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Imagerie tri-dimensionnelle de l'atténuation sismique du manteau terrestre

Abstract : 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.
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https://theses.hal.science/tel-01618777
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Submitted on : Wednesday, October 18, 2017 - 2:56:08 PM
Last modification on : Saturday, April 2, 2022 - 3:48:19 AM
Long-term archiving on: : Friday, January 19, 2018 - 1:08:38 PM

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  • HAL Id : tel-01618777, version 1

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Alice Adenis. Imagerie tri-dimensionnelle de l'atténuation sismique du manteau terrestre. Sciences de la Terre. Université de Lyon, 2017. Français. ⟨NNT : 2017LYSEN037⟩. ⟨tel-01618777⟩

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