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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
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Upper mantle rheology from GRACE and GPS ... - pdf éditeurAdobe Acrobat PDF 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)
[article]
Titre : Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity Type de document : Article/Communication Auteurs : Isabelle Panet , Auteur ; Valentin O. Mikhailov, Auteur ; Michel Diament , Auteur ; Fred Pollitz, Auteur ; Geoffrey King, Auteur ; Olivier de Viron, Auteur ; Matthias Holschneider, Auteur ; Richard Biancale, Auteur ; Jean-Michel Lemoine, Auteur Année de publication : 2007 Article en page(s) : pp 177 - 190 Note générale : bibliographie Langues : Anglais (eng) Descripteur : [Vedettes matières IGN] Géodésie spatiale
[Termes IGN] données GRACE
[Termes IGN] géoïde local
[Termes IGN] ondelette
[Termes IGN] séisme
[Termes IGN] subductionRésumé : (auteur) The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December (Mw = 9.2) and 2005 March (Mw = 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin. Numéro de notice : A2007-673 Affiliation des auteurs : LAREG+Ext (1991-2011) Thématique : POSITIONNEMENT Nature : Article nature-HAL : ArtAvecCL-RevueIntern DOI : 10.1111/j.1365-246X.2007.03525.x Date de publication en ligne : 01/10/2007 En ligne : https://doi.org/10.1111/j.1365-246X.2007.03525.x Format de la ressource électronique : URL article Permalink : https://documentation.ensg.eu/index.php?lvl=notice_display&id=102773
in Geophysical journal international > vol 171 n° 1 (Octobre 2007) . - pp 177 - 190[article]