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Analyse de vitesse par migration : choix des paramètres utilisateurs et introduction des ondes transmises

Abstract : Seismic imaging is the technique used to determine the structures of the subsurface from seismic signals. One of the most important parameters is the velocity model, that can be split into the macromodel controlling the kinematics of wave propagation and velocity perturbations. Migration builds the image of velocity perturbation for a given macromodel. Migration Velocity Analysis estimates the quality of the macromodel with an objective function measuring the focusing in the image domain. The gradient of this objective function with respect to the macromodel allows to find the optimal macromodel in an iterative way. The method has been improved recently by replacing the migration operator by the asymptotic inverse in the subsurface offset domain. In this thesis, we show that the quality of the gradient is sensitive to the user parameters. We provide practical guidelines to ensure proper gradient. These guidelines are applied to the synthetic Marmousi model. Recent developments propose to take into account the transmitted waves. We compare different strategies for combining the two different kinds of waves and recommend to apply a separate workflow. We apply the method to a marine real data set provided by Total. We propose a two-step workflow: after a first try of several iterations, we adjust the parameters and restart the iterations.
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Submitted on : Tuesday, February 9, 2021 - 10:42:10 AM
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  • HAL Id : tel-03135664, version 1

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Tianyou Zhou. Analyse de vitesse par migration : choix des paramètres utilisateurs et introduction des ondes transmises. Géophysique [physics.geo-ph]. Université Paris sciences et lettres, 2020. Français. ⟨NNT : 2020UPSLM046⟩. ⟨tel-03135664⟩

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