050 Format de la ressource électronique : URL Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=99240

From space to lithosphere: inversion of the GOCE gravity gradients. Supply to the Earth’s interior study / Matthieu Plasman in Geophysical journal international, vol 223 n° 1 (October 2020)  

Public [article]  inGeophysical journal international > vol 223 n° 1 (October 2020) . - pp 398 - 419 Titre : From space to lithosphere: inversion of the GOCE gravity gradients. Supply to the Earth’s interior study Type de document : Article/Communication Auteurs : Matthieu Plasman, Auteur ; Christel Tiberi, Auteur ; Cécilia Cadio, Auteur ; Anita Thea Saraswati, Auteur ; Gwendoline Pajot-Métivier , Auteur ; Michel Diament , Auteur Année de publication : 2020 Projets : 3-projet - voir note / Clerici, Christine Article en page(s) : pp 398 - 419 Note générale : bibliographie TOSCA project financing (PIGGS project) Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique [Termes IGN] anomalie de pesanteur [Termes IGN] données GOCE [Termes IGN] géophysique interne [Termes IGN] gradient de gravitation [Termes IGN] gravimétrie spatiale [Termes IGN] lithosphère [Termes IGN] problème inverse Résumé : (auteur) The emergence of high resolution satellite measurements of the gravitational field (GOCE mission) offers promising perspectives for the study of the Earth’s interior. These new data call for the development of innovant analysis and interpretation methods. Here we combine a forward prism computation with a Bayesian resolution approach to invert for these gravity gradient data configuration. We apply and test our new method on satellite data configuration, that is 225 km height with a global and homogeneous geographic distribution. We first quantify the resolution of our method according to both data and parametrization characteristics. It appears that for reasonable density contrast values (0.1 g cm−3) crustal structures have to be wider than ∼28 km to be detectable in the GOCE signal. Deeper bodies are distinguishable for greater size (35 km size at 50 km depth, ∼80 km at 300 km depth). We invert the six tensor components, among which five are independent. By carefully testing each of them and their different combinations, we enlighten a trade off between the recovery of data and the sensitivity to inversion parameters. We particularly discussed this characteristic in terms of geometry of the synthetic model tested (structures orientation, 3-D geometry, etc.). In terms of RMS value, each component is always better explained if inverted solely, but the result is strongly affected by the inversion parametrization (smoothing, variances, etc.). On the contrary, the simultaneous inversion of several components displays a significant improvement for the global tensor recovery, more dependent on data than on density variance or on smoothness control. Comparing gravity and gradient inversions, we highlight the superiority of the GG data to better reproduce the structures especially in terms of vertical location. We successfully test our method on a realistic case of a complex subduction case for both gradient and gravity data. While the imaging of small crustal structures requires terrestrial gravity data set, the longest wavelength of the slab is well recovered with both data sets. The precision and homogeneous coverage of GOCE data however, counterbalance the heterogeneous and often quite non-existence coverage of terrestrial gravity data. This is particularly true in large areas which requires a coherent assemblage of heterogeneous data sets, or in high relief, vegetally covered and offshore zones. Numéro de notice : A2020-823 Affiliation des auteurs : UMR IPGP-Géod+Ext (2020- ) Autre URL associée : vers HAL Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1093/gji/ggaa318 Date de publication en ligne : 26/06/2020 En ligne : https://doi.org/10.1093/gji/ggaa318 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=97260 [article]

Automated estimation and tools to extract positions, velocities, breaks, and seasonal terms from daily GNSS measurements: illuminating nonlinear Salton Trough deformation / Michael B. Heflin in Earth and space science, vol 7 n° 7 (July 2020)  

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ITRF2014, Earth figure changes, and geocenter velocity: Implications for GIA and recent ice melting / Laurent Métivier in Journal of geophysical research : Solid Earth, vol 125 n° 2 (February 2020)  

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A generalized theory of the figure of the Earth : formulae / Chengli Huang in Journal of geodesy, vol 93 n° 3 (March 2019)  

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A generalized theory of the figure of the Earth : on the global dynamical flattening / Chenjun Liu in Journal of geodesy, vol 93 n° 3 (March 2019)  

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Reconciling upper mantle seismic velocity and density structure below ocean basins / Isabelle Panet (2019)

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Contribution actuelle de la calotte Antarctique à la variation du niveau marin / Clémence Chupin (2018) 

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Inverting Glacial Isostatic Adjustment signal using Bayesian framework and two linearly relaxing rheologies / Lambert Caron in Geophysical journal international, vol 209 n° 2 (May 2017)  

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Gravity forward modeling with a tesseroid-based rock-water-ice approach / Thomas Grombein (2017)  

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Evidence for postglacial signatures in gravity gradients: A clue in lower mantle viscosity / Laurent Métivier in Earth and planetary science letters, vol 452 (October 2016)  

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Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism / Grace E. Shephard in Geophysical research letters, vol 43 n° 8 (28 April 2016)    

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