Suchergebnisse

Volcanic crisis management is a marginal study subject, whatever the research field. The complex nature of volcanic phenomena (multiple hazards, uncertainty of forecast), the lack of conceptual and methodological frameworks to study such crises, the reduced opportunities of experiencing volcanic crises, and the fact that Earth scientists focus on the hazard are all the reasons behind this lack of commitment. The objective of this thesis is to make up for some of these shortcomings by building up information on ways to manage crises. It provides post-crisis analysis about the management of the eruptive crisis of May 2006 at Karthala volcano (Grande Comore), and of April 2007 at the Piton de la Fournaise (La Reunion island). It also contains another analysis about the management of lahars subsequent to the explosive eruptions in 2005 in Grande Comore. These study case on personal experiences of analysed crises, then on investigations undertaken with local authorities, scientist, media and population. They highlight, amongst other things, a blatant lack of resources, information and training of all agents on both islands. The cause for such dysfunctioning factors are looked into. The analysis reveals the importance of human, cultural, political, socioeconomic, and territorial components in responding to crises. Finally, this thesis suggests tools and approaches to improve crisis management on both islands. ; La gestion des crises volcaniques constitue un sujet d'étude marginal, tous les domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitudes des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle propose ainsi des RETours d'Expérience sur la gestion de crises éruptives survenues en mai 2006 au Karthala (Grande Comore), et en avril 2007 au Piton de la Fournaise (La Réunion). S'y ajoute un RETEX sur la gestion des lahars consécutifs aux éruptions explosives de 2005 en Grande Comore. Ces cas d'étude reposent sur le vécu direct des crises analysées, puis sur un travail d'enquête auprès des autorités, scientifiques, médias et populations. Ils mettent entre autres en évidence un manque caractérisé de moyens, d'information et de formation de l'ensemble des acteurs sur les deux îles. Les causes profondes des facteurs de dysfonctionnement sont ensuite recherchées. L'analyse révèle le poids des composantes humaines, culturelles, politiques, socioéconomiques et territoriales dans les réponses apportées face aux crises. Enfin, cette thèse propose des outils et des approches pour améliorer la gestion des crises sur les deux îles.

Volcanic crisis management is a marginal study subject, whatever the research field. The complex nature of volcanic phenomena (multiple hazards, uncertainty of forecasts), the lack of conceptual and methodological frameworks to study such crises, the reduced opportunities of experiencing volcanic crises, and the fact that Earth scientists focus on the hazard are all reasons behind this lack of commitment. The objective of this thesis is to make up for some of these shortcomings by building up information on ways to manage crises. It provides post-crisis analysis about the management of the eruptive crises of May 2006 at Karthala volcano (Grande Comore), and of April 2007 at the Piton de la Fournaise (La Reunion island). It also contains another analysis about the management of lahars subsequent to the explosive eruptions in 2005 in Grande Comore. These study cases rely first on personal experiences of analysed crises, then on investigations undertaken with local authorities, scientists, media and population. They highlight, amongst other things, a blatant lack of resources, information and training of all agents on both islands. The causes for such dysfunctioning factors are then looked into. The analysis reveals the importance of human, cultural, political, socioeconomic and territorial components in responding to crises. Finally, this thesis suggests tools and approaches to improve crisis management on both islands. ; La gestion des crises volcaniques constitue un sujet d'étude marginal, tous domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitude des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle ...

Volcanic crisis management is a marginal study subject, whatever the research field. The complex nature of volcanic phenomena (multiple hazards, uncertainty of forecast), the lack of conceptual and methodological frameworks to study such crises, the reduced opportunities of experiencing volcanic crises, and the fact that Earth scientists focus on the hazard are all the reasons behind this lack of commitment. The objective of this thesis is to make up for some of these shortcomings by building up information on ways to manage crises. It provides post-crisis analysis about the management of the eruptive crisis of May 2006 at Karthala volcano (Grande Comore), and of April 2007 at the Piton de la Fournaise (La Reunion island). It also contains another analysis about the management of lahars subsequent to the explosive eruptions in 2005 in Grande Comore. These study case on personal experiences of analysed crises, then on investigations undertaken with local authorities, scientist, media and population. They highlight, amongst other things, a blatant lack of resources, information and training of all agents on both islands. The cause for such dysfunctioning factors are looked into. The analysis reveals the importance of human, cultural, political, socioeconomic, and territorial components in responding to crises. Finally, this thesis suggests tools and approaches to improve crisis management on both islands. ; La gestion des crises volcaniques constitue un sujet d'étude marginal, tous les domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitudes des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle propose ...

Volcanic crisis management is a marginal study subject, whatever the research field. The complex nature of volcanic phenomena (multiple hazards, uncertainty of forecast), the lack of conceptual and methodological frameworks to study such crises, the reduced opportunities of experiencing volcanic crises, and the fact that Earth scientists focus on the hazard are all the reasons behind this lack of commitment. The objective of this thesis is to make up for some of these shortcomings by building up information on ways to manage crises. It provides post-crisis analysis about the management of the eruptive crisis of May 2006 at Karthala volcano (Grande Comore), and of April 2007 at the Piton de la Fournaise (La Reunion island). It also contains another analysis about the management of lahars subsequent to the explosive eruptions in 2005 in Grande Comore. These study case on personal experiences of analysed crises, then on investigations undertaken with local authorities, scientist, media and population. They highlight, amongst other things, a blatant lack of resources, information and training of all agents on both islands. The cause for such dysfunctioning factors are looked into. The analysis reveals the importance of human, cultural, political, socioeconomic, and territorial components in responding to crises. Finally, this thesis suggests tools and approaches to improve crisis management on both islands. ; La gestion des crises volcaniques constitue un sujet d'étude marginal, tous les domaines de recherche confondus. La complexité des phénomènes volcaniques (aléas multiples, incertitudes des prévisions), l'absence de cadre conceptuel et méthodologique établi pour l'étude des crises, les opportunités réduites de vivre des crises volcaniques, et la focalisation des chercheurs en sciences de la Terre sur l'aléa sont autant de raisons qui expliquent ce manque d'engagement. Cette thèse a pour objectif de combler partiellement ces lacunes en capitalisant des analyses sur les modes de gestion des crises. Elle propose ...

International audience ; Although Karthala volcano in Grande Comore Island has erupted four times since 2005, the government and the local population still remain unprepared for a major eruptive crisis. The reasons for this lack of preparation lie in a deep tangle of political, socio-economic, cultural, and environmental factors. Consequently, the population accepts the volcanic threat in different ways and to different levels. The ways in which Comorians deal with this threat lead to important changes in their society (eg social links evolving, exposure to volcanic hazards in exchange for some improvements in daily life, and easier access to resources). On a national scale, deep structural adjustments are required in order to reduce vulnerability sustainably.

International audience ; Although Karthala volcano in Grande Comore Island has erupted four times since 2005, the government and the local population still remain unprepared for a major eruptive crisis. The reasons for this lack of preparation lie in a deep tangle of political, socio-economic, cultural, and environmental factors. Consequently, the population accepts the volcanic threat in different ways and to different levels. The ways in which Comorians deal with this threat lead to important changes in their society (eg social links evolving, exposure to volcanic hazards in exchange for some improvements in daily life, and easier access to resources). On a national scale, deep structural adjustments are required in order to reduce vulnerability sustainably.

International audience ; Although Karthala volcano in Grande Comore Island has erupted four times since 2005, the government and the local population still remain unprepared for a major eruptive crisis. The reasons for this lack of preparation lie in a deep tangle of political, socio-economic, cultural, and environmental factors. Consequently, the population accepts the volcanic threat in different ways and to different levels. The ways in which Comorians deal with this threat lead to important changes in their society (eg social links evolving, exposure to volcanic hazards in exchange for some improvements in daily life, and easier access to resources). On a national scale, deep structural adjustments are required in order to reduce vulnerability sustainably.

International audience ; Although Karthala volcano in Grande Comore Island has erupted four times since 2005, the government and the local population still remain unprepared for a major eruptive crisis. The reasons for this lack of preparation lie in a deep tangle of political, socio-economic, cultural, and environmental factors. Consequently, the population accepts the volcanic threat in different ways and to different levels. The ways in which Comorians deal with this threat lead to important changes in their society (eg social links evolving, exposure to volcanic hazards in exchange for some improvements in daily life, and easier access to resources). On a national scale, deep structural adjustments are required in order to reduce vulnerability sustainably.

PurposeFollowing the 26 December 2004 tsunami, Planet Risk NGO took part in the international research program TSUNARISK and ATIP‐CNRS Jeune Chercheur. The aim of this paper is to encourage the development of tsunami‐resilient communities essentially through educative actions.Design/methodology/approachThe tsunami risk in Indonesia was assessed by researchers. Planet Risk then used scientific findings and advice for building adapted prevention actions among Javanese populations.FindingsMany people could have survived if they had received a basic knowledge of tsunamis. The Indonesian public as well as local authorities must be educated to face tsunami risk. To be efficient, this education must be adapted to local cultural and geographical characteristics. Collaboration between researchers and practitioners is a good means of reaching such an objective.Originality/valueThe paper is the result of a two‐year successful collaboration between interdisciplinary scientific teams and an NGO team. It demonstrates that an efficient prevention scheme can be implemented through this kind of collaboration. To the authors' knowledge it is the first time that such tsunami education programmes have been led in Indonesia.

International audience ; The pre-colonial history (i.e. before the 16th century) of Tonga and West Polynesia still suffers from major gaps despite significant scientific advances in recent years, particularly in the field of archaeology. By the 14th century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and they are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring chiefdoms. However, the hypothesis of a major natural disaster was rarely suggested up to now, while field evidence points to the occurrence of a very large tsunami in the past, including the presence of numerous megablocks that were deposited by a "red wave" (or peau kula, which also mean tsunami in the Tongan language) according to a local myth. Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that a large tsunami inundated large areas of Tongatapu island in the mid-15th century with runup heights up to 30 m, and that the Tu'i Tonga kingdom was severely impacted by this event. We also discuss the likely sources of this tsunami.

International audience ; The pre-colonial history (i.e. before the 16th century) of Tonga and West Polynesia still suffers from major gaps despite significant scientific advances in recent years, particularly in the field of archaeology. By the 14th century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and they are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring chiefdoms. However, the hypothesis of a major natural disaster was rarely suggested up to now, while field evidence points to the occurrence of a very large tsunami in the past, including the presence of numerous megablocks that were deposited by a "red wave" (or peau kula, which also mean tsunami in the Tongan language) according to a local myth. Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that a large tsunami inundated large areas of Tongatapu island in the mid-15th century with runup heights up to 30 m, and that the Tu'i Tonga kingdom was severely impacted by this event. We also discuss the likely sources of this tsunami.

International audience ; The pre-colonial history (i.e. before the 16th century) of Tonga and West Polynesia still suffers from major gaps despite significant scientific advances in recent years, particularly in the field of archaeology. By the 14th century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and they are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring chiefdoms. However, the hypothesis of a major natural disaster was rarely suggested up to now, while field evidence points to the occurrence of a very large tsunami in the past, including the presence of numerous megablocks that were deposited by a "red wave" (or peau kula, which also mean tsunami in the Tongan language) according to a local myth. Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that a large tsunami inundated large areas of Tongatapu island in the mid-15th century with runup heights up to 30 m, and that the Tu'i Tonga kingdom was severely impacted by this event. We also discuss the likely sources of this tsunami.

International audience ; The pre-colonial history (i.e. before the 16th century) of Tonga and West Polynesia still suffers from major gaps despite significant scientific advances in recent years, particularly in the field of archaeology. By the 14th century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and they are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring chiefdoms. However, the hypothesis of a major natural disaster was rarely suggested up to now, while field evidence points to the occurrence of a very large tsunami in the past, including the presence of numerous megablocks that were deposited by a "red wave" (or peau kula, which also mean tsunami in the Tongan language) according to a local myth. Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that a large tsunami inundated large areas of Tongatapu island in the mid-15th century with runup heights up to 30 m, and that the Tu'i Tonga kingdom was severely impacted by this event. We also discuss the likely sources of this tsunami.

International audience ; The pre-colonial history (i.e. before the 16th century) of Tonga and West Polynesia still suffers from major gaps despite significant scientific advances in recent years, particularly in the field of archaeology. By the 14th century, the powerful Tu'i Tonga kingdom united the islands of the Tongan archipelago under a centralised authority and, according to tradition, extended its influence to neighbouring island groups in the Central Pacific. However, some periods of deep crisis were identified, e.g. in the mid- 15th century, marked by an abrupt cessation of inter-archipelago migration on the deep seas in the Pacific, significant cultural changes, and a decrease in accessible natural resources. The origins of these disturbances are still debated, and they are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring chiefdoms. However, the hypothesis of a major natural disaster was rarely suggested up to now, while field evidence points to the occurrence of a very large tsunami in the past, including the presence of numerous megablocks that were deposited by a "red wave" (or peau kula, which also mean tsunami in the Tongan language) according to a local myth. Drawing on a body of new evidence from sedimentary signatures and radiocarbon dating of charcoal and marine bioclasts, geomorphology, and sedimentology, in support of previously published archaeological data, we argue that a large tsunami inundated large areas of Tongatapu island in the mid-15th century with runup heights up to 30 m, and that the Tu'i Tonga kingdom was severely impacted by this event. We also discuss the likely sources of this tsunami.

Formalised elicitation of expert judgements has been used to help tackle several problematic societal issues, including volcanic crises and pandemic threats. We present an expert elicitation exercise for Piton de la Fournaise volcano, La Réunion island, held remotely in April 2021. This involved 28 experts from nine countries who considered a hypothetical effusive eruption crisis involving a new vent opening in a high-risk area. The tele-elicitation presented several challenges, but is a promising and workable option for application to future volcanic crises. Our exercise considered an "uncommon" eruptive scenario with a vent outside the present caldera and within inhabited areas, and provided uncertainty ranges for several hazard-related questions for such a scenario (e.g. probability of eruption within a defined timeframe; elapsed time until lava flow reaches a critical location, and other hazard management issues). Our exercise indicated that such a scenario would probably present very different characteristics compared to recent eruptions, and that it is fundamental to include well-prepared expert elicitations in updated civil protection evacuation plans to improve disaster response procedures. ; This work was funded by the Agence National de la Recherche (ANR) through project Lava Advance into Vulnerable Areas (LAVA; ANR program: DS0902 2016; project: ANR-16CE39–0009). This is ANR-LAVA con- tribution n°21. This contribution is part of the European Commis- sion grant EVE (DG ECHO Ref: 826292). J.M. received funding from the IMAGINE ERC Grant No 804162 to support the development of this paper. A.T. was funded by the ClerVolc project - Programme 1 "Detection and characterization of volcanic plumes and ash clouds" funded by the French government 'Laboratory of Excellence' initiative. This is ClerVolc contribution n°532. A.T. was also partially funded by the by the French government IDEX-ISITE initiative 16- IDEX-0001 (CAP 20-25). ; Peer reviewed