Elastic full waveform inversion in vertically transversely isotropic media

Active seismic methods are the most powerful techniques to image the subsurface to detect minerals, oil and gas. Over the last decades, improvements of the seismic acquisition techniques have allowed to acquire long offset, low frequency data, which along with the increasing computational power have led to the blossom of seismic full waveform inversion that aims to interpret the waveform of various events. Acoustic full waveform inversion failed to provide a high resolution Earth model in Middle East, where there were alternating low velocity shale layers and high velocity carbonate layers. To improve the resolution, the Earth model of Middle East is proposed to be represented as vertically transversely isotropic (VTI) media. There are two major challenges: the surface waves and the multi-parameter inversions. For the first challenge, the free surface boundary condition is modified and the surface waves are not generated in the forward simulation. The second challenge is the main topic of this study. Theoretical analysis of the sensitivity parameters, also known as radiation pattern analysis, was conducted at first. Then, several inversion tests with a Middle East model was conducted. The parameterization with a full-angle-sensitivity parameter produced the best inversion. To move forward, the issue of insufficient initial model was also studied. Wave equation tomography and full waveform inversion was combined to deal with the cycle skipping issue. Composition du jury : Monsieur PLESSIX René-Edouard - Chercheur - SHELL - Directeur de thèse Monsieur SINGH Satish - Physicien - IPGP-Paris - Codirecteur Monsieur BROSSIER Romain - Assistant Professor - Université - Grenoble - Rapporteur Monsieur BOHLEN Thomas - Professeur - Karlsruher Institut für Technologie (Allemagne) - Rapporteur Monsieur MONTAGNER Jean-Paul - Professeur des universités - Université - Paris 7 - Paris Diderot - Membre Madame RIBODETTI-OPERTO Alessandra- Chargé de recherche - IRD- Membre Monsieur FICHTNER Andreas- Professeur - ETH Zürich- Membre