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Modélisation d'ondes sismo-acoustiques par la méthode des éléments spectraux : application à un séisme en Atlantique Nord

Abstract : For more than 2 decades, recording of hydroacoustic signals in the sopen channel (Sound Fixing And Ranging) has allowed the detection and localization of many low-magnitude earthquakes in the ocean. However the interpretation of these signals is still incomplete.The generation of acoustic waves, known as T-waves, resulting from the conversion of seismic waves into acoustic waves at the sea-bottom, and their propagation in the water column are not yet fully understood, which prevents to extract more information about the earthquakes they originate from. Here, we use numerical modelling to identify and understand the main environmental parameters and phenomena that control the generation and propagation of acoustic T-waves in the ocean. The proposed approach is a spectral element method, implemented in the code SPECFEM2D, which allows to address the problem in a comprehensive way taking into account the solid/fluid coupling (seismic propagation, conversion, acoustic propagation), velocity profiles of the waves in the crust and the ocean, and the moment tensor of the earthquake that defines the radiation pattern of the seismic source. Simulated acoustic signals present many similarities in the shape, duration, arrival times and amplitudes of the predicted T-waves with observed T-waves. Differences are likely due to the 2D representation of the problem and to the simplistic representation of the environment and of the seismic source.
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Guillaume Jamet. Modélisation d'ondes sismo-acoustiques par la méthode des éléments spectraux : application à un séisme en Atlantique Nord. Géophysique [physics.geo-ph]. Université de Bretagne occidentale - Brest, 2014. Français. ⟨NNT : 2014BRES0030⟩. ⟨tel-01091245v2⟩

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