astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Interpolation spatiale de données circulaires : application au tsunami du 26 décembre 2004
In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order... more In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order to develop hydrodynamic model, we used geo-statistical tools to reconstruct the tsunami of December, 24th, 2004 at Banda Aceh (Indonesia). On a area of 20 km2, about 1000 angles were measured, based on impact of the wave. To simplify the modelling, we assume unicity of the wave. Classical spatial statistics cannot be used in this problem since (i) kriging is not invariant by rotation; (ii) the arithmetic mean cannot be used for circular data.We first review common adaptations of kriging to circular data. Drawbacks of these methods are illustrated on our example. Finally we extend circular data theory to spatial statistics
Interpolation spatiale de données circulaires : application au tsunami du 26 décembre 2004
In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order... more In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order to develop hydrodynamic model, we used geo-statistical tools to reconstruct the tsunami of December, 24th, 2004 at Banda Aceh (Indonesia). On a area of 20 km2, about 1000 angles were measured, based on impact of the wave. To simplify the modelling, we assume unicity of the wave. Classical spatial statistics cannot be used in this problem since (i) kriging is not invariant by rotation; (ii) the arithmetic mean cannot be used for circular data.We first review common adaptations of kriging to circular data. Drawbacks of these methods are illustrated on our example. Finally we extend circular data theory to spatial statistics
Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to e... more Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to evaluate the activity of a volcano, such as Merapi volcano where associated disaster risk is regularly taking lives. Within this framework, this study aime to detect localized deformation and change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset of 2012 and one UAV-dataset of 2014. The results show that during the period 2012-2014, the crater walls are 100 m to 120 m high above the crater floor at its maximum (North to East-South-East sector), while the West and North sector presents a topographic range of 40 to 80 m. During the period 2012 – 2014, the evolution of the crater rim around the dome is generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 E+04 m3 corresponding to a maximum -9 m...
Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to e... more Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to evaluate the activity of a volcano, such as Merapi volcano where associated disaster risk is regularly taking lives. Within this framework, this study aime to detect localized deformation and change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset of 2012 and one UAV-dataset of 2014. The results show that during the period 2012-2014, the crater walls are 100 m to 120 m high above the crater floor at its maximum (North to East-South-East sector), while the West and North sector presents a topographic range of 40 to 80 m. During the period 2012 – 2014, the evolution of the crater rim around the dome is generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 E+04 m3 corresponding to a maximum -9 m...
Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier i... more Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier islands are surprisingly resilient to extreme storm events. At present, little is known about barrier systems’ resilience to seismic events triggering tsunamis, co-seismic subsidence, and liquefaction. The objective of this study is, therefore, to investigate the morphological resilience of the barrier islands in responding to those secondary effects of seismic activity of the Sumatra–Andaman subduction zone and the Great Sumatran Fault system. Spatial analysis in Geographical Information Systems (GIS) was utilized to detect shoreline changes from the multi-source datasets of centennial time scale, including old topographic maps and satellite images from 1898 until 2017. Additionally, the earthquake and tsunami records and established conceptual models of storm effects to barrier systems, are corroborated to support possible forcing factors analysis. Two selected coastal sections possess ...
Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier i... more Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier islands are surprisingly resilient to extreme storm events. At present, little is known about barrier systems’ resilience to seismic events triggering tsunamis, co-seismic subsidence, and liquefaction. The objective of this study is, therefore, to investigate the morphological resilience of the barrier islands in responding to those secondary effects of seismic activity of the Sumatra–Andaman subduction zone and the Great Sumatran Fault system. Spatial analysis in Geographical Information Systems (GIS) was utilized to detect shoreline changes from the multi-source datasets of centennial time scale, including old topographic maps and satellite images from 1898 until 2017. Additionally, the earthquake and tsunami records and established conceptual models of storm effects to barrier systems, are corroborated to support possible forcing factors analysis. Two selected coastal sections possess ...
The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its re... more The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its reconstruction is essentially based on legends left by oral tradition, and by archaeological evidence somehow difficult to interpret. By the fourteenth 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-15 th century, marked by an abrupt cessation of interarchipelago 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 are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring states. However, the hypothesis of a major natural disaster was never suggested up to now. 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 the Tu'i Tonga kingdom was severely impacted by a megatsunami in the mid-15th century. We also discuss the likely sources of this event, which happened in an isolated region of the world before the European maritime "great discoveries". This tsunami could be the source of vivid local myths that strongly suggest that a giant wave covered almost the entire island of Tongatapu at one time.
The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its re... more The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its reconstruction is essentially based on legends left by oral tradition, and by archaeological evidence somehow difficult to interpret. By the fourteenth 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-15 th century, marked by an abrupt cessation of interarchipelago 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 are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring states. However, the hypothesis of a major natural disaster was never suggested up to now. 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 the Tu'i Tonga kingdom was severely impacted by a megatsunami in the mid-15th century. We also discuss the likely sources of this event, which happened in an isolated region of the world before the European maritime "great discoveries". This tsunami could be the source of vivid local myths that strongly suggest that a giant wave covered almost the entire island of Tongatapu at one time.
Following the 2010 VEI 4 eruption of Merapi volcano, more than 250 lahars were triggered during t... more Following the 2010 VEI 4 eruption of Merapi volcano, more than 250 lahars were triggered during two rainy seasons from October 2010 to March 2012. This high number of posteruption lahars mainly occurred in the Kali (valley) Putih watershed and was mostly associated with high-magnitude rainstorms. A lahar occurring on January 8, 2011, caused significant damage to homes in several communities, bridges, sabo dams, and agricultural crops. The aims of this contribution are to document the impacts of lahars on the Kali Putih watershed and specifically (1) to analyze the lahar frequency during the period of 1969-2012 on an inter-annual and intra-annual basis and to determine the link between the volume of tephra and the frequency of lahars; (2) to detail the lahar trajectory and channel evolution following the January 8th lahar; (3) to map the spatial distribution of the thickness and geomorphic effects of the lahar deposit; and (4) to determine the impacts of the lahar on the infrastructure (sabo dams and roads) and settlements in the distal area of the volcano. The Kali Putih watershed has experienced 62 lahars, which represent 22% of all lahars triggered on 17 rivers at Merapi between 2010 and 2012. The main geomorphic impacts are: (1) excessive sedimentation in valleys, settlements and agricultural areas; (2) undercutting of the river banks by as much as 50 m, accompanied by channel widening; and (3) abrupt changes in the river channel direction in the distal area (15-20 km downstream of the volcano). About 19 sabo dams were damaged, and 3 were totally destroyed. Over 307 houses were damaged, and the National Road Yogyakarta-Semarang was regularly cut (18 times during approximately 25 days). Although the sabo dams on Kali Putih were originally constructed to protect distal areas from lahar damage, they had little effect on the 2010-2012 rain-triggered lahars. The underlying design of those dams along this river is one of the main reasons for the major destruction in this sector of the volcano's lower slope. The catch basin capacity of the sabo dam was only 1.75 9 10 6 m 3 , whereas the total volume of the 2010-2011 lahars exceeded 5 9 10 6 m 3 . In order to prepare for future lahars, the government has invested in significant mitigation measures, ranging from structural approaches (e.g., building new sabo dams and developing an early warning system) to non-structural approaches (e.g., contingency and preparedness planning and hazard education).
astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
astarte est un programme de recherche qui vise à améliorer la résilience des populations européen... more astarte est un programme de recherche qui vise à améliorer la résilience des populations européennes aux tsunamis. Une enquête à l' échelle européenne a été conduite en 2014 -2015 dans des secteurs littoraux exposés à ce risque. Cet article en présente quelques résultats, en s'interrogeant sur le rôle que la perception récurrente, voire quotidienne, d'un paysage de mer agitée -en l' occurrence l'Océan atlantique, sur la côte portugaise de sines -peut jouer dans l'identification d'un paysage de tsunami et, dans les comportements spontanés adoptés par les usagers. Le rôle du paysage dans la perception sociale du risque a été évalué en interrogeant un échantillon d'individus -directement sur le littoral -, en les mettant en situation à l'aide de photographies de divers contextes littoraux (tsunamis, tempêtes et marée basse). il a été demandé aux populations interrogées d' évaluer le niveau de risque qu'ils percevaient sur chaque photographie. Les principales conclusions révèlent que les tsunamis appréhendés à travers des photos pendant l' enquête ont été perçus comme des situations moins risquées que celles montrant des ondes de tempêtes. ainsi, au Portugal il faudrait sensibiliser davantage les populations à l'importance des signes précurrecebido: janeiro, 2016. aceite: abril, 2017.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
HAL (Le Centre pour la Communication Scientifique Directe), 2007
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami. Eyewitnesses accounted for three main waves. The maximum height of the second wave ranged from 4.2 to 8.6 m before its breaking. Maximum flow depth after the wave's breaking reached 5 m, and maximum runup heights reached 15.7 m. Our run-up values are about 1.5 higher than those obtained by the other field surveys carried out until present. They are also higher than the values computed through preliminary models. The 17 July 2006 tsunami has been generated by a "tsunami earthquake", i.e. an earthquake of low or medium scale that triggers a tsunami of high magnitude. The run-up heights progressively decreased eastwards, which is consistent with a tsunami triggered by fault dislocation, as the one that hit the Nicaragua's coast with similar run-up heights on the 2 September 1992. An earthquake with associated landslides could also have generated the 17 July 2006 tsunami, as ever observed in Papua-New-Guinea in 1998.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reductio... more Dans le cadre du programme de recherches européen ASTARTE (Assessment, STrategy And Risk reduction for Tsunamis in Europe), une enquête a été réalisée auprès de 1500 personnes fréquentant les plages et les rivages exposés à un risque de tsunami dans huit pays européens. L'article présente une première analyse des réponses de 1139 personnes -résidents et touristes -dans les sites exposés de quatre pays méditerranéens. Deux groupes ressortent -l'un composé de touristes interrogés en Espagne et en Turquie et d'Espagnols et de Turcs, l'autre de touristes questionnés en Italie et en France, de même que d'Italiens et de Français. Ils diffèrent par leur appréhension du risque de tsunami, leur degré de connaissance des tsunamis antérieurs et des caractéristiques de tsunamis potentiels, mais aussi leur croyance en un système d'alerte. Ces différences s'expliquent par des caractéristiques démographiques, géographiques ou culturelles. L'enquête fournit des éléments essentiels à la mise en place de systèmes d'information ciblés.
Interpolation spatiale de données circulaires : application au tsunami du 26 décembre 2004
In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order... more In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order to develop hydrodynamic model, we used geo-statistical tools to reconstruct the tsunami of December, 24th, 2004 at Banda Aceh (Indonesia). On a area of 20 km2, about 1000 angles were measured, based on impact of the wave. To simplify the modelling, we assume unicity of the wave. Classical spatial statistics cannot be used in this problem since (i) kriging is not invariant by rotation; (ii) the arithmetic mean cannot be used for circular data.We first review common adaptations of kriging to circular data. Drawbacks of these methods are illustrated on our example. Finally we extend circular data theory to spatial statistics
Interpolation spatiale de données circulaires : application au tsunami du 26 décembre 2004
In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order... more In the framework of prevention, it is necessary to understand the dynamics of a tsunami. In order to develop hydrodynamic model, we used geo-statistical tools to reconstruct the tsunami of December, 24th, 2004 at Banda Aceh (Indonesia). On a area of 20 km2, about 1000 angles were measured, based on impact of the wave. To simplify the modelling, we assume unicity of the wave. Classical spatial statistics cannot be used in this problem since (i) kriging is not invariant by rotation; (ii) the arithmetic mean cannot be used for circular data.We first review common adaptations of kriging to circular data. Drawbacks of these methods are illustrated on our example. Finally we extend circular data theory to spatial statistics
Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to e... more Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to evaluate the activity of a volcano, such as Merapi volcano where associated disaster risk is regularly taking lives. Within this framework, this study aime to detect localized deformation and change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset of 2012 and one UAV-dataset of 2014. The results show that during the period 2012-2014, the crater walls are 100 m to 120 m high above the crater floor at its maximum (North to East-South-East sector), while the West and North sector presents a topographic range of 40 to 80 m. During the period 2012 – 2014, the evolution of the crater rim around the dome is generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 E+04 m3 corresponding to a maximum -9 m...
Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to e... more Spatial approach based on the deformation measurement of volcanic dome and crater rim is key to evaluate the activity of a volcano, such as Merapi volcano where associated disaster risk is regularly taking lives. Within this framework, this study aime to detect localized deformation and change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset of 2012 and one UAV-dataset of 2014. The results show that during the period 2012-2014, the crater walls are 100 m to 120 m high above the crater floor at its maximum (North to East-South-East sector), while the West and North sector presents a topographic range of 40 to 80 m. During the period 2012 – 2014, the evolution of the crater rim around the dome is generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 E+04 m3 corresponding to a maximum -9 m...
Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier i... more Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier islands are surprisingly resilient to extreme storm events. At present, little is known about barrier systems’ resilience to seismic events triggering tsunamis, co-seismic subsidence, and liquefaction. The objective of this study is, therefore, to investigate the morphological resilience of the barrier islands in responding to those secondary effects of seismic activity of the Sumatra–Andaman subduction zone and the Great Sumatran Fault system. Spatial analysis in Geographical Information Systems (GIS) was utilized to detect shoreline changes from the multi-source datasets of centennial time scale, including old topographic maps and satellite images from 1898 until 2017. Additionally, the earthquake and tsunami records and established conceptual models of storm effects to barrier systems, are corroborated to support possible forcing factors analysis. Two selected coastal sections possess ...
Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier i... more Barrier islands are indicators of coastal resilience. Previous studies have proven that barrier islands are surprisingly resilient to extreme storm events. At present, little is known about barrier systems’ resilience to seismic events triggering tsunamis, co-seismic subsidence, and liquefaction. The objective of this study is, therefore, to investigate the morphological resilience of the barrier islands in responding to those secondary effects of seismic activity of the Sumatra–Andaman subduction zone and the Great Sumatran Fault system. Spatial analysis in Geographical Information Systems (GIS) was utilized to detect shoreline changes from the multi-source datasets of centennial time scale, including old topographic maps and satellite images from 1898 until 2017. Additionally, the earthquake and tsunami records and established conceptual models of storm effects to barrier systems, are corroborated to support possible forcing factors analysis. Two selected coastal sections possess ...
The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its re... more The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its reconstruction is essentially based on legends left by oral tradition, and by archaeological evidence somehow difficult to interpret. By the fourteenth 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-15 th century, marked by an abrupt cessation of interarchipelago 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 are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring states. However, the hypothesis of a major natural disaster was never suggested up to now. 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 the Tu'i Tonga kingdom was severely impacted by a megatsunami in the mid-15th century. We also discuss the likely sources of this event, which happened in an isolated region of the world before the European maritime "great discoveries". This tsunami could be the source of vivid local myths that strongly suggest that a giant wave covered almost the entire island of Tongatapu at one time.
The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its re... more The pre-colonial history of Tonga and West Polynesia still suffers from major gaps because its reconstruction is essentially based on legends left by oral tradition, and by archaeological evidence somehow difficult to interpret. By the fourteenth 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-15 th century, marked by an abrupt cessation of interarchipelago 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 are usually assigned to internal political problems or loss of external influence vis-à-vis neighboring states. However, the hypothesis of a major natural disaster was never suggested up to now. 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 the Tu'i Tonga kingdom was severely impacted by a megatsunami in the mid-15th century. We also discuss the likely sources of this event, which happened in an isolated region of the world before the European maritime "great discoveries". This tsunami could be the source of vivid local myths that strongly suggest that a giant wave covered almost the entire island of Tongatapu at one time.
Following the 2010 VEI 4 eruption of Merapi volcano, more than 250 lahars were triggered during t... more Following the 2010 VEI 4 eruption of Merapi volcano, more than 250 lahars were triggered during two rainy seasons from October 2010 to March 2012. This high number of posteruption lahars mainly occurred in the Kali (valley) Putih watershed and was mostly associated with high-magnitude rainstorms. A lahar occurring on January 8, 2011, caused significant damage to homes in several communities, bridges, sabo dams, and agricultural crops. The aims of this contribution are to document the impacts of lahars on the Kali Putih watershed and specifically (1) to analyze the lahar frequency during the period of 1969-2012 on an inter-annual and intra-annual basis and to determine the link between the volume of tephra and the frequency of lahars; (2) to detail the lahar trajectory and channel evolution following the January 8th lahar; (3) to map the spatial distribution of the thickness and geomorphic effects of the lahar deposit; and (4) to determine the impacts of the lahar on the infrastructure (sabo dams and roads) and settlements in the distal area of the volcano. The Kali Putih watershed has experienced 62 lahars, which represent 22% of all lahars triggered on 17 rivers at Merapi between 2010 and 2012. The main geomorphic impacts are: (1) excessive sedimentation in valleys, settlements and agricultural areas; (2) undercutting of the river banks by as much as 50 m, accompanied by channel widening; and (3) abrupt changes in the river channel direction in the distal area (15-20 km downstream of the volcano). About 19 sabo dams were damaged, and 3 were totally destroyed. Over 307 houses were damaged, and the National Road Yogyakarta-Semarang was regularly cut (18 times during approximately 25 days). Although the sabo dams on Kali Putih were originally constructed to protect distal areas from lahar damage, they had little effect on the 2010-2012 rain-triggered lahars. The underlying design of those dams along this river is one of the main reasons for the major destruction in this sector of the volcano's lower slope. The catch basin capacity of the sabo dam was only 1.75 9 10 6 m 3 , whereas the total volume of the 2010-2011 lahars exceeded 5 9 10 6 m 3 . In order to prepare for future lahars, the government has invested in significant mitigation measures, ranging from structural approaches (e.g., building new sabo dams and developing an early warning system) to non-structural approaches (e.g., contingency and preparedness planning and hazard education).
The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casual... more The 17 July 2006, a tsunami struck the southern coast of Java, Indonesia, causing over 730 casualties. The triggering earthquake located 225 km off the coast of Pangandaran (9.222 • S, 107.320 • E), occurred at 15:19 LT (UTC +7) with a 7.7 magnitude on the Richter scale (Harward Center and CEA/DAM). In order to calibrate numerical models and understand the phenomenon, we conducted a 6-weeks field survey in July and August 2006 from Cimerak district in West Java to Gunung Kidul district in Central Java. Data collection involved measurements of wave height before its breaking, flow depth, run-up height, inundation depth, flow directions and a detailed chronology of the tsunami.
Previous research on debris-flow deposit structure typically reports little to no visually discer... more Previous research on debris-flow deposit structure typically reports little to no visually discernible stratigraphy. The preliminary findings presented here provide evidence for more complex internal deposit architecture with inverse grading and subunits thought to reflect individual flow surges. Ground-penetrating radar surveys, geospatial data and field observations are used to describe 10 subunits traceable over the 14 lateral radargrams imaging the lower 38 m of the deposit. Additional subunits are depicted further upslope in a longitudinal transect. As well as demonstrating the need for continued investigation of deposit architecture using non-traditional techniques, these results may help improve future interpretations of post-event deposits.
The hazardous and unpredictable nature of lahars makes them challenging to study, yet the in-flow... more The hazardous and unpredictable nature of lahars makes them challenging to study, yet the in-flow processes characterizing these events are important to understand. As a result, much of the previous research on lahar sedimentation and flow processes has been derived from experimental flows or stratigraphic surveys of post-event deposits. By comparison, little is known on the time-dependent sediment and flow dynamics of lahars in natural environments. Using video-footage of seven lahars on the flanks of Semeru Volcano (East Java, Indonesia), the present study offers new insights on the in-flow evolution of sediment in natural lahars. Video analysis revealed several distinctive patterns of sediment entrainment and deposition that varied with time-related fluctuations in flow. These patterns were used to generate a conceptual framework describing possible processes of formation for subsurface architectural features identified in an earlier lateral survey of lahar deposits on Semeru Volcano (Gomez and Lavigne, 2010a). The formation of lateral discontinuities was related to the partial erosion of transitional bank deposits followed by fresh deposition along the erosional contact. This pattern was observed over the course of several lahar events and within individual flows. Observations similarly offer potential explanations for the formation of lenticular features. Depending on flow characteristics, these features appeared to form by preferential erosion or deposition around large stationary blocks, and by deposition along channel banks during episodes of channel migration or channel constriction. Finally, conditions conducive to the deposition of fine laminated beds were observed during periods of attenuating and surging flow. These results emphasize the difficulties associated with identifying process-structure relationships solely from post-event deposit interpretation and illustrate that an improved understanding of the time-dependent sediment dynamics in lahars may be advantageous when interpreting post-event structural features.
Semeru Volcano is the highest mountain of Java (Indonesia), and a vulcanian explosion occurs ever... more Semeru Volcano is the highest mountain of Java (Indonesia), and a vulcanian explosion occurs every 15 minutes on average, since 1967. Thus a constantly renewed stock of material and the heavy monsoon rainfall [3700 mm yr −1 at 1500 m above sea level (a.s.l.)] provide a perfect setting for the study of lahars and their deposits. Hence, we examined the architecture of lahars' terraces 9·5 km from the summit in the Curah Lengkong Valley. We fi rst used ground penetrating radar (GPR) over vertical exposures of the lahars cut-bank terraces. This allowed us to better understand transversal radargrams across terraces, which are not visually accessible in the fi eld.
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