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International audience; Merapi is a two-sided, paradoxical volcano: on the one hand 1.8 million people live on its flanks. It is one of the most densely populated volcanoes on Earth, with population densities averaging 764 inhabitants per square kilometre within a 10 km radius from the summit. The main reasons for the high densities are land resources and associated livelihoods from agriculture, livestock, sand mining, and tourism. On the other hand, Merapi is also one of the world’s most active volcanoes. Dome-collapse pyroclastic density currents (PDCs) occur every few years (e.g. 1994, 2002, 2006), and more violent explosive episodes are generated with an average recurrence interval of several decades (e.g. 1872, 1930, 2010). Risk management at Merapi is based on volcanic hazard zonation (called KRB I, II, and III, from the less exposed to the most exposed), derived from its eruptive history. Since its first publication by the Volcanological Survey of Indonesia in 1978, the danger map has been updated twice, in 2002 and after the deadly eruption of Merapi in 2010. Most of the information is provided by scientists during the ‘raising awareness program’ phase and achieved in the framework of a Community-Based Disaster Risk Management (CBDRM), which empowers communities with self-developed ways of coping with crises due to natural hazards. In periods of emergency, the Center for Volcanology and Geological Hazard Mitigation provides four warning levels of volcanic activity. In 2010, Merapi produced its largest eruption since 1872, damaging around 12,000 buildings, claiming 367 lives, including 200 directly by PDCs, and triggering massive evacuations of up to 400,000 people, as counted in the evacuation camps.

International audience

International audience; Fluvial and coastal landforms are indicative of landscape river delta evolution over time and provide clues for understanding coastal adjustments to sea-level and fluvial dynamics fluctuations, tectonic displacements, and extreme waves. We have mapped the surface and sub-surface footprints of fluvial and coastal geomorphological features in the Aceh River delta, northern Sumatra, using imagery dataset, vertical facies logging and helicopter electromagnetic surveys. The result is a geomorphological map at the scale of 1:75.000 which outlines the main features of the deltaic plain, including rivers, tidal and buried channels, fluvial levees, beach ridges, swales, tidal flats and lagoons. We compare their spatial distribution to the geometry of buried sediment bodies, revealed by boreholes and resistivity maps. Buried channel belts and floodplain deposits document the former locations of the distributary channels of the Aceh River. Coastal-parallel beach ridges evidence 7–8 km of asymmetric delta progradation since the mid-Holocene sea-level high stand.

Strengthening geospatial technology is very important in order to support disaster mitigation strategy, to manage vulnerable communities and to protectcritical environments. The main challenge in identifying disaster characteristics such as mass movements is the lack of direct observation during the event because it is too dangerous for researchers. Geo-Information Technology as a product of Geographic Information Science can be used as a solution in order to model the characteristics of mass movements. The purpose of this study is focused on identifying landslide processes from point of view ofraster-based model. The method of thisresearch emphasizes dynamic landslide model derived from timeseries raster calculation using MassMov2D algorithm. The geographic database that was built for spatial modeling comes from pedogeomorphological and Remote Sensing survey outputs, especially topographic data, landforms and soil physical properties. The result shows that the relationship between pixels (neighborhood) is determined by the topology of the energy gradient line direction which allowsto transfer the value between each pixel.The movement of landslide material starts from the toe. This decreases the stability of the landslide material in the main body of the landslide and generate progressive erosion.The raster-based model can finally reconstruct and identify the stages of initiation, transport and deposition landslide material.

Studying past eruptions provides a unique opportunity to improve understanding of volcanic hazards, especially in Indonesia, where volcanic eruptions are frequently deadly and destructive. As part of a recent approach to identifying and characterizing past volcanic events, we present the first reconstruction of the eruptive history of the Ternate and Tidore Islands (North Maluku, Indonesia) for the last 22,000 years cal. BP. This interdisciplinary study (geomorphology, tephrochronology, sedimentology, geochronology, geochemistry) consists of the first stratigraphic and chronological continuum from eruptive deposits established in a set of fifteen sections in Ternate, Tidore and Maitara islands. Sedimentological and geochemical data from tephrostratigraphy studies and radiocarbon dating suggest that these islands experienced at least four major explosive events from c. 22,000 to 740 years cal. BP. The earliest event is a Plinian eruption leading to the caldera formation of Telaga volcano on the island of Tidore, c. 22,000–17,500 cal. BP. The Gamalama volcano on Ternate, whose current eruptive activity is essentially strombolian or phreatomagmatic, experienced as well a pumice eruption dated to c. 18,000 cal BP. A third event dated to c. 14,500-13,000 cal. BP, associated with a succession of abundant pyroclastic deposits of scoria, pumice, and ash, is related with the phreatomagmatic eruption at the origin of the formation of the Ngade maar on Ternate Island. Although no eruptions of Kie Matubu volcano on Tidore Island have been filled out by people since their presence in the region from the 16th century, this survey identifies two late Holocene eruptions, c. 2500 cal BP and 740 cal BP. This chronostratigraphic framework from the late Pleistocene to recent eruptions in North Maluku region provides new perspectives in managing predictive and warning information for potential eruptions that may occur on these small, vulnerable volcanic islands in the future.

International audience

International audience; Recent research suggests that major meteorite impact events into a Late Hesperian/Early Amazonian ocean likely produced a mega‐tsunami that would have resurfaced coastal areas in northwestern Arabia Terra. The orientations of the associated lobate deposits, a conspicuous type of landforms called Thumbprint Terrain, suggests that if an impact event triggered the mega‐tsunami, the most likely location of the source crater is within the northern plains regions situated north of Arabia Terra. This study focuses on the identification of impact craters that impacted into the ocean and are likely to have produced the tsunami. We selected 10 complex impact craters, based on their diameters, location, and geomorphic characteristics. Of those, the Late Hesperian ~120‐km‐diameter Lomonosov crater exhibits a unique topographic plan view asymmetry (compared to other similar‐sized and similar‐aged craters in the northern plains such as Micoud, Korolev, and Milankovic). We attribute its broad and shallow rim, in part, to an impact into a shallow ocean as well as its subsequent erosion from the collapsing transient water cavity. The likely marine formation of the Lomonosov crater, and the apparent agreement in its age with that of the Thumbprint Terrain unit (~3 Ga), strongly suggests that it was the source crater of the tsunami. These results have implications for the stability of a late northern ocean on Mars.

One of the most powerful eruptions of the Holocene, known as the Samalas eruption, had a VEI of 7 and took place on Lombok, eastern Indonesia in 1257 CE. Thick tephra fall covered the entire island, and pyroclastic density currents (PDCs) up to 50 m thick buried almost half of Lombok. Until now, there has been no detailed study of the geomorphological evolution of Lombok related to this eruption, especially for the eastern part of Lombok. The main goal of this paper is therefore to reconstruct the paleo-topography on the eastern part of Lombok before the eruption of the Samalas volcano in 1257 CE, and to analyse the subsequent landscape evolution following this eruption. Data were collected from more than 1300 points in order to gather geomorphological, geological, and geochemical information for the eastern part of Lombok over the last millennium. Data were obtained from wells (which are widespread in the studied area), natural outcrops (mainly cliffs along the shoreline and the rivers), and human-made outcrops in quarries, as well as from the two-dimensional resistivity profiling (Dipole-dipole array) carried out on eastern Lombok in 2016 and 2017. We estimate that 4435 ± 5.5 × 106 m3 of pumice-rich PDC, over a surface of 171 km2, buried the eastern part of Lombok in the aftermath of the 1257 CE eruption, and as a result of this rapid pumice-rich PDC deposition there has been some aggradation of the shoreline at some points, resulting in most of the pre-1257 coral reef being buried. After several intense rainfall events, the deposited volcanic material was probably eroded during the first decades following the 1257 CE eruption by mountain streams, producing lahars. We estimate that the remaining volume of pumice-rich PDC deposits following this erosion is 625 ± 5.5 × 106 m3 over a surface of 89 km2, which is equivalent to 14% of the initial volume.

A geomorphological survey immediately west of the Minoan town of Malia (Crete) shows that a tsunami resulting from the Bronze Age Santorini eruption reached the outskirts of the Palatial center. Sediment cores testify a unique erosional event during the Late Minoan period, followed locally by a high energy sand unit comprising marine fauna. This confirms that a tsunami impacted northern Crete and caused an inundation up to 400 m inland at Malia. We obtained a radiocarbon range of 1744–1544 BCE for the secure pre-tsunami context and an interval 1509–1430 BCE for the post-event layer. Examination of tsunami deposits was used to constrain run-up not exceeding 8 m asl. The results open the field for new research on the Bronze Age Santorini tsunami regarding both impact and consequences for the Minoan civilization.

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- 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 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.

K-Pass FM Radio Katapang is one of the radios disseminating information about disasters that focuses on training, awareness, and understanding of the people of Katapang Regency to play a role in dealing with disasters and help reduce disaster risk as well. This study aimed to determine the dissemination pattern of disaster information based on community radio conducted by Radio K-Pass FM Katapang. The research used a qualitative approach through case studies research methods. Data collection techniques included in-depth interviews, observation, documentation, and literature studies. Informants amount six people consist of resource persons consisting of community radio administrators, people who feel the impact of the existence of community radio, and people who take part in community radio programs. The study results showed that the dissemination of disaster information on Radio K-Pass FM Katapang increased the awareness of the local community about the dangers of disasters. The disaster information on K-Pass FM Radio Katapang went through three stages: the pattern of dissemination of disaster mitigation information (pre), the pattern of disseminating information when the disaster occurred (in), and post-disaster information (past). This community radio also established a Rescue School that aims to provide knowledge and actions that the community can carry out when a disaster occurs. This study concludes that Radio K-Pass FM Katapang has succeeded in becoming a community radio that positively impacts society, especially in disseminating information related to disasters. Therefore, Radio K-Pass FM Katapang still exists today even though it has been around for a long.

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&rsquo, 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&ndash, 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 different geomorphic settings are investigated: (1) Lambadeuk, the coast overlying the Sumatran Fault system, (2) Kuala Gigieng, located in between two segments of the Sumatran Fault System. Seven consecutive pairs of comparable old topographic maps and satellite images reveal remarkable morphological changes in the form of breaching, landward migrating, sinking, and complete disappearing in different periods of observation. While semi-protected embayed Lambadeuk is not resilient to repeated co-seismic land subsidence, the wave-dominated Kuala Gigieng coast is not resilient to the combination of tsunami and liquefaction events. The mega-tsunami triggered by the 2004 earthquake led to irreversible changes in the barrier islands on both coasts.

This paper offers a reflection on the constraints imposed by the focus of the management of the pandemic at the global level and of the epidemic at the level of the territories on the preparation and anticipation of new threats, such as natural hazards., Cet article propose une réflexion sur les contraintes que fait peser la focalisation de la gestion de la pandémie au niveau mondial et de l’épidémie au niveau des territoires sur la préparation et l’anticipation de nouvelles menaces, tels que des aléas naturels.

The economic downturn at the start of the 21st Century combined with the rise of new economies have helped propelling the need for cheaper, rapid and yet accurate data acquisition methods, including point-cloud producing technologies. As population is ageing in countries like Japan or Taiwan, and as climate change is bound to increase the frequency and number of landslides (at least until sediment stocks are depleted), the need of rapid and low-manpower data acquisition and processing has become increasingly essential. It is within this framework that the present contribution aims (1) to present research on present technologies for landslide monitoring, as well as emerging systems, and (2) to propose “new” ideas for point-cloud processing and data usage without having to grid or interpolate data. The authors thus use a variety of field locations around the pacific and in France using as a method ALS (Airborne Laser Scanning), TLS (Terrestrial Laser Scanning) and SfM-MVS (Structure from Motion—Multiple View Stereophotogrammetry). Then the authors present recent advances in landslide monitoring technology with the YellowScan UAV-ALS. As the resulting mounting amount of data presents constrains to the data processing steps, the authors also present ideas to progress processing: (1) developing a point-cloud signature to avoid gridding, and (2) a conceptual algorithm to process the point-clouds as vectors between a machine and a reflective object, recording the free space and the objects. In this way catastrophic landslides can be characterized from the signature of the data and the distribution of fill and voids without going through the traditional analysis on a Cartesian grid. The authors have worked on those techniques to provide fast and accurate data for landslides hazards and disaster risk.

Tidore and Hiri Islands in North Maluku Province is the result of a complex tectonic setting. In contrast with Ternate Island and its well-known volcano, Gamalama volcano, there is still a lack of research about volcanic information or volcanic landform in Tidore and Hiri Islands. Even though the two islands also have volcanoes, i.e., Hiri and Tidore/Kiematubu volcano. This study aims to provide geomorphological information, especially in Tidore and Hiri Islands, since this information is hard to find whereas it is very important to disaster mitigation and landuse planning. We used remote sensing images, digital elevation models (DEM), and geological maps to classify geomorphological information of the small island of Tidore and Hiri in the North Maluku based on geomorphological aspects, i.e., morphology, morphogenesis, morpho-chronology, and morpho-arrangement. As a volcanic island, the slope in Tidore and Hiri Island is dominated by a slightly steep (8°-16°) and a steep slope (16°-35°), while the relief is dominated by hills and mountainous. Volcanic landforms on Tidore and Hiri Islands are characterized by relatively symmetrical cone-shaped volcanic cones, which are accumulations of falling pyroclastic material and lava ejected from magma vents. Volcanic islands include the case of Tidore and Hiri Island have radial centrifugal river flow patterns. The material on Tidore and Hiri Islands is dominated by Holocene volcanic rocks. In Tidore, there is alluvial material on the west and east coasts of the island. This study result also can be developed into more detailed geomorphological maps, or landscape evolution in a volcanic island, or spatial planning.

Kiematubu volcano is often considered as non-volcanic, even though it consists of basalt material, since it has never erupted before. In fact, that small volcanic islands have a high risk due to their restriction on means and resources. The study aims to assess the social vulnerability of the community in Tidore Island that may be exposed to the eruption of the Kiematubu volcano. There has not been previous research in Tidore Island regarding volcanic vulnerability yet. The social vulnerability is an initial assessment of disaster management, which will affect in optimizing community’s capacity then minimizing the disaster impacts. Social parameter of demographic condition, health facilities, and education facilities was weighted to assess social vulnerability. The result shows that the social vulnerability class of Tidore Island is dominantly low, approximately 80%, the rest is middle and high, with a percentage of 13% and 7%, respectively. Mostly, the low vulnerable villages are due to less population density. However, the highly vulnerable villages, Gamtufkange and Indonesiana, consist of very high and high population density. The southeast part of Tidore Island, where both villages are situated, is the center of human activities, such as governmental, trades, and education.

International audience; Most tsunamis occur after large submarine earthquakes, particularly in the Pacific Ocean. However, following the 2004 tsunami in the Indian Ocean, tsunami hazard awareness was significantly raised at the global scale, and warning systems were developed in many other regions, where large tsunamis are rarer but can also produce large catastrophes. Here we first review the basic physics of a tsunami, from its triggering to its coastal impact, and we offer a review of the geophysical and sea-level data that can describe the various processes operating during a tsunami. Global Navigation Satellite System (GNSS) data have a key role in better describing the ground deformation following a tsunamigenic earthquake close to the coast. The GNSS observations complement seismological data to constrain the rupture model rapidly and robustly. Interferometric Synthetic Aperture Radar (SAR) also contributes to this field, as well as optical imagery, relevant to monitoring elevation changes following subaerial landslides. The observation of the sea-level variations, in the near field and during the propagation across the ocean, can also increasingly benefit from GNSS data (from GNSS buoys) and from robust satellite communication: pressure gauges anchored on the seafloor in the deep ocean contribute to warning systems only by data continuously transmitted through satellites. The sounding of ionospheric Total Electron Content (TEC) variations through GNSS, altimetry, or a ground-based airglow camera, is a promising way to record tsunami initiation and propagation indirectly. Finally, GNSS, optical and SAR imagery are essential to map and quantify the damage following tsunami flooding. Satellite data are expected to contribute more to operational systems in the future provided they are reliably available and analysed in real time.

International audience

L’élevage rend de nombreux services dans les territoires dans lesquels il est implanté et il est intéressant de pouvoir les appréhender dans leur globalité. L’objectif de cette étude est de réaliser une qualification du bouquet de services rendus par les systèmes de production de foie gras agroforestiers en prenant comme exemple l’association oies / noyers en Périgord. Le cadre conceptuel utilisé a été adapté de Ryschawy et al (2015). Les données proviennent 1) de mesures biologiques (croissance des arbres ou production de fruit, comportement des animaux, biodiversité) ou pédologiques (fertilité des sols) réalisées sur des oies adultes élevées sur des parcours contenant des noyers âgés de 7 à 11 ans et 2) des données de la littérature pour les autres dimensions. Notre analyse montre que l’élevage des oies pour la production de foie gras sur des parcours implantés de noyers est à bénéfices réciproques puisque l’ombre apportée par les noyers est très appréciée des animaux, et que les déjections des oies fertilisent les arbres ce qui augmente leur croissance et leur production de fruits sans altérer leur qualité sanitaire. Cette association rend des services i) d’approvisionnement par la fourniture en quantité relative modérée de foie gras, de viande d’oie, de bois de noyers, de noix et de coproduits (duvets et graisse d’oie, coques et brou de noix) ; ii) de préservation de la qualité environnementale en valorisants des coproduits dans l’alimentation des animaux (77 t/an) et en préservant la fertilité du sol ; iii) patrimoniaux et de qualité de vie par le biais de produits labellisés et à haute valeur ajoutée (AOC Noix du Périgord, marque Oie du Périgord) et le maintien du patrimoine culturel et gastronomique; et iv) de vitalité territoriale par la création d’emplois et la contribution à l’agrotourisme. Il a aussi des externalités négatives (impacts environnementaux, acceptabilité sociale du gavage et risques sanitaires). Ce travail permet de montrer que les bénéfices de l’association oies/noyers sont beaucoup plus larges que les intérêts techniques et économiques qui les ont justifiés.

Semeru Volcano is an active stratovolcano located in East Java (Indonesia), where historic lava flows, occasional pyroclastic flows and vulcanian explosions (on average every 5 min to 15 min) generate a stock of material that is remobilized by lahars, mostly occurring during the rainy season between October and March. Every year, several lahars flow down the Curah Lengkong Valley on the South-east flank of the volcano, where numerous lahar studies have been conducted. In the present contribution, the objective was to study the spatial distribution of boulder-size clasts and try to understand how this distribution relates to the valley morphology and to the dynamic and deposition dynamic of lahars. To achieve this objective, the method relies on a combination of (1) aerial photogrammetry-derived geospatial data on boulders' distribution, (2) ground penetrating radar data collected along a 2 km series of transects and (3) a CFD model of flow to analyse the results from the deposits. Results show that

This article presents the characteristics of the small islands of Tidore and Hiri, which are vulnerable to the dangers of volcanic eruptions in Indonesia. The physical condition of the area is very important for carrying out a sustainable disaster risk reduction analysis; therefore, climate and topographic data are important to know. The limited availability of data in the study area causes climate data to be obtained from NASA’s Earth Science Data Systems (ESDS) and regional topographical presentation of Indonesia’s national DEM data. The results show that in the period 2004 to 2014, the temperature in the study area ranged from 292 K to 309 K. The islands of Tidore and Hiri have monthly precipitation between 50 mm to 500 mm.

The debris avalanche deposit (DAD) coverage can drastically modify the surrounding landscape of volcanoes. DAD can be distinguished by hummocky irregular surface, jigsaw fissure, and mixing horse-shoe shape. Due to its particular shape of a hummock, the topography can be easily identified using DEM (Digital Elevation Model) and satellite imagery. The aim of this study is to characterize hummocky terrain in Lombok Island, which is located in the Kalibabak formation on the Geological map through the geomorphic approach. Hummocky terrain in this study are analyzed using DEM data from DEMNAS (DEM Nasional: 0.27-arcsecond resolution). Our study of this DAD encompasses seven variables, namely H/L ratio, numbers hummocks, distance to source, slope, area (size), relative height, topographic section, and hummock-spreading shape. A minimum of 756 hills derived from this DEM are considered as hummocks from this DAD, which extends ~18 km (NS) and ~25 km (WE) in the central part of Lombok Island. With an area of ~200 km2 and a volume estimated around 8.8 km3, the Kalibabak DAD is more than three times larger than the one of the Mount St-Helens in 1980. The morphology of hummocky terrain is bounded by a sudden change of slope, which is indicated by a river confluence. Average hummock size is 2.7 ha and average distance between each hummock is 150 m to 300 m. The hummocks are characterized by steep slopes (25 % to 45 %) at the boundary to colluvium plain (debris deposit), which makes them easy to identify using DEM. Hummocks spreading distribution forms a conical-like shape with a H/L ratio of 0.13. The spreading distribution shape, the H/L and V/L ratios are useful as an input for reconstructing the mechanism of debris avalanche emplacement.

As one of the most powerful volcanic events of the Holocene era with a Volcanic Explosivity Index of seven, the 1257 CE eruption of Samalas volcano in the Rinjani Volcanic Complex had large consequences for Lombok Island (Indonesia) and its surrounding area. This huge eruption with an enormous volume of ejected material (4435 ± 5.5 × 106 m3), was recorded in local written sources, called Babad, that were compiled around the sixteenth century and contain oral stories and myths. In this study, we present two written sources, namely Babad Lombok and Babad Suwung, which undoubtedly refer to the 1257 CE ultraplinian eruption of Samalas volcano. In addition to detailed analysis of the volcanic deposits, interviews with old Javanese linguists and museum employees were carried out to clarify the meanings of some words as well as the genesis of the Babads. The results from field observation and interviews were analyzed and compared with previous research. Babad Lombok describes the process of the Samalas eruption, the formation of the Segara Anak caldera, and the impacts of the voluminous ash fall and pyroclastic flows on Lombok Island. Meanwhile, Babad Suwung describes the impacts of the 1257 CE volcanic eruption on Talkuwang (Taliwang), on the western coast of Sumbawa Island. This description encompasses several volcanic processes including fallout and pyroclastic surges. The exegesis of Babad Lombok and Babad Suwung could be the oldest observations of a caldera-forming eruption in Southeast Asia. They also document the oldest pyroclastic surges in the world after those of Vesuvius as described by Pliny the Younger in 79 CE.

International audience