京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18654号 / 工博第3963号 / 新制||工||1610(附属図書館) / 31568 / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 田村 正行, 准教授 須﨑 純一, 准教授 横松 宗太 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Natural hazards cause enormous amounts of damage worldwide every year. Since 1994 more than 1.35 billion people have lost their lives and more than 116 million homes have been damaged. Understanding of disaster risk implies knowledge about vulnerability, capacity, exposure of persons and assets, hazard characteristics and the environment. Quantitative damage assessments are a fundamental part of disaster risk management. There are, however, substantial challenges when quantifying damage which depends on the diversity of hazards and the fact that one hazardous event can negatively impact a society in multiple ways. The overall aim of the thesis is to analyze the relationship between climate-related natural hazards and subsequent damage for the purpose of improving the prerequisite for quantitative risk assessments in the future. The thesis concentrates on two specific types of consequences due to two types of hazards, 1) damage to buildings caused by lake floods, and 2) loss of lives caused by quick clay landslides.  Several causal relationships were established between risk factors and the extent of damages. Lake water levels increased the probability of structural building damage. Private damage reducing measures decreased the probability of structural building damage. Extent of damage decreased with distance to waterfront but increased with longer flood duration while prewar houses suffered lower flood damage compared to others. Concerning landslides, the number of fatalities increased when the number of humans in the exposed population increased. The main challenges to further damage estimation are data scarcity, insufficient detail level and the fact that the data are rarely systematically collected for scientific purposes. More efforts are needed to create structured, homogeneous and detailed damage databases with corresponding risk factors in order to further develop quantitative damage assessment of natural hazards in a Nordic perspective. / Naturolyckor orsakar enorma mängder skador över hela världen varje år. Under åren 1994-2013 förlorade mer än 1,35 miljoner människor sina liv och mer än 116 miljoner hem skadades. Förståelse av risk för naturolyckor innebär kunskap om sårbarhet, kapacitet, exponering av personer och tillgångar, hot och miljö. Kvantitativa skadebedömningar, som är en viktig del av riskbedömningar, omfattas av stora utmaningar som grundar sig i hotens mångfaldighet och det faktum att en naturolycka kan påverka ett samhälle negativt på många olika sätt. Det övergripande syftet med avhandlingen är att analysera förhållandet mellan naturkatastrofer och potentiellt påföljande skador i syfte att förbättra förutsättningarna för kvantitativa riskbedömningar i framtiden. Avhandlingen koncentrerar sig på två typer av naturolyckor med specifika konsekvenser, 1) skador på byggnader till följd av sjö-översvämningar, och 2) förlust av liv orsakat av lerskred. Flera orsakssamband mellan riskfaktorer och omfattning av skador har identifierats. Sjöarnas vattennivåer ökade sannolikheten att drabbas av strukturell byggnadsskada, samtidigt som privat initierade åtgärder minskande sannolikheten.. När avstånd mellan sjö och byggnad ökade minskade omfattningen av översvämningsskador, men ökade ju längre sjööversvämningen varade. Hus byggda före 1940 fick mindre skador jämfört med andra hus. Andelen dödsfall i samband med skred i kvicklera ökade när antal människor i den exponerade befolkningen ökade. Den största utmaningen i att förbättra dagens kvantitativa skadebedömningar är den rådande databristen vad gäller förluster och tillhörande riskfaktorer. Denna brist beror på otillgänglig skadedata, bristande detaljnivå på skadedata och tillhörande risk faktorer, och att uppgifterna sällan samlas systematiskt i syfte att studera kausalitet. / The overall aim of the thesis is to analyze the relationship between climate-related natural hazards and subsequent damage for the purpose of improving the prerequisite for quantitative risk assessments in the future. The thesis concentrates on two specific types of hazards with specific types of consequences, 1) damage to buildings caused by lake floods, and 2) loss of lives caused by quick clay landslides.  Several causal relationships were established between risk factors and the extent of damages. Lake water levels increased the probability of structural building damage. Private damage reducing measures decreased the probability of structural building damage. Extent of damage decreased with distance to waterfront but increased with longer flood duration while prewar houses suffered lower flood damage compared to others. Concerning landslides, the number of fatalities increased when the number of humans in the exposed population increased. The main challenges to further damage estimation are data scarcity, insufficient detail level and the fact that the data are rarely systematically collected for scientific purposes.

Afim de se avaliar a dinâmica geomorfológica e social do município de Ubatuba, litoral norte do Estado de São Paulo, a pesquisa procurou levantar dados multidisciplinares das questões envolvidas, para a partir de então elaborar um banco de dados georreferenciados. A análise conjunta dos tipos de rocha, tipos de formas de relevo, dos graus de declividade, da concentração de aspectos morfotectônicos e o tipo de ocupação e concentração das distribuições urbanas do município culminou em um mapa de Risco Potencial de Acidentes Naturais. Os aspectos apresentados, quanto à avaliação de lineamentos, avaliação atualizada da distribuição censitária da região, e a inter-relação dos dados físicos e sociais, constituem aprofundamento do arcabouço fundamental para o pleno e racional desenvolvimento do município e região. Procurando estabelecer diálogo entre os dados concluídos e a sociedade que sofre com os riscos avaliados em Ubatuba, a pesquisa buscou que as avaliações sobre o material cartográfico final fossem discutidas por setores, divididos pelas sub-bacias que compõem o município. Desta forma, a apresentação dos dados obtidos apresenta um aspecto importante de individualização das questões particulares de cada bairro e cada área afetada, ou não, pelas diversas classes de risco avaliadas no mapa concluído / In order to assess the geomorphological and social dynamics of Ubatuba, northern coast of São Paulo, the research sought to raise multidisciplinary data of the issues involved, to thereafter prepare a georeferenced database. The municipality joint analysis of rock types, types of landforms, the degrees of slope, the concentration of morphotectonic aspects, occupancy type and concentration of urban distributions culminated in a Map of Potential Hazard of Natural Accidents. The aspects, regarding the evaluation guidelines, updated review of census region distribution, and the interrelationship of physical and social data, are deepening the fundamental framework for the full and rational development of the municipality and region. Seeking to establish dialogue between the concluded data and society that suffers from the assessed risks in Ubatuba, the research sought that evaluations on the final cartographic material were discussed by sectors, divided by sub-basins that make up the municipality. Thus, the presentation of data presents an important aspect of differentiating the particular issues of each neighborhood and each affected area, or not, for various categories evaluated in the final map

No description available.

Afim de se avaliar a dinâmica geomorfológica e social do município de Ubatuba, litoral norte do Estado de São Paulo, a pesquisa procurou levantar dados multidisciplinares das questões envolvidas, para a partir de então elaborar um banco de dados georreferenciados. A análise conjunta dos tipos de rocha, tipos de formas de relevo, dos graus de declividade, da concentração de aspectos morfotectônicos e o tipo de ocupação e concentração das distribuições urbanas do município culminou em um mapa de Risco Potencial de Acidentes Naturais. Os aspectos apresentados, quanto à avaliação de lineamentos, avaliação atualizada da distribuição censitária da região, e a inter-relação dos dados físicos e sociais, constituem aprofundamento do arcabouço fundamental para o pleno e racional desenvolvimento do município e região. Procurando estabelecer diálogo entre os dados concluídos e a sociedade que sofre com os riscos avaliados em Ubatuba, a pesquisa buscou que as avaliações sobre o material cartográfico final fossem discutidas por setores, divididos pelas sub-bacias que compõem o município. Desta forma, a apresentação dos dados obtidos apresenta um aspecto importante de individualização das questões particulares de cada bairro e cada área afetada, ou não, pelas diversas classes de risco avaliadas no mapa concluído / In order to assess the geomorphological and social dynamics of Ubatuba, northern coast of São Paulo, the research sought to raise multidisciplinary data of the issues involved, to thereafter prepare a georeferenced database. The municipality joint analysis of rock types, types of landforms, the degrees of slope, the concentration of morphotectonic aspects, occupancy type and concentration of urban distributions culminated in a Map of Potential Hazard of Natural Accidents. The aspects, regarding the evaluation guidelines, updated review of census region distribution, and the interrelationship of physical and social data, are deepening the fundamental framework for the full and rational development of the municipality and region. Seeking to establish dialogue between the concluded data and society that suffers from the assessed risks in Ubatuba, the research sought that evaluations on the final cartographic material were discussed by sectors, divided by sub-basins that make up the municipality. Thus, the presentation of data presents an important aspect of differentiating the particular issues of each neighborhood and each affected area, or not, for various categories evaluated in the final map

Natural hazards are an important way for individuals to experience consequences of climate change. It has therefore been suggested that natural hazards could act as opportunities to increase individuals’ concerns about, and willingness to act on, climate change. The empirical evidence within the field is however mixed. Moreover, the research field is drawn back by methodological shortcomings, as studies rarely have been able to make valid pre-hazard assessments. A more accurate estimation of a possible causal effect is enabled in this study, as a survey mapping climate change opinions was conducted in Germany when the country was hit by a rare and severe hazard event, namely the European Floods. This provides an opportunity to examine the effect of hazard exposure on individuals’ levels of climate change concerns and willingness to adopt climate change-related actions. Three sets of hypotheses are tested using two-sample t-tests. The findings suggest that natural hazards have limited potential to act as teachable moments; climate change concerns may increase, but not willingness to take action. Political ideology is found to slightly moderate the effect between hazard exposure and climate change concerns, but only among right-leaning individuals. These findings make an important contribution to a mixed research field.

Cette étude porte sur la perception antique des catastrophes naturelles, les moyens de gestion et les représentations religieuses. Elle se fonde essentiellement sur l'interprétation des documents littéraires et épigraphiques, mais, dans une logique interdisciplinaire, elle n'exclue pas d'intégrer la documentation archéologique et les résultats obtenus, dans certains cas, par la géomorphologie. L'emploi des expressions « catastrophes naturelles » et « risques naturels » repose sur une définition récente portée par les géographes contemporains : un risque est le produit d'un aléa naturel – la probabilité d'occurence d'un phénomène physique – et de la vulnérabilité d'une société – les facteurs aggravants et la capacité de résilience d'une communauté civique. L'application de ce concept au monde des cités grecques, depuis l'époque classique jusqu'au Haut Empire romain, invite à tenir compte des évolutions notables qui ont marqué les processus de gestion des risques et les discours, scientifiques ou religieux, portant sur les bouleversements majeurs survenus à la surface du globe. L'enquête s'articule ainsi autour de deux axes principaux : le premier établit les impacts catastrophiques, autrement dit les types de conséquences qu'un aléa naturel a pu produire sur une société antique, inhumation des victimes, soins apportés aux survivants, destructions des édifices urbains, modifications et altérations des paysages ainsi que les difficultés et les crises économiques consécutives aux événements dévastateurs ; dans un second temps, cette étude entreprend d'analyser les observations et les théories antiques portant sur les catastrophes naturelles, autant que les discours et les actes religieux. En parallèle, l'enjeu de cette enquête est de répondre à une question essentielle : les Grecs ont-ils subi les catastrophes ou ont-ils cherché à se prémunir efficacement contre la fréquence de certains risques naturels ? / This thesis deals with the perception, management and religious thoughts of natural hazards in Antiquity. It is based essentially on epigraphics and literary sources, but includes archaeological and geomorphological documentation. Natural hazards and risks are two recent notions, coming from geographic studies. To apply these concepts to the Greek world, from the Classical Period to the Roman Empire, contributes to our knowledges of these societies, pointing out the chronological evolutions of the scientific discourses and the religious thoughts. This study is organized in two main parts ; the first dealing with the consequences of natural hazards (burial of victims, destruction of buildings, modifications of landscapes and economic crisis) and the second, the analysis of theories about natural hazards as well as the religious representations and practices. Last but not least, one of the most important questions that this thesis tries to answer is "Did Greek society manage the risks or did it fall victim to doomsday ?"

Les éboulements rocheux de volume intermédiaire (103-105 m3) posent un problème sérieux dans les régions montagneuses en raison de leur fréquence d'occurrence relativement élevée et de leur fort pouvoir destructeur. En conséquence, il est difficile de mener des travaux de protection pour réduire l'aléa, ce qui souligne le besoin de techniques de suivi et d'alerte précoce avant la rupture. Après l'éboulement, peu d'informations quantitatives sont disponibles sur la phase de propagation en raison de la soudaineté du phénomène et de sa localisation dans des pentes raides et difficiles d'accès. Dans ce travail de thèse, une approche expérimentale est proposée pour extraire des informations à partir d'enregistrements de signaux sismiques durant les phases pré- et post-rupture d'éboulements.La première partie de ce travail vise à tester la pertinence des vibrations ambiantes pour le suivi temporel de la réponse dynamique de compartiments rocheux lors de la phase pré-rupture. Cette technique (couramment employée en génie civil pour le suivi de l'intégrité des structures) permet d'extraire les fréquences de résonance d'une structure, dont la décroissance peut traduire l'endommagement. Une étude antérieure menée sur une colonne calcaire instable a montré une décroissance d'environ 30% de la fréquence fondamentale de résonance (f1) environ deux semaines avant la rupture, interprétée comme une diminution de la rigidité du contact avec le massif stable adjacent. / Mid-size rockfalls (103-105 m3) represent a substantial hazard in mountainous areas, because of relative high rate of occurrence and destructive power. Consequently, few protection means can be applied, emphasizing the need for monitoring techniques and early warning prior to the collapse. After the rupture, quantitative information on the rockfall propagation phase is scarce, owing to their suddenness and location in steep and rugged slopes. In this thesis work, an experimental approach is proposed to derive valuable information from seismic records during rockfall pre-rupture and post-rupture phases. The first part of this work aims at testing the applicability of the ambient vibration technique to monitor unstable rock compartments dynamic response in the pre-rupture phase. This technique (commonly employed in civil engineering for structural health monitoring) reveals the resonant frequencies of a structure, a decrease in frequency revealing potential damage. A previous case study of an unstable limestone compartment brought to light a #30% decrease in fundamental resonant frequency (f1) two weeks before the collapse. Following this innovative work, we selected and instrumented four prone-to-fall medium-size rock compartments located in the Occidental Alps, showing various geological contexts (limestones, argillite and shale-sandstone series), deformation patterns and failure mechnisms. Ambient vibrations recorded on-site revealed caracteristic seismic noise features. Spectral peaks were observed and attributed to resonant frequencies of the rock compartments, the fundamental resonant frequency (f1) showing clear polarization parallel to the line of maximum slope gradient, and perpendicular to the main bounding fracture observed at most of the sites. Similar findings were made for an unstable rock compartment located in a volcanic caldera, characterized by rapid morphological changes and intense rockfall activity. The dynamic response of the rear fracture network was explored, showing that spectral content of seismic noise is controlled by the caldera structure in the 0.5-5 Hz range. The direction of vibration is polarized perpendicularly to the fractures, while vibration amplitudes are linked to compartment uncoupling from the rock massif. In this case, the physical origin of seismic noise amplification may be due to complex 2D or 3D resonance effects. For the four alpine sites, the fundamental frequency f1 was monitored over more than one year, showing fluctuations clearly correlated with temperature oscillations. The thermal control over f1 is highly complex, showing both positive and negative correlations, depending on site morphology and destructuration, as well as on the studied oscillations periods (daily or seasonal). No change in fundamental frequency resulting from damage was observed over this time span. One site, characterized by intense rock fracturing and a deep-open rear fracture, showed high f1 sensitivity to temperature changes. Thermo-mechanical numerical simulations revealed that both material contraction-dilation and thermal dependancy of the elastic modulus control f1 fluctuations. In addition, high amplitude seasonal f1 oscillations were explained by ice formation in the rear fracture. A criterion was developped to separate thermal-induced f1 fluctuations from damage effects, under the hypothesis that thermal sensitivity of a rock compartment increases towards failure. The second part of this work relates to the post-rupture phase of rockfalls. The seismic records generated by two mid-size rockfalls {one natural, one provoked{ that occured in the same place were analyzed, showing complex enveloppe and spectrogram features. Both events showed close magnitude, duration and spectral content. The seismic signals of the provoked event were calibrated using video shots, allowing estimation of fallen material velocity during the successive propagation phases.

La menace représentée par le changement climatique, et en particulier l’élévation du niveau de la mer, sur les pays entièrement composés d’atolls est largement médiatisée. La République de Kiribati est un pays atollien situé dans l’océan Pacifique, peuplé par 100 000 habitants. Au cours des derniers siècles, les communautés atolliennes de Kiribati ont développé un système de gestion des ressources naturelles qui a assuré leur survie. Depuis quelques décennies, la mondialisation est cause de mutations rapides, en particulier dans le mode de vie et dans la relation des communautés atolliennes à leur environnement naturel. Étant donné le caractère fortement intégré du système sociétal et de l’écosystème dans les atolls, cette thèse aborde la question de l’avenir des pays atolliens dans le contexte du changement climatique par l’étude de la résilience de leurs systèmes socio-écologiques. La résilience d’un système correspond à sa capacité à absorber des perturbations et à se réorganiser tandis qu’il subit des changements tout en conservant la même fonction, structure, identité et les mêmes rétroactions. Cette thèse postule qu’une estimation de la résilience des systèmes socio-écologiques aux perturbations d’origine météo-marine nécessite au préalable une analyse de leur résilience générale. De telles estimations s’appuient sur des modèles conceptuels réalisés à partir de résultats d’entretiens et d’enquêtes menés à Kiribati, et sur l’analyse d’images aériennes. L’avenir des pays atolliens est discuté en envisageant différents scénarios : l’adaptation, la transformation, la migration et l’effondrement. / The threats to states entirely composed of atolls from climate change and associated sea-level rise have been widely publicized. The Republic of Kiribati is an atoll country situated in Pacific Ocean settled by 100,000 inhabitants. Over the past centuries, the atoll communities of Kiribati have developed natural resource management systems that have enabled their survival. Over the past decades, globalization has caused rapid changes, especially regarding lifestyles and relationships of atoll communities to their natural environment. Given the highly integrated nature of the societal system and the ecosystem in the atolls, this thesis addresses the question of the future of atoll countries in the context of climate change by studying the resilience of their social-ecological systems. Resilience is the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks. This thesis postulated that an assessment of social-ecological resilience of climate- and marine-related disturbances required a preliminary analysis of their general resilience. Such assessments are based on conceptual models made from interviews and surveys and from the analysis of aerial imagery. The future of atoll countries is discussed considering different scenario: adaptation, transformation, migration and collapse.

La surveillance d’un glissement de terrain vise à anticiper sa rupture pour réduire le risque d’accident. Elle s'opère généralement en mesurant les déplacements du sol. Ce travail propose une nouvelle technique de mesure de déplacement de glissements, flexible et à bas coût, basée sur l’utilisation d’étiquettes d’identification radiofréquence (RFID). La méthode de localisation d’étiquettes par différence de phase à 866 MHz est explorée en conditions extérieures et sur de longues durées. Cette étude a montré une détérioration de la mesure causée par les variations de température, d’humidité, de neige et de végétation. Après application de corrections, la précision de mesure a été améliorée, passant de ±20 cm à ±1 cm en conditions extérieures courantes. Cette technique fonctionne également en conditions neigeuses et en présence d’herbes hautes, mais avec une incertitude de mesure plus élevée (±8 et 4 cm respectivement). Ces erreurs de mesure sont provoquées par des effets de propagation, d’interférence multitrajets, et de per-turbations à proximité des antennes. Un système de mesure en continu a été déployé sur le glissement de terrain de Pont-Bourquin, en Suisse, pendant cinq mois. Ce dispositif a validé l’efficacité de la technique en conditions réelles. De plus, la mesure résiste bien aux intempéries et le dispositif demande peu de maintenance, en comparaison avec les techniques conven-tionnelles (extensomètre, GPS, station totale).Deux méthodes de mesure complémentaires aux déplacements ont ensuite été étudiées. La méthode de corrélation de vibrations ambiantes est prometteuse, mais n’a pas encore été utilisée en surveillance opérationnelle. Une étude bibliographique souligne plusieurs verrous à lever, tels que la correction des variations saisonnières et journalières, l’augmentation de la résolution temporelle, et le choix des paramètres de traitement adaptés au site surveillé. La méthode qui consiste à inverser une fonction de transfert entre des données de pluie et de déplacements est ensuite étudiée. Une inversion haute résolution de cette fonction est proposée. Elle permet d’identifier des comportements hydrologiques complexes (ex : infiltration à deux vitesses sur le site de Pont-Bourquin) et de mesurer leur évolution. Les avancées de cette thèse vont permettre d’améliorer la surveillance opérationnelle tout en réduisant son coût, répondant aux besoins des collectivités territoriales. / Landslide early-warning systems are based primarily on monitoring the displacement of the landslide. This work develops a new technique for monitoring these displacements, using radio-frequency identification (RFID) passive tags and phase-based location technique. This technique is deployed for the first time outdoors and for several months. Outdoor conditions revealed strong environmental influences due to temperature variations, moisture, snow and vegetation. These can cause a ±20 cm measurement uncertainty over a year, which is too large for landslide monitoring applications. The correction of these effects allows reaching the accuracy of ±1 cm under normal conditions, ±8 cm with snow and ±4 cm with dense high grass. The remaining effects due to snow and grass are explained by the influence of this material on the direct propagation, on the multipath interferences and on the antennas. This measurement system has been deployed on the Pont-Bourquin landslide for five months. The results validate the technique for landslide monitoring applications. The technique also shows the operational benefits of robustness to bad weather, easy maintenance and low-cost material, compared to conventional techniques (extensometer, GPS, total station).This thesis then studies two complementary monitoring methods that had recently been shown to provide precursors to landslide rupture. First, ambient seismic noise interferometry is used to detect a drop of shear-wave velocity prior to a rupture. The seismic method was studied in the literature to identify what must be developed to use this technique in an operational early-warning system. It requires getting rid of daily and seasonal environmental influences, choosing the processing parameters appropriate to the monitored landslide, and improving the temporal resolution below one day while keeping a stable enough signal. The other method consists of inverting an impulse response between rainfall and displacement rate, with a high resolution. It can shed light on complex infiltration processes (e.g. infiltration with two different delays at Pont-Bourquin) and detect their abnormal evolution across time. These developments should improve landslide operational monitoring with a low budget.