Publications of Aurelia Hubert
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See detailDiscrete element modeling of a subduction zone with a seafloor irregularity and its impact on the seismic cycle
Jiao, Liqing; Chan, Chung-Han; Scholtes, Luc et al

in Solid Earth (2020)

Seafloor irregularities influence rupture behavior along the subducting slab and in the overriding plate, thus affecting earthquake cycles. Whether seafloor irregularities increase the likelihood of large ... [more ▼]

Seafloor irregularities influence rupture behavior along the subducting slab and in the overriding plate, thus affecting earthquake cycles. Whether seafloor irregularities increase the likelihood of large earthquakes in a subduction zone remains contested, partially due to focus put either on fault development or on rupture pattern. Here, we simulate a subducting slab with a seafloor irregularity and the resulting deformation pattern of the overriding plate using the discrete element method. Our simulations illustrate the rupture along three major fault systems: megathrust, splay and backthrust faults. Our results show different rupture dimensions of earthquake events varying from tens to ca. 140 km. Our results suggest that the recurrence interval of megathrust events with rupture length of ca. 100 km is ca. 140 years, which is overall comparable to the paleoseismic records at the Mentawai area of the Sumatran zone. We further propose the coseismic slip amounts decrease and interseismic slip amounts increase from the surface downwards gradually. We conclude that the presence of seafloor irregularities significantly affects rupture events along the slab as well as fault patterns in the overriding plate. [less ▲]

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See detailA 3800 yr paleoseismic record (Lake Hazar sediments, eastern Turkey): Implications for the East Anatolian Fault seismic cycle
Hubert, Aurelia ULiege; Lamair, Laura ULiege; Hage, Sophie et al

in Earth and Planetary Science Letters (2020), 538

The East Anatolian Fault (EAF) in Turkey is a major active left-lateral strike-slip fault that was seismically active during the 19th century but mostly quiet during the 20th century. Geodetic data ... [more ▼]

The East Anatolian Fault (EAF) in Turkey is a major active left-lateral strike-slip fault that was seismically active during the 19th century but mostly quiet during the 20th century. Geodetic data suggests that the fault is creeping along its central part. Here we focus on its seismic history as recorded in the sediments of Lake Hazar in the central part of the EAF. Sediment cores were studied using X-ray imagery, magnetic susceptibility, grain-size, loss-on-ignition and X-ray fluorescence measurements. Recurring thin, coarse-grained sediment units identified as turbidites in all cores were deposited synchronously at two deep study sites. The turbidite ages are inferred combining radiocarbon and radionuclide (137Cs and 210Pb) dating in an Oxcal model. A mean recurrence interval of ~190 years is obtained over 3800 yrs. Ages of the recent turbidites correspond to historical earthquakes reported to have occurred along the EAF Zone or to paleoruptures documented in trenches just northeast of Lake Hazar. The turbidites are inferred to be earthquake-triggered. Our record demonstrates that Lake Hazar has been repeatedly subjected to significant seismic shaking over the past 3800 years. The seismic sources are variable: ~65% of all turbidites are associated with an EAF source. The seismic cycle of central EAF is thus only partly impacted by creep. [less ▲]

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See detailSharp changes in lake-levels preconditioning seismogenic mass failures in the Dead Sea
Lu, Yin; Agnon, Arnotz; Marco, Shmuel et al

in 22nd EGU General Assembly, held online 4-8 May, 2020, id.14056 (2020)

Subaqueous mass failures that comprise slides, slumps and debris flows are a major process that transport sediments from the continental shelf and upper slope to the deep basins (both oceans and ... [more ▼]

Subaqueous mass failures that comprise slides, slumps and debris flows are a major process that transport sediments from the continental shelf and upper slope to the deep basins (both oceans and lacustrine settings). They are often viewed together with other natural hazards such as earthquakes, and can have serious socioeconomic consequences. It is increasingly important to understand the relationship between mass failures and climate-driven factors such as changes in water-level. Despite extensive marine investigations on this topic world-wide, the relationship between changes in water-level and mass failures is still highly disputed. This is due largely to the significant uncertainties in age dating and different potential triggers and preconditioning factors of mass failure events from different geological settings. Here, we present a 70 kyr-long record of mass failure from the Dead Sea Basin center (ICDP Core 5017-1). This sedimentary sequence has been dated in high accuracy (±0.6 kyr) and has similar responses to climate forcing. Moreover, the mass failure record is interpreted to be controlled by a single trigger mechanism (i.e. seismicity).Based on the recent detailed study on the sedimentological signature of seismic shaking in the Dead Sea center, these seismogenic mass failures (seismites) account only for a part of the whole seismites catalog, suggesting that mass failure follows only part of seismic shaking irrespective of intensities of the shaking. This is evidenced by the common absence of mass failures following the in situ developed and preserved seismites (e.g., the in situ folded layer and intraclast breccias layer) which represent different intensities of seismic shaking. This feature implies that some non-seismic factor(s) must have preconditioned for the seismogenic mass failures in the Dead Sea center.Our observations reveal decoupling between change in sedimentation rates and occurrence probability of these seismogenic mass failures, thus suggesting that a change in sedimentation rate is not the preconditioning factor for the failure events. While 79% of seismogenic mass failure events occurred during lake-level rise/drop in contrast to 21% events occurred in the quiescent intervals between. Our dataset implies that seismogenic mass failures can occur at any lake-level state, but are more likely to occur during lake-level rise/drop due to the instability of the basin margins. In addition, the seismogenic mass failures occurred more frequently during glacials (characterized by highstand and high-amplitude lake-level changes) than during interglacials, as a result of the morphologic characteristics of the lake margin slopes and different lithologies (e.g. halite) influences which are both connected to the glacial-interglacial lake-level changes. [less ▲]

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See detailOrganic carbon accumulation and productivity over the past 130 years in Lake Kawaguchi (central Japan) reconstructed using organic geochemical proxies
Yamamoto, Shinya; Hubert, Aurelia ULiege; Lamair, Laura et al

in Journal of Paleolimnology (2020), 64

Organic matter in lake sediments contains information that can be used to reconstruct lake environmental histories over decades or centuries. In this study, we used organic geochemical proxies (i.e ... [more ▼]

Organic matter in lake sediments contains information that can be used to reconstruct lake environmental histories over decades or centuries. In this study, we used organic geochemical proxies (i.e., total organic carbon [TOC], TOC/total nitrogen [TN] atomic ratios [C/N], stable carbon isotope ratios of TOC [d13CTOC] and palmitic acid [d13CC16:0], and nitrogen isotope ratios of bulk sediment [d15Nbulk]) in sediments from Lake Kawaguchi, Japan, to reconstruct detailed histories of the organic matter accumulation and lake productivity over the past 130 years. Vertical profiles of the mass accumulation rate (MAR) of TOC in the eastern lake basin (core KAW14-7A) showed parallel increases with the C/N ratio from the 1960s to the 1980s, indicating an accelerated delivery of terrestrial organic matter via anthropogenic land-use change. In contrast, the C/N ratios in the western and central basins (cores KAW14-1A and KAW14-4B, respectively) were almost constant prior to the 1980s, suggesting that the increasing trends in the TOC MAR values in these cores are most likely attributable to the onset of eutrophication associated with rapid economic growth after the mid-1950s. On the other hand, the d15Nbulkshowed a gradual increase from the late 1870s, providing evidence for anthropogenic nitrogen input to the lake prior to the apparent eutrophication. After the 1960s–1970s, the d15Nbulk values rapidly increased, demonstrating water deterioration associated with the direct nutrient discharge into the lake from domestic wastewater. The d13CC16:0 profiles displayed similar increasing trends to d15Nbulk from the mid-1960s, demonstrating a close relationship between lake productivity and anthropogenic nitrogen input in Lake Kawaguchi. Our geochemical records as a whole clearly show high algal productivity and enhanced deposition of organic matter in recent decades, suggesting that the amelioration of the lake water is a likely consequence of the transfer of nnutrients to the sediment by enhanced productivity, rather than a decrease in the amount of nutrient inflow into the lake. [less ▲]

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See detailEntre pressions anthropiques et marines, l’érosion côtière autour de la ville de Kribi, Cameroun
Mbevo Fendoung, Philippes ULiege; Hubert, Aurelia ULiege

Conference (2019, September 20)

Dans sa vision à l’horizon 2035, le gouvernement camerounais entend construire son économie au rang des économies intermédiaires. Pour ce faire, il se concentre sur la construction d’infrastructures ... [more ▼]

Dans sa vision à l’horizon 2035, le gouvernement camerounais entend construire son économie au rang des économies intermédiaires. Pour ce faire, il se concentre sur la construction d’infrastructures majeures et Kribi joue un rôle central dans cette initiative avec notamment l’autoroute Kribi-Edéa et le port en eau profonde de Kribi. Comme pour toute structure de port maritime, la construction du port de Kribi en 2015 a eu un impact important sur le littoral et a entraîné une érosion côtière importante. La digue de protection du port a été construite sur la trajectoire de la dérive côtière, ce qui crée des situations d’aggradation en aval mais d’érosion côtière en amont. En outre, le développement de Kribi a donné lieu à l’extension des plantations agro-industrielles de SOCAPALM et HEVECAM. Tout cela contribue à l’affaiblissement de l’environnement côtier à la fragilité de son écologie. Une étude antérieure de Tchindjang et al. (2019) a déjà montré qu’il y avait des changements côtiers importants au Cameroun. Ils se produisent principalement à l’embouchure des grandes rivières (Lobé, Nyong et Ntem), mais aussi à des endroits où l’amplitude des marées et la vitesse des vagues sont importantes. Globalement, les zones de couverture côtière avancée entre 1973 et 2007 ont une superficie moyenne de 4 081 400 m2 représentant 45 % de la dynamique totale. En revanche, il existe une dynamique régressive correspondant au retrait linéaire côtier qui affecte principalement les secteurs concaves de la côte, composés principalement de roches ou de sédiments meubles. Entre 1973 et 2007, il s’agissait d’une surface moyenne de 4 949 550 m2 représentant 55 % de la dynamique totale. Le recul des côtes peut être amplifié et accéléré par les activités humaines, tout en constituant une menace pour les investissements et les constructions localisées sur le littoral et pour la biodiversité in situ, en dépit des travaux de protection qui peuvent y être construits. Le but de cette recherche est d’analyser la dynamique de la côte kribienne entre 2000 et 2019, de mettre en évidence les facteurs amplificateurs et de quantifier les zones d’accumulation et de recul des zones côtières. L’approche méthodologique articule deux approches: (i) une analyse par télédétection visant à étudier la dynamique de l’utilisation des sols et du littoral entre 2000 et 2019, à l’aide d’images satellite de type Lansdat et sentinelle. Les images ont une résolution spatiale qui varie de 10 à 15 m. Une analyse statistique de l’évolution de la démographie et des surfaces imperméabilisées. (ii) L’outil Digital Shorline Analysis System (DSAS) est utilisé pour modéliser la cinématique côtière. Comme prévu, le niveau de régression du littoral sera connu, ainsi que l’état de l’occupation du sol et ses implications sur la dynamique côtière. [less ▲]

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See detailAPPLICATION OF REMOTE SENSING AND GIS IN COASTAL EROSION MAPPING IN CAPE CAMEROON
Mbevo Fendoung, Philippes ULiege; Tchindjang, Mesmin; Hubert, Aurelia ULiege

Conference (2019, July 03)

Cape Cameroon is a small, insular territory bordering the northern shore of the Wouri estuary in Cameroon. It is located in the 6th district of the city of Douala (1 907 479 inhabitants (BUCREP, 2010 ... [more ▼]

Cape Cameroon is a small, insular territory bordering the northern shore of the Wouri estuary in Cameroon. It is located in the 6th district of the city of Douala (1 907 479 inhabitants (BUCREP, 2010)), with Manoka as its capital. It is occupied by 2654 inhabitants. This territory is occupied mainly by a Nigerian ethnic group, and the Cameroonian sovereignty has been fighting in this Cameroonian territory since the 1998-2008 conflict with Nigeria on the Bakassi peninsula.Coastal erosion is very intense and affects populations and ecosystems. Sustainable development is a particular challenge in this insular territory because the population is confronted with important coastal erosion phenomena and that cannot migrate inland because of the Mabé swamp Natural Reserve. Since the beginning of the 2000s, coastal erosion has removed houses, infrastructures and a large part of the Mabé Reserve. This contribution aims to mobilize remote sensing and GIS tools and data to (1) map the different sequences of the coastline retreat in Cape Cameroon and highlight the main factors, and (2) map the mangrove degradation due to the inland motion of the anthropic pressure, and (3) make projection for future of this territory. For modeling the coastal kinematics, the mapping is based on the Digital Shoreline Analysis System (DSAS) model, developed by Thieler et al. (2009). We used supervised classifications of Landsat images from the 1975, 1986, 2000 and 2018 with 30-meter resolution according to the maximum likelihood algorithm. We could thus assess the land use change and extract shorelines. Furthermore we use field observations, the testimonies of the people who lived for a long time along the shore to access if (1) erosion occurs continuously or during extreme events and if (2) mangrove degradation is linked to coastal erosion. Between 1986 and 2014, earth losses are estimated at more than 103 ha. Mangroves recorded a considerable degradation that the rate is estimate of 13.68%. The improved quantification of coastal erosion (in terms of soil area loss), the human occupation and land degradation through time and its possible future evolution allow to address the specific challenge of closed restricted territories occupied by growing poor and marginalized population, and the long-term sustainability of a natural reserve in such environment. [less ▲]

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See detailCosmogenic data about uplifted river terraces: implications regarding the central north anatolian fault segment and the central pontide orogenic wedge
Hubert, Aurelia ULiege; Drab, Laureen; Benedetti, Lucilla et al

Conference (2019, January 29)

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See detailQuestion about the seismic cycle of the East Anatolian Fault and its seismic versus aseismic behavior
Hubert, Aurelia ULiege; Lamair, Laura ULiege; Hage, Sophie et al

Conference (2019, January 29)

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See detailCOMBINING GEOLOGY, GEOMORPHOLOGY AND GEOTECHNICAL DATA FOR A SAFER URBAN EXTENSION: APPLICATION TO THE ANTANANARIVO CAPITAL CITY (MADAGASCAR)
ANDRIAMAMONJISOA, Solofo Nirina; Hubert, Aurelia ULiege

in Journal of African Earth Sciences (2019)

Metropolitan and suburban areas in Africa are rapidly expanding with, in general, a poor safe urban management. Urban development in zones not suitable for construction leads to significant economic loss ... [more ▼]

Metropolitan and suburban areas in Africa are rapidly expanding with, in general, a poor safe urban management. Urban development in zones not suitable for construction leads to significant economic loss. The aggregate building damage combined with other environmental treats like drought, flooding or landsliding are enhancing African city vulnerability. Simple cartographic products made available to the general public could facilitate the first stage of planning and management considering parameters that affect building foundation. We combine here in ARCGIS geological, geomorphological and geotechnical data to provide such a framework focusing on the capital city of Antananarivo in Madagascar. The city was initially constructed on basement hills covered with a thick loose weathered layer and is expanding into the alluvial lowland watered by the Ikopa River. About 221 boreholes with pressumeters and laboratory data provide a picture of the underground characteristics, and allow the computation of the soil bearing capacity, the key parameter we used to assess building suitability. Lithology, slope, land-use and ground water level are combine to build a first geotechnical map that is completed using a mapping of the soil bearing capacity combined with land-use and geohydrological constraints. The geotechnical maps divide the city into zones with different constructive conditions that can be use as a first tool for urban development planning. [less ▲]

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See detailTypologies, processus et stratigraphie des contourites dans le Rift de Corinthe - Approche intégrée terrain, sismique et données océanographiques.
Rubi, Romain ULiege; Rohais, Sébastien; Hubert, Aurelia ULiege

Conference (2019)

Les dépôts sédimentaires associés aux phases de rifts sont contrôlés par le contexte géodynamique et les failles normales. Lors de l’initiation du rift, les dépôts sont continentaux et généralement formés ... [more ▼]

Les dépôts sédimentaires associés aux phases de rifts sont contrôlés par le contexte géodynamique et les failles normales. Lors de l’initiation du rift, les dépôts sont continentaux et généralement formés par des réseaux fluviaux débouchant dans des lacs isolés. Dans une deuxième phase, ces sous-bassins se connectent et s’approfondissent laissant place à une sédimentation clastique lacustre ou marine. Parallèlement à ces processus gravitaires de dépôts, les sédiments peuvent être remaniés par des processus indépendants de la source sédimentaire, pendant ou après le dépôt, par des courants de fond. Bien que le Rift de Corinthe ait été largement étudié, les modèles tectono-sédimentaires existants sont basés sur une sédimentation gravitaire, et ne considèrent pas ces processus de remaniement. Une approche intégrée basée sur de nouvelles données sédimentologiques, sismiques et océanographiques, d’affleurements et de carottes, permet d’illustrer la formation d’un système sédimentaire mixte turbiditique et contouritique modifiant significativement les modèles tectono-sédimentaires utilisés. L’étude de terrain couplée au modèle photogrammétrique à haute-résolution des affleurements localisés sur la marge sud du Rift de Corinthe permet de documenter les facies, les associations de facies ainsi que l’architecture d’un système pro-deltaïque. Ce prodelta est formé par deux moats actifs et parallèles limités par un drift commun. Ces moats forment un angle de 70 à 90° avec l’axe de progradation du delta, et s’écoulent parallèlement à la côte. Le drift est formé indépendamment du remplissage des moats par deux types de séquence : une séquence turbiditique et une séquence bigradationnelle contouritique. Les moats sont remplis par des facies de sables et de conglomérats à imbrication transverse, indiquant un remaniement persistant des clastes par des courants perpendiculaires à la zone d’apport et donc un export du matériel grossier dans la partie distale du bassin sous l’action de courants de fond. Les données de sismique illustrent une architecture comparable au niveau des deltas actuels du Golfe de Corinthe. De plus, la pente Nord du Golfe présente également des sediment-waves, des moats perchés et des plastered drifts. Ces moats sont érosifs, migrent à contre-pente et sont limités vers le bassin par un drift. Ces corps morphosédimentaires formés par le remaniement et l’érosion des sédiments témoignent de la présence de courants parallèles à la côte. La cartographie de l’ensemble de ces corps à l’échelle du Golfe et l’analyse des cartes d’isopaques, durant les derniers 600 ka a permis de mieux contraindre les processus sédimentaires dominants au cours de l’évolution du Rift. Ces processus de haute énergie modifient le cheminement sédimentaire et impliquent certaines configurations paléoocéanographiques et paléogéographiques qui sont cruciales dans l’évolution du Rift et notamment sa connexion avec la Méditerranée. Actuellement le Golfe de Corinthe est en connexion avec la Méditerranée à l’Ouest au niveau du détroit de Rion. Ce niveau de seuil, d’une bathymétrie actuelle de 62 m, contrôle le caractère lacustre ou marin du Golfe en fonction de l’eustatisme. Cette zone est donc cruciale dans la compréhension de la dynamique océanique du Golfe. C’est pourquoi, une campagne sismique et océanographique, a été réalisée en partenariat avec l’Université de Patras en Juin 2019. Elle a permis d’imager (Multibeam, Chirp, Sparker, Camera) et de mesurer pour la première fois des courants de fond (ADCP). Les résultats préliminaires documentent les facies et les géométries sédimentaires associées à une circulation de courants de l’ordre de 1 m/s ainsi que de nombreuses surfaces d’érosion sous-marines en période de haut niveau marin. Ces surfaces d’érosion associées à un contexte transgressif sont à intégrer aux interprétations stratigraphiques classiques jusqu’alors proposées. [less ▲]

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See detailWeathering pattern of Messinian lithothamnium limestones: implication about paleoclimatic conditions
Moulana, Meriem Lina ULiege; El Ouahabi, Meriam ULiege; Boulvain, Frédéric ULiege et al

in Geologica Belgica (2019)

Limestones are prevalent in Algeria. These formations since their deposition have been affected by a range of weathering, dissolution and recrystallization processes dependant of the paleoclimatic ... [more ▼]

Limestones are prevalent in Algeria. These formations since their deposition have been affected by a range of weathering, dissolution and recrystallization processes dependant of the paleoclimatic conditions they sustained. These transformations also affect the potential hazard that these karstic terrains represent. We focus here on the Boukadir Region situated at the foot of the Ouarsenis Mountain (Fig. 1). The region comprises the Ouarsenis northern piedmont composed of ~15o north dipping lithothamnium limestones of the Messinian period that rest unconformably upon blue marls of the upper Miocene, and to the south the E-W striking lower Chlef Basin filled by Plio-Quaternary sediments and flooded by the Chlef River. The lithothamnium carbonates rocks form a major deep aquifer in the Basin. The Basin is crossed along its southern edge by the Relizane strike-slip fault. In June 1988, there was a large collapse sinkhole of 60 m in diameter and 35 m of deep that occurred along the national road RN4 near the southern edge of the basin (LCTP, 1989). Drilling shows that sinkhole can be associated to lithothamnium limestones that were covered by more than 61 m of sediments at that location. No other sinkhole formed since this accident. In this study we investigate the weathering pattern of the lithothamnium limestones to unravel the likelihood of formation of large sinkholes in this formation. Boreholes and quarries show that the Messinian Calcareous limestones of the Boukadir region are deeply weathered and partly recrystallized calcareous rocks; the weathering affects its entire thickness reaching a maximum of 200 m. This weathering pattern is not visible a few kilometres more to the east, in limestones having a similar origin. To unravel the specific paleoclimatic conditions that these limestones sustained, we combine field work and on selected samples, petrographic thin section and mineralogical (XRD) analysis and SEM observations. Field work in quarries and in the wadi shows that the lithothamnium limestones are composed of altering sandstone rich beds with a calcareous cement and bioconstructions rich beds. .. [less ▲]

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See detailTracking magma movements in the Virunga volcanic province using seismic Amplitude Ratio Analysis (SARA)
Subira, Josué; Caudron, Corentin; Hubert, Aurelia ULiege et al

in Geologica Belgica (2019)

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See detailSedimentary evolution of the Sagara coastal area in Japan and its potential to preserve extreme wave deposits
Kempf, Philipp; Garrett, Ed; Fujuwara, Osamu et al

in Geologica Belgica (2019)

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See detailUse of high-resolution seismic reflection data in the paleogeographical reconstruction of shallow Lake Yamanaka (Fuji Five Lakes, Japan)
Lamair, Laura ULiege; Hubert, Aurelia ULiege; Yamamoto, S. et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2019), 514

High-resolution seismic profiles, combined with the integration of published drilling data, provide a detailed paleoenvironmental history of Lake Yamanaka (Fuji Five Lakes, Japan). This study presents a ... [more ▼]

High-resolution seismic profiles, combined with the integration of published drilling data, provide a detailed paleoenvironmental history of Lake Yamanaka (Fuji Five Lakes, Japan). This study presents a detailed analysis of the different depositional stages of the area currently occupied by Lake Yamanaka (floodplain wetland, river and lake). From ca. 5500 cal yr BP to ca. 5050 cal yr BP, the Yamanaka basin was occupied by floodplain wetlands. During that period, the landscape was very stable and erosion on northeastern flank of Mt. Fuji was relatively limited. From ca. 5050 cal yr BP to ca. 3050 cal yr BP, the water level increased and the floodplain wetlands became a lake. From ca. 3050 cal yr BP to ca. 2050 cal yr BP, the water level progressively decreased, leading to a reduction in lake extent. During this lowering of the lake's water level, a 1 km2 mass-transport deposit modified the physiography of the lake floor. From ca. 2050 cal yr BP to ca. 1050 cal yr BP, the lake disappeared and a river flowing towards the northwest occupied the depression. Ponds occupied morphological lows formed by mass transport deposits. From ca. 1050 cal yr BP to the present day, the lake water level rose again, connecting the ponds with the main lake. Since then, the lake water level has continued to rise to the current level. Lake water level fluctuations are the results of several factors that could be interconnected: (i) changes in precipitation rates; (ii) margin destabilization (the Yamanaka mass-transport deposit), (iii) changes in river inlets and therefore variation in water supplies, (iv) volcanic eruptions (scoria fall-out and lava flows) and (v) changes in vegetation cover. This study highlights the importance of coupling sediment cores and high-resolution seismic reflection profiling to identify lateral variation and modification of sedimentary inputs through time. [less ▲]

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See detailÉvaluation du risque karstique de la région de BOUKADIR (Chlef-Algérie)
Moulana, Meriem Lina ULiege; Guendouz, Mostefa; Hubert, Aurelia ULiege

Poster (2018, September)

La commune de Boukadir, (ex Charon) dans la wilaya de Chlef au nord-ouest d’Algérie, n’a jamais été classée parmi les régions karstiques d'Algérie malgré la grande doline d’effondrement en juin 1988 de ... [more ▼]

La commune de Boukadir, (ex Charon) dans la wilaya de Chlef au nord-ouest d’Algérie, n’a jamais été classée parmi les régions karstiques d'Algérie malgré la grande doline d’effondrement en juin 1988 de 60m de diamètre et 35m de profondeur sur la route nationale. Boukadir se trouve au piémont nord de la montagne de l’Ouarsenis, sur la bordure sud de la plaine de 20 km de large du bas Chelif traversée par Oued Chlef. Le piémont septentrional de la chaîne de Ouarsenis est composé de calcaire à Lithothamniée subhorizontal d’âge miocène supérieur (messinien). Au niveau de la plaine et de l'effondrement, les roches carbonatées sont recouvertes de sédiments plio-quaternaires, là où les infrastructures (RN4, autoroute Est-Ouest d’Algérie A1) et villages (Boukadir, 41 655 habitants) sont situés. Afin d'évaluer le risque karstique, nous combinons différentes approches... [less ▲]

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See detailPaleoearthquakes recorded in the Fuji Five Lakes during the last ca. 6000 years (Fuji Five Lakes, Japan
Lamair, Laura ULiege; Hubert, Aurelia ULiege; Yamamoto, Shinya et al

Conference (2018, May)

In Japan, one pioneering lacustrine paleoseismological study was conducted in Lake Biwa in the 1990s. However, despite the high seismicity of Japan, the field of lacustrine paleoseismology did not expand ... [more ▼]

In Japan, one pioneering lacustrine paleoseismological study was conducted in Lake Biwa in the 1990s. However, despite the high seismicity of Japan, the field of lacustrine paleoseismology did not expand. Paleoseismological studies were more focused on inland trenches and coastal records. The paleoseismological data obtained by that way covers the last ~6000 years but contains hiatuses. Using lacustrine sediment allows us to span the same time period and to have a continuous record. Here, we present the second lacustrine paleoseismological study conducted in Japan. The Fuji Five Lakes are situated close to the triple junction, where the North American Plate, the Eurasian plate and the Philippine Sea Plate meet. Therefore, the region can be impacted by megathrust earthquakes generated along the Nankai-Suruga and the Sagami subduction zones. In addition, intraplate earthquake may affect the Fuji Five Lakes region. In the framework of the QuakeRecNankai project, we investigated two of the Fuji Five Lakes, Lake Motosu and Lake Sai. Here, we present the paleoseismological record of Lake Motosu and Lake Sai over the last 6000 and 2000 years, respectively. The turbidites were identified based on geophysical (magnetic susceptibility, grainsize) and geochemical properties (XRD, XRF) as well as SEM analysis. The turbidites were dated by 210Pb/137Cs, 14C dating and correlated with historical earthquakes. For prehistorical earthquakes (i.e., before the 6th century), they were correlated with geological evidences recorded along the Eastern Honshu coastline (i.e., tsunami deposits, coastal uplift, emerged ridge beaches). Over the last 6000 years, seismo-turbidites occurred with a mean recurrence time of 184±8 years. The near absence of large mass-transport deposits in the last 6000 years suggest that earthquake shaking mostly induced the remobilization of thin veneers of sediments in Lake Motosu. In Lake Sai, the earthquake fingerprint differs from Lake Motosu. Over the last 1200 years, past earthquake shaking induced turbidites, delta collapse and liquefaction (sediment volcanoes). [less ▲]

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