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Suivi Sismologique De L'impact Des Cyclones Sur La Charge De Fond De Université de La Réunion – Laboratoire Géosciences Réunion – IPGP THÈSE Pour obtenir le grade de DOCTEUR D’UNIVERSITÉ Spécialité : Sismologie Par Alicia GONZALEZ Suivi sismologique de l’impact des cyclones sur la charge de fond de la Rivière des Pluies et de la Rivière du Mât à La Réunion Soutenue publiquement le 28 juin 2019, devant le jury composé de : Christel TIBERI Chargée de Recherche, Université de Montpellier Rapporteure Eric LAROSE Directeur de Recherche, ISTerre Grenoble Rapporteur Florent GIMBERT Chargé de Recherche, IGE Grenoble Examinateur Alain RECKING Chargé de Recherche, IRSTEA Grenoble Examinateur Jean-Lambert JOIN Professeur, Université de La Réunion Examinateur Fabrice R. FONTAINE Maitre de Conférence, Université de La Réunion Directeur Guilhem BARRUOL Directeur de Recherche, IPGP Co-Directeur Valérie FERRAZZINI Directeur de Recherche, IPGP Invitée Avant-propos Thèse réalisée au Laboratoire Géosciences Reunion (LGSR) bât. S1 15 Av. René Cassin CS 92003 97744 Saint-Denis Tél. : 0262938211 Web : https://geosciences.univ-reunion.fr/home Sous la direction de Fabrice Fontaine [email protected] et la co-direction de Guilhem Barruol [email protected] Financement Allocation sans contrat : soutien financier de la Région Réunion et de l’Union Européenne – Fonds européen de développement régional (FEDER) PO 2014-2020. Remerciements Ma première pensée va à Fabrice Fontaine, mon directeur de thèse, qui a eu confiance en mes capacités pour relever ce challenge. Fabrice, je te serai à jamais reconnaissante pour cette expérience unique. Je remercie ensuite mon co-directeur de thèse Guilhem Barruol pour son encadrement depuis Paris. Merci pour les nombreux conseils, corrections, propositions, les discussions essentielles qui m'ont souvent redonné confiance en mes raisonnements, merci de m'avoir accueilli à Paris dans une phase cruciale de production. Ces moments ont été de vrais moteurs pour avancer. Et évidemment, j'ai beaucoup appris. Un immense merci à Eric Delcher, alias MacGyric, ingénieur de notre laboratoire, auprès de qui j'ai acquis des compétences de terrain diversifiées et primordiales. Merci d'avoir appuyé mon apprentissage technique et d'avoir participé à développer mon sens pratique. Merci pour ton accompagnement sans failles sur le terrain ou au laboratoire, d'avoir toujours su trouver la solution pour régler les dysfonctionnements en temps et en heure. Je te remercie aussi d'avoir pris le temps d'écouter mes longs récits de chantiers interprétatifs. Dans la phase finale, merci d'avoir pris soin que le manuscrit avance dans les meilleures conditions. Un grand merci à Arnaud Burtin qui m'a reçu à l'IPGP à deux reprises pour la prise en main de ses codes et qui m'a transmis la sensibilité du sismologue environnemental. Je remercie vivement Céline Laborde, responsable du bureau d'études Stratagem974, qui a apporté son soutien avant même le début de la thèse en appuyant la demande de financement auprès de la Région Réunion puis en mettant à notre disposition du matériel (drone Phantom III, perche, appareil photo, capteurs sismiques, batteries, PC de modélisation, outillage) et du personnel pour effectuer des campagnes de terrain et du traitement d'images. Dans ce cadre, je remercie particulièrement Florian Durand (Ingénieur à Stratagem974) dont l'aide a été précieuse pour l'aspect stéréo-photogrammétrie dans la rivière des pluies et cela malgré son emploi du temps chargé. Je remercie Julien Bonnier de l'Office de l'Eau et François Bonnardot, côté MétéoFrance, pour leurs réponses systématiques à mes nombreuses demandes par mail ou par téléphone. Je remercie Alain Recking d'avoir fait le déplacement depuis Grenoble pour me former à la lecture de terrain pour l'analyse de la dynamique hydro-sédimentaire, de m'avoir appris à faire un échantillonnage granulométrique dans les règles de l'art. Merci également à Geneviève Lebeau, la technicienne du LGSR, de m'avoir accompagné à la Rivière des Pluies pour effectuer des relevés granulométriques suivants. Je remercie également Nicolas Villeneuve de m'avoir donné les clés, à Terre, pour réussir les prises de vue aériennes et de m'avoir confié son précieux appareil photo. Merci a lui d'avoir encadré le stage dédié à l'analyse de ces images. Mes remerciements vont également à Laurent Michon, directeur du LGSR, de s'être rendu disponible pour des discussions enrichissantes autour des interprétations des hystérésis, de m'avoir encouragée à ne pas lâcher la donnée et d'en puiser tout le jus jusqu'à la dernière goutte ! Je remercie aussi Jean-Lambert d'avoir répondu à mes questionnements hydrogéologiques. Un grand merci aux 4 stagiaires de l'Ecole Navale qui ont travaillé, dans le cadre de ma thèse, à améliorer la compréhension du contenu des enregistrements sismiques. Jules Bennistant, Maxence Guillon, Félix Hennion et Thibault Labadie, merci d'avoir produit des codes précieux à ma demande, vous êtes les meilleurs moussaillons ! Un merci particulier à Thibault avec qui nous avons discuté intensément et fait avancer le débat sur la discrimination des sources sismiques... Je remercie mes collègues doctorants Anthony Dofal et Bhavani Bénard de m'avoir accordé du temps lorsque j'avais besoin de conseils sur Illustrator et QGis. Vous êtes tellement bons ! Un immense merci à Cécile d'avoir relu ma thèse et d'avoir eu le regard critique nécessaire. Je te donne ton HDR ! Merci à Caro, Audrey et Matthieu d'avoir pris le temps de lire des passages de ma thèse pour me donner leur avis, à ma maman et Camille d'avoir cherché les fautes d'orthographes ainsi qu'à Jean-Momo de m'avoir épaulée pour la mise en page. Dans la phase finale de cette expérience de thèse, je remercie vivement mes rapporteurs Christel Tiberi et Eric Larose pour les remarques avisées qui ont participé à faire évoluer le manuscrit et pour leur enthousiasme quant au travail accompli. Merci également aux autres membres du jury pour les remarques et discussions intéressantes; Alain Recking, Florent Gimbert et Valérie Ferrazzini. J'ai eu la chance d'avoir des collaborateurs et des collègues de travail exceptionnels mais j'ai aussi vécu ces trois ans avec le soutien de près ou de loin de copains supers, d'amis fantastiques, de ma famille irremplaçable, et de mon cher amour. Julie, Cécile mes choupettes Audrey Caro vous êtes des femmes extraordinaires,et des wonderwomen et vouset m'avez, donné beaucoup de force, merci, je vous adore. Eric et Céline et leur enfants, David, John, Bhavani, Camille, Anthony, Sophie, Estelle, Chloé, Valentine, Elise, Nico touktouk, Océane, Thibault, Sarah et la famille Vyskoc, Galdrock et André, Doudou, Jean-Momo, Damien, Bert, Mât, Elisa, Jojo et Marine; je suis heureuse que vous vous soyez trouvés sur mon chemin ! Merci pour les bons moments de rigolades, de pleurs et de soutien sans faille. Mes cousines adorées, merci de m'avoir suivi de loin. Une pensée pour ma petite mamie Mélina qui avait grande hâte que je finisse mes études, "mais oui mais oui, la thèse est finie" !! Un merci infini à mes parents et mon frère que j'aime plus que tout de m'avoir aimé à la folie depuis toujours, d'avoir été si fiers de moi et d'avoir fait le déplacement plusieurs fois pour venir me soutenir sur place. Brice [Foucart 2019], à distance puis ensemble sur cette île, nous avons franchi les étapes les unes après les autres. Merci d'avoir partagé ma vie de thésarde, d'être resté à mes côtés malgré les difficultés. Merci de m'avoir fait beaucoup rire, de m'avoir comprise, soutenue, poussée et de m'avoir rendu heureuse. Merci à tous ceux qui ont su me donner des élans de motivation durant ces trois années difficiles. Un dernier merci au Maloya, au créole qui chante mieux que la cigale, merci aux reliefs, rivières, cascades, bassins, à l'océan, aux baleines, dauphins, à la pluie, aux couchers de soleil et surtout au magma ! La nature et la culture de cette île m'ont réchauffé le cœur, donné des frissons et des larmes aux yeux. Merci La Réunion ! " Ce qui est écrit sans peine est lu sans plaisir. " Louis-Philippe Robidoux ; Lueurs (1951) Table des matières Chapitre 1 - Introduction.................................................................................................................... 1 1.1 Préambule ........................................................................................................................................................1 1.2 Introduction.....................................................................................................................................................2 1.2.1 Contexte et problématique générale............................................................................................................. 2 1.2.2 Analyse du transport solide – Problématique........................................................................................... 4 Chapitre 2 - Contexte local et site d'étude ..................................................................................13 2.1 Contexte climatique de l'île....................................................................................................................13 2.1.1 Variabilité temporelle du climat ...................................................................................................................14 2.1.2 Variabilité spatiale du climat..........................................................................................................................15 2.1.3 Réponse hydrologique et torrentialité.......................................................................................................16
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