74 research outputs found
"A Margarita Debayle", Sin Datar
No full textabstract: Handwritten poem composed by Rubén Darío.The original Rubén Darío Papers 1882-1945 (MSS-339) are located at ASU Libraries Archives & Special Collections. For more information about visiting the collection see http://hdl.handle.net/2286/L.A.0.The first page has the title "A Margarita Debayle" and Ruben Dario's name. Likewise the odd numbers have written the title as well as Ruben Dario's name.Margarita Debayle (July 4, 1900 - December 19, 1983) was Luis H. Debayle's daughter, a friend of Rubén Darío.All pages are numerated in roman numerals
Recibo de Rubén Darío para L. H. Debayle, 1908 Octubre 10
No full textabstract: The receipt is an acknowledgment for an amount of 2,000 Pesetas to Luis H. Debayle. At the time of this receipt, Debayle was the Mexican Consul in France. Rubén Darío was in Madrid when this receipt was written.The original Rubén Darío Papers 1882-1945 (MSS-339) are located at ASU Libraries Archives & Special Collections. For more information about visiting the collection see http://hdl.handle.net/2286/L.A.0.Luis H. Debayle (1865 - 1938) was a recognized and prestigious Nicaraguan doctor. He had a close friendship with Rubén Darío
3-D Mapping of the Seismic Attenuation in the Upper Mantle
No full textL'objectif de cette thèse est de construire un modèle d'atténuation sismique du manteau supérieur dela Terre en utilisant un jeu de données original construit par Debayle et Ricard (2012). Ce jeu dedonnées est l'un des plus complet au monde (plus de 375 000 sismogrammes analysés pour extrairel'atténuation et la vitesse de phase du mode fondamental et des cinq premiers harmoniques des ondesde Rayleigh).Les mesures d'atténuation sont tout d'abord traitées pour extraire les effets de l'expansion géométriqueet de la focalisation, minimiser les effets d'erreurs sur la source, écarter les mesures incertaines etregrouper les mesures redondantes. Elles sont ensuite régionalisées pour obtenir des cartes desvariations latérales de l'atténuation des ondes de Rayleigh pour chaque mode et chaque période. Ladernière étape est l'inversion en profondeur des cartes. Elle permet d'obtenir QsADR17, un modèle 3Dde l'atténuation des ondes S dans le manteau supérieur.QsADR17 est corrélé avec la tectonique de surface jusqu'à 200 km de profondeur, avec une faibleatténuation sous les continents et une forte atténuation sous les océans. Des anomalies de forteatténuation sont observées jusqu'à 150~km de profondeur sous les rides océaniques, et persistent à plusgrande profondeur jusque dans la zone de transition sous la plupart des points chauds. La présence delarges anomalies atténuantes situées à 150 km de profondeur sous l'océan Pacifique suggère queplusieurs panaches thermiques viennent s'étaler dans l'asthénosphère. Nous avons également détecté laprésence d'hétérogénéités de composition à la base des cratons et dans un certain nombre de régionsactives.The aim of this study is to build a 3-D attenuation model of Earth's upper-mantle using a unique datasetbuilt by Debayle & Ricard (2012). This dataset is among the largest in the world: more than 375,000seismograms were analyzed to extract Rayleigh-wave attenuation and velocity measurements for thefondamental mode and the five first harmonics between 40 and 240 s periods.First, attenuation measurements are processed to extract the effects of geometrical attenuation and offocusing and defocusing, in order to minimize the influence of errors on the seismic source, to avoidpotentially incorrect data, and to cluster redondant measurements. Then, measurements are regionalizedto obtain Rayleigh-wave maps for each mode and each period. The last step is the inversion of thesemaps to obtain the depth dependent attenuation. Eventually, we obtain QsADR17, a 3-D model of Swaveattenuation in the upper mantle.QsADR17 is correlated with surface tectonics down to 200 km depth, with low attenuation under thecontinents and high attenuation under the oceans. High-attenuation anomalies are found under oceanicridges down to 150~km depth, and under most of the hotspots at larger depth down to the transitionzone. A large high-attenuation anomaly at 150~km depth under the Pacific ocean suggest that thermalplumes pound into the asthenosphere. We also detect compositional heterogeneities at the base of thecratons and in active areas
A global shear velocity model of the upper mantle from fundamental and higher Rayleigh mode measurements
No full textInternational audienceWe present DR2012, a global SV-wave tomographic model of the upper mantle. We use an extension of the automated waveform inversion approach of Debayle (1999) which improves our mapping of the transition zone with extraction of fundamental and higher-mode information. The new approach is fully automated and has been successfully used to match approximately 375,000 Rayleigh waveforms. For each seismogram, we obtain a path average shear velocity and quality factor model, and a set of fundamental and higher-mode dispersion and attenuation curves. We incorporate the resulting set of path average shear velocity models into a tomographic inversion. In the uppermost 200 km of the mantle, SV wave heterogeneities correlate with surface tectonics. The high velocity signature of cratons is slightly shallower (approximate to 200 km) than in other seismic models. Thicker continental roots are not required by our data, but can be produced by imposing a priori a smoother model in the vertical direction. Regions deeper than 200 km show no velocity contrasts larger than +/- 1\% at large scale, except for high velocity slabs within the transition zone. Comparisons with other seismic models show that current surface wave datasets allow to build consistent models up to degrees 40 in the upper 200 km of the mantle. The agreement is poorer in the transition zone and confined to low harmonic degrees (<= 10)
Rayleigh wave phase velocity and error maps up to the fifth overtone
No full textInternational audienceWe present a global data set of phase velocity maps for Rayleigh waves, with their errors. These maps are obtained from the tomographic inversion of phase velocity curves measured in the period range 40–250 s by Debayle and Ricard (2012), completed with new measurements at longer periods, between 150 and 360 s. The full data set includes ∼22,000,000 phase velocity measurements combined to build 60 phase velocity maps covering the period range 40–360 s for the fundamental mode and up to the fifth overtone. Each phase velocity map is provided with its a posteriori error, resulting in a unique data set which can be combined with other seismic measurements (surface waves, normal modes, and body waves) in regional and global tomographic studies. A preliminary inversion of this data set shows that it provides constraints on the shear velocity structure down to 1000 km depth
Seismic observations of large-scale deformation at the bottom of fast-moving plates
No full textcited By 65International audienceWe present a new tomographic model of azimuthal anisotropy in the upper mantle, DR2012, and discuss in details the geodynamical causes of this anisotropy. Our model improves upon DKP2005 seismic model (Debayle et al., 2005) through a larger dataset (expanded by a factor ~3.7) and a new approach which allows us to better extract fundamental and higher-mode information. Our results confirm that on average, azimuthal anisotropy is only significant in the uppermost 200-250 km of the upper mantle where it decreases regularly with depth. We do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates, slow oceanic plates or continents. The anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity; it peaks in the asthenosphere around 150 km depth, it is very weak for plate velocities smaller than 3cmyr -1, increases significantly between 3 and 5cmyr -1, and saturates for plate velocities larger than 5cmyr -1. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath the fastest-moving plates (India, Coco, Nazca, Australia, Philippine Sea and Pacific plates). Beneath slower plates, plate-motion parallel anisotropy is only observed locally, which suggests that the mantle flow below these plates is not controlled by the lithospheric motion (a minimum plate velocity of around 4cmyr -1 is necessary for a plate to organize the flow in its underlying asthenosphere). The correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak. A better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age. The transition between frozen-in and active anisotropy occurs across the typical age isotherm that defines the bottom of the thermal lithosphere around 1100°C. Under fast continents (mostly under Australia and India), the present-day velocity orients also the anisotropy in a depth range around 150-200 km depth which is not deeper than what is observed under oceans. © 2013 Elsevier B.V
Study of the Earth's crust and upper mantle deformation from seismic anisotropy in tomographic models
No full textL’anisotropie est souvent utilisée en sismologie comme proxy de la déformation des roches. Elle se développe lorsque des minéraux acquièrent une orientation préférentielle. C’est le cas de l’olivine des péridotites du manteau qui s’aligne selon la direction des flux de matière. Néanmoins, l’anisotropie observée en tomographie peut aussi provenir d’hétérogénéités chimiques non résolues par les ondes sismiques longues périodes : elle s’apparente alors à̀ de l’anisotropie artificielle. Les théories et développements méthodologiques actuels ne permettent pas de distinguer l’anisotropie réelle de l’anisotropie artificielle dans les signaux sismiques. Dans cette thèse nous avons utilisé des modèles simples de manteau terrestre pour étudier théoriquement et numériquement le lien entre le niveau d’hétérogénéités non résolues et l’anisotropie radiale artificielle. Nous en avons conclu que l’anisotropie est proportionnelle au carré des hétérogénéités et que 10% de contraste de vitesse sismique peut engendrer plus de 3% d’anisotropie, un niveau non négligeable au regard des observations tomographiques. Une tomographie 3-D anisotrope de l’Europe, centrée sur les Alpes et les Apennins, a également enté réalisée. Les données d’ondes de surface utilisées sont issues de corrélations de bruit sismique et permettent d’imager la croûte et le manteau supérieur. La structure isotrope de notre modelé illumine particulièrement bien la plaque adriatique en subduction sous les Apennins ainsi qu’une rupture de ce panneau située au sud de la chaîne. Par ailleurs, la méthode d’inversion en profondeur utilisée prend en compte le biais entre anisotropie et hétérogénéités. Nous présentons ainsi le premier modelé 3-D d’anisotropie radiale en Europe réalisé pour des profondeurs aussi faibles. Nos résultats suggèrent que la croûte inférieure est marquée par une structuration horizontale dans les Apennins, probablement en lien avec la déformation extensive actuelle observée dans la région.Seismic anisotropy is often used as a proxy for rock deformation. It arises from the preferred orientation of anisotropic minerals. For instance, olivine in mantellic peridotites align according to mantle flow. However, anisotropy in tomographic models can be the result of small scale heterogeneities unresolved by long period seismic waves. It is thus considered as artificial. Theories and methodological developments do not allow to distinguish the relative contributions of real and artificial anisotropy in seismic signals. In this thesis, we used simple models of the Earth’s mantle to analytically and numerically study the link between unresolved heterogeneities and the level of artificial radial anisotropy. We concluded that anisotropy is proportional to the square of heterogeneities and that 10% of velocity contrast can be responsible for 3% of anisotropy, which is non negligible compared to the observed anisotropy in tomography. A 3-D anisotropic model of Europe, focusing on the Alps and Apennines, was constructed from surface waves data. The dispersion measurements were made from noise correlation and allow to image the crust and uppermost mantle. The isotropic structure of the model shows particularly well the Adriatic plate subducting under the Apennines, as well as a slab break-off in the Southern part of the chain. The method used for the depth inversion takes into account the trade-off between layering and anisotropy. Our model is therefore the first 3-D model of radial anisotropy built at shallow depths in Europe. Our results suggest that the lower crust has a horizontal organization in the Apennines, probably related to the extensive regime observed in the area
Global multiple-frequency S-wave tomography of the Earth’s mantle
No full textAfin de mieux contraindre la structure interne de la Terre, de nouveaux développements théoriques, sur la propagation des ondes, ont émergé ces dernières années. Une de ces nouvelles méthodes est la tomographie multi-fréquences, qui vise à exploiter la dépendance en fréquence des temps de parcours des ondes de volume, liée aux effets de diffraction. En utilisant cette méthode, cette thèse a pour objectif d'obtenir un modèle tomographique 3-D du manteau en ondes de cisaillement à ``haute-résolution'', qui puisse contribuer à améliorer nos connaissances sur la dynamique de la Terre.For better constraining the structure of the Earth's interior, new theoretical developments on seismic wave propagation have emerged in recent years, and received increasing attention in tomography. One of these new methods is the multiple-frequency tomography, which aims at exploiting the frequency-dependency of body wave travel times related to diffraction effects. In this thesis, we have applied this method in order to obtain a ``high-resolution'' 3-D shear-wave tomographic model of the mantle, that could contribute to a better understanding of the Earth's dynamics
Seismic observations of large-scale deformation at the bottom of fast-moving plates
No full textcited By 65International audienceWe present a new tomographic model of azimuthal anisotropy in the upper mantle, DR2012, and discuss in details the geodynamical causes of this anisotropy. Our model improves upon DKP2005 seismic model (Debayle et al., 2005) through a larger dataset (expanded by a factor ~3.7) and a new approach which allows us to better extract fundamental and higher-mode information. Our results confirm that on average, azimuthal anisotropy is only significant in the uppermost 200-250 km of the upper mantle where it decreases regularly with depth. We do not see a significant difference in the amplitude of anisotropy beneath fast oceanic plates, slow oceanic plates or continents. The anisotropy projected onto the direction of present plate motion shows a very specific relation with the plate velocity; it peaks in the asthenosphere around 150 km depth, it is very weak for plate velocities smaller than 3cmyr -1, increases significantly between 3 and 5cmyr -1, and saturates for plate velocities larger than 5cmyr -1. Plate-scale present-day deformation is remarkably well and uniformly recorded beneath the fastest-moving plates (India, Coco, Nazca, Australia, Philippine Sea and Pacific plates). Beneath slower plates, plate-motion parallel anisotropy is only observed locally, which suggests that the mantle flow below these plates is not controlled by the lithospheric motion (a minimum plate velocity of around 4cmyr -1 is necessary for a plate to organize the flow in its underlying asthenosphere). The correlation of oceanic anisotropy with the actual plate motion in the shallow lithosphere is very weak. A better correlation is obtained with the fossil accretion velocity recorded by the gradient of local seafloor age. The transition between frozen-in and active anisotropy occurs across the typical age isotherm that defines the bottom of the thermal lithosphere around 1100°C. Under fast continents (mostly under Australia and India), the present-day velocity orients also the anisotropy in a depth range around 150-200 km depth which is not deeper than what is observed under oceans. © 2013 Elsevier B.V
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