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Auteur Isabelle Panet
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Wavelet modelling of the gravity field by domain decomposition methods: an example over Japan / Isabelle Panet in Geophysical journal international, vol 184 n° 1 (January 2011)
[article]
Titre : Wavelet modelling of the gravity field by domain decomposition methods: an example over Japan Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Yuki Kuroishi, Auteur ; Matthias Holschneider, Auteur Année de publication : 2011 Article en page(s) : pp 203 - 219 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] analyse harmonique
[Termes IGN] bruit blanc
[Termes IGN] bruit rose
[Termes IGN] harmonique sphérique
[Termes IGN] itération
[Termes IGN] Japon
[Termes IGN] modèle de géopotentiel local
[Termes IGN] potentiel de pesanteur terrestre
[Termes IGN] transformation en ondelettesRésumé : (auteur) With the advent of satellite gravity, large gravity data sets of unprecedented quality at low and medium resolution become available. For local, high resolution field modelling, they need to be combined with the surface gravity data. Such models are then used for various applications, from the study of the Earth interior to the determination of oceanic currents. Here we show how to realize such a combination in a flexible way using spherical wavelets and applying a domain decomposition approach. This iterative method, based on the Schwarz algorithms, allows to split a large problem into smaller ones, and avoids the calculation of the entire normal system, which may be huge if high resolution is sought over wide areas. A subdomain is defined as the harmonic space spanned by a subset of the wavelet family. Based on the localization properties of the wavelets in space and frequency, we define hierarchical subdomains of wavelets at different scales. On each scale, blocks of subdomains are defined by using a tailored spatial splitting of the area. The data weighting and regularization are iteratively adjusted for the subdomains, which allows to handle heterogeneity in the data quality or the gravity variations. Different levels of approximations of the subdomains normals are also introduced, corresponding to building local averages of the data at different resolution levels. We first provide the theoretical background on domain decomposition methods. Then, we validate the method with synthetic data, considering two kinds of noise: white noise and coloured noise. We then apply the method to data over Japan, where we combine a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoid is obtained at about 15 km resolution and a corrector grid for the surface model is derived. Numéro de notice : A2011-604 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2010.04840.x Date de publication en ligne : 01/01/2011 En ligne : https://doi.org/10.1111/j.1365-246X.2010.04840.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91678
in Geophysical journal international > vol 184 n° 1 (January 2011) . - pp 203 - 219[article]Documents numériques
en open access
Wavelet modelling of the gravity field .. - pdf éditeurAdobe Acrobat PDF Upper mantle rheology from GRACE and GPS postseismic deformation after the 2004 Sumatra‐Andaman earthquake / Isabelle Panet in Geochemistry, Geophysics, Geosystems, vol 11 n° 6 (June 2010)
[article]
Titre : Upper mantle rheology from GRACE and GPS postseismic deformation after the 2004 Sumatra‐Andaman earthquake Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Fred Pollitz, Auteur ; Valentin O. Mikhailov, Auteur ; Michel Diament , Auteur ; P. Banerjee, Auteur ; K. Grijalva, Auteur Année de publication : 2010 Article en page(s) : 20 p. Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Applications de géodésie spatiale
[Termes IGN] déformation de la croute terrestre
[Termes IGN] données GPS
[Termes IGN] données GRACE
[Termes IGN] manteau terrestre
[Termes IGN] rhéologie
[Termes IGN] séisme
[Termes IGN] SumatraRésumé : (auteur) Mantle rheology is one of the essential, yet least understood, material properties of our planet, controlling the dynamic processes inside the Earth's mantle and the Earth's response to various forces. With the advent of GRACE satellite gravity, measurements of mass displacements associated with many processes are now available. In the case of mass displacements related to postseismic deformation, these data may provide new constraints on the mantle rheology. We consider the postseismic deformation due to the Mw = 9.2 Sumatra 26 December 2004 and Mw = 8.7 Nias 28 March 2005 earthquakes. Applying wavelet analyses to enhance those local signals in the GRACE time varying geoids up to September 2007, we detect a clear postseismic gravity signal. We supplement these gravity variations with GPS measurements of postseismic crustal displacements to constrain postseismic relaxation processes throughout the upper mantle. The observed GPS displacements and gravity variations are well explained by a model of viscoelastic relaxation plus a small amount of afterslip at the downdip extension of the coseismically ruptured fault planes. Our model uses a 60 km thick elastic layer above a viscoelastic asthenosphere with Burgers body rheology. The mantle below depth 220 km has a Maxwell rheology. Assuming a low transient viscosity in the 60–220 km depth range, the GRACE data are best explained by a constant steady state viscosity throughout the ductile portion of the upper mantle (e.g., 60–660 km). This suggests that the localization of relatively low viscosity in the asthenosphere is chiefly in the transient viscosity rather than the steady state viscosity. We find a 8.1018 Pa s mantle viscosity in the 220–660 km depth range. This may indicate a transient response of the upper mantle to the high amount of stress released by the earthquakes. To fit the remaining misfit to the GRACE data, larger at the smaller spatial scales, cumulative afterslip of about 75 cm at depth should be added over the period spanned by the GRACE models. It produces only small crustal displacements. Our results confirm that satellite gravity data are an essential complement to ground geodetic and geophysical networks in order to understand the seismic cycle and the Earth's inner structure. Numéro de notice : A2010-655 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1029/2009GC002905 Date de publication en ligne : 19/06/2010 En ligne : https://doi.org/10.1029/2009GC002905 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=91728
in Geochemistry, Geophysics, Geosystems > vol 11 n° 6 (June 2010) . - 20 p.[article]Documents numériques
en open access
Upper mantle rheology from GRACE and GPS ... - pdf éditeurAdobe Acrobat PDF Wavelet modeling of the gravity field over Japan / Isabelle Panet in Bulletin of the Geographical survey institute, vol 57 (December 2009)
[article]
Titre : Wavelet modeling of the gravity field over Japan Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Yuki Kuroishi, Auteur ; Matthias Holschneider, Auteur Année de publication : 2009 Article en page(s) : pp 19 - 33 Note générale : Bibliographie
2e partie article : https://www.gsi.go.jp/common/000054750.pdfLangues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] bruit blanc
[Termes IGN] champ de pesanteur local
[Termes IGN] géoïde local
[Termes IGN] harmonique sphérique
[Termes IGN] Japon
[Termes IGN] levé gravimétrique
[Termes IGN] modèle de géopotentiel local
[Termes IGN] ondelette sphérique
[Termes IGN] transformation en ondelettesRésumé : (Auteur) Knowing the geoïd over Japan is essential for many geodetical and geophysical applications. Because of the tectonic settings of the area, significant geoid undulations occur in a wide range of spatial scales and make the determination of the geoïd a complex task. In some applications, high absolute accuracy at long and medium wavelengths is required for geoïd models with high resolution, which can be achieved by a proper combination of satellite gravity information with densely-distributed surface gravity data after careful consideration of their respective error characteristics. Here we show how to realize such a combination in a flexible way using spherical wavelets. The gravity potential is expressed as a linear combination of wavelets, whose coefficients are obtained by a least squares adjustment of the datasets. The combination needs to handle a large system of equations and we apply a domain decomposition method. First, we define sub-domains as subsets of wavelets. Based on the localization properties of the wavelets in space and frequency, we define hierarchical sub-domains of wavelets at different scales. On each scale, blocks of sub-domains are defined by using a tailored spatial splitting of the area. Second, we approximate the normal matrix for each block by introducing local approximation of the wavelets depending on the scale, in which local averages of the data are actually used for computation. Finally, we solve the system iteratively. In the beginning we validate the method with synthetic data, considering two kinds of noise: white noise and colored noise. We then apply the method to data over Japan: a satellite-based geopotential model, EIGEN-GL04S, and a local gravity model from a combination of land and marine gravity data and an altimetry-derived marine gravity model. A hybrid spherical harmonics/wavelet model of the geoïd is obtained at about 15 km resolution and the residuals indicate the existence of possible biases in the surface model. This information is used to correct the local model and the method is repeated with the corrected data, resulting in an improved hybrid model of the gravity field over Japan. Copyright Geographical Survey Institute Numéro de notice : A2009-558 Affiliation des auteurs : non IGN Thématique : POSITIONNEMENT Nature : Article DOI : sans En ligne : https://www.gsi.go.jp/common/000054749.pdf Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=30187
in Bulletin of the Geographical survey institute > vol 57 (December 2009) . - pp 19 - 33[article]Réservation
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Code-barres Cote Support Localisation Section Disponibilité 250-09011 RAB Revue Centre de documentation En réserve L003 Disponible Local multi-polar expansions in potential field modeling / B. Minchev in Earth, Planets and Space, vol 61 n° 10 (October 2009)
[article]
Titre : Local multi-polar expansions in potential field modeling Type de document : Article/Communication Auteurs : B. Minchev, Auteur ; Aude Chambodut, Auteur ; Matthias Holschneider, Auteur ; Isabelle Panet , Auteur ; Eckehard Schöll, Auteur ; Mioara Mandea, Auteur ; Guillaume Ramillien, Auteur Année de publication : 2009 Projets : 1-Pas de projet / Article en page(s) : pp 1127 - 1141 Note générale : bibliographie
This work was supported by the Deutsche Forschungsgemeinschaft(DFG) within the framework of the projects BMBF/DFG “GEOTECHNOLOGIEN” and the DFG project KO 2870/3-1.Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] données CHAMP
[Termes IGN] données géophysiques
[Termes IGN] harmonique sphérique
[Termes IGN] problème inverseRésumé : (auteur) The satellite era brings new challenges in the development and the implementation of potential field models. Major aspects are, therefore, the exploitation of existing space- and ground-based gravity and magnetic data for the long-term. Moreover, a continuous and near real-time global monitoring of the Earth system, allows for a consistent integration and assimilation of these data into complex models of the Earth’s gravity and magnetic fields, which have to consider the constantly increasing amount of available data. In this paper we propose how to speed up the computation of the normal equation in potential filed modeling by using local multi-polar approximations of the modeling functions. The basic idea is to take advantage of the rather smooth behavior of the internal fields at the satellite altitude and to replace the full available gravity or magnetic data by a collection of local moments. We also investigate what are the optimal values for the free parameters of our method. Results from numerical experiments with spherical harmonic models based on both scalar gravity potential and magnetic vector data are presented and discussed. The new developed method clearly shows that very large datasets can be used in potential field modeling in a fast and more economic manner. Numéro de notice : A2009-605 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1186/BF03352965 Date de publication en ligne : 30/11/2009 En ligne : https://doi.org/10.1186/BF03352965 Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=95757
in Earth, Planets and Space > vol 61 n° 10 (October 2009) . - pp 1127 - 1141[article]Retrieving earthquake signature in GRACE gravity solutions / Olivier de Viron in Geophysical journal international, vol 174 n° 1 (July 2008)
[article]
Titre : Retrieving earthquake signature in GRACE gravity solutions Type de document : Article/Communication Auteurs : Olivier de Viron, Auteur ; Isabelle Panet , Auteur ; Valentin O. Mikhailov, Auteur ; Michel Van Camp, Auteur ; Michel Diament , Auteur Année de publication : 2008 Article en page(s) : pp 14 - 20 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie physique
[Termes IGN] champ de pesanteur terrestre
[Termes IGN] décomposition en fonctions orthogonales empiriques
[Termes IGN] déformation de la croute terrestre
[Termes IGN] données GRACE
[Termes IGN] géoïde terrestre
[Termes IGN] séisme
[Termes IGN] série temporelle
[Termes IGN] variation temporelleRésumé : (auteur) The GRACE satellites have been orbiting the Earth since 2002, monitoring the time variable gravity field. Some of the observed fluctuations are due to geodynamic causes, but they are often hidden in the complex signal, composed of hydrology, ocean, atmosphere, and geodynamics, the signal of geodynamic origin being usually the smallest. In addition, dealiasing residuals and noise make the separation of the signal from the different causes more difficult. We proposed a method based on the Empirical Orthogonal Function decomposition to extract the signal of physical origin, under the hypothesis that the physical signal is spatially more consistent than the noise and aliasing incomplete correction. We used synthetic geoid variations associated with earthquakes located at nearly 2000 positions at the Earth surface, based on several examples of large actual subduction events. We show that, with the present day accuracy, we can retrieve the geoid variations associated with more than 98 per cent of the earthquakes of magnitude 9 or above, around 60 per cent for magnitude 8.8, 40 per cent for magnitude 8.6 and 33 per cent for magnitude 8.3. Some events, with the right properties and location, can be detected with magnitude as low as 8. We then applied the method to the GRACE solutions, and retrieved the Hokkaido event (2003) and the Sumatra event (2004), which is in agreement with the retrieval rates mentioned here above. Numéro de notice : A2008-632 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2008.03807.x En ligne : https://doi.org/10.1111/j.1365-246X.2008.03807.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=103439
in Geophysical journal international > vol 174 n° 1 (July 2008) . - pp 14 - 20[article]Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity / Isabelle Panet in Geophysical journal international, vol 171 n° 1 (Octobre 2007)PermalinkNew insights on intraplate volcanism in French Polynesia from wavelet analysis of GRACE, CHAMP, and sea surface data / Isabelle Panet in Journal of geophysical research : Solid Earth, vol 111 n° B9 (September 2006)PermalinkExtracting low frequency climate signal from GRACE data / Olivier de Viron in eEarth, vol 1 n° 1 (2006)PermalinkReprésentation du champ de pesanteur sur des repères d'ondelettes sphériques / Isabelle Panet in Bulletin d'information scientifique et technique de l'IGN, n° 75 (mars 2006)PermalinkWavelet frames:An alternative to spherical harmonic representation of potential fields / Aude Chambodut in Geophysical journal international, vol 163 n° 3 (December 2005)PermalinkPermalinkPermalinkCan tectonic processes be recovered from new gravity satellite data? / Valentin O. Mikhailov in Earth and planetary science letters, vol 228 n° 3-4 (15 December 2004)PermalinkComparaison de trois familles d'ondelettes pour la représentation du champ de pesanteur terrestre / Isabelle Panet (2003)PermalinkLe SIG, outil de l'aménagement urbain, [Colloque organisé par les élèves IG de la promotion 2000], le jeudi 3 mai 2001 à l'ENSG / Jean-Christophe Barreteau (2001)Permalink
Head of the Gravity Field research team