The ASTARTE Paleotsunami and Mass Transport Deposits data bases – web-based references for tsunami and submarine landslide research around Europe

EU project ASTARTE aims at developing a higher level of tsunami hazard assessment in the North East Atlantic, Mediterranean and Connected seas (NEAM) region by a combination of field work, experimental work, numerical modeling and technical development. The project is a cooperative work of 26 institutes from 16 countries and links together the description of past tsunamigenic events, the identification and characterization of tsunami sources, the calculation of the impact of such events, and the development of adequate resilience and risks mitigation strategies (www.astarte.eu). Within ASTARTE two web-based data bases on Paleotsunami and Mass Transport Deposits in the NEAM areas were created with the purpose to be the future information repositories for tsunami research in Europe.The aim is to integrate every existing official scientific reports and peer reviewed papers on these topics and update on new entries every 6-12 months, hosting information and detailed data, that are crucial e.g for tsunami modeling. A relational database managed by ArcGIS for Desktop 10.x software has been implemented. One of the final goals of the project is the public sharing of the archived datasets through a web-based map service that will allow visualizing, querying, analyzing, and interpreting all datasets. The interactive map service will be hosted by ArcGIS Online and will deploy the cloud capabilities of the portal. Any interested users will be able to access the online GIS resources through any Internet browser or specific apps that run on desktop machines, smartphones, or tablets and will be able to use the analytical tools, key tasks, and workflows of the service.We will present the data bases structure and topics as well as their ArcGIS Online version. The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under grant agreement n 603839 (Project ASTARTE - Assessment, Strategy and Risk Reduction for Tsunamis in Europe).PublishedWien, Austria5T. Modelli di pericolosità sismica e da maremot

Speciale: Il terremoto ligure del 23 Febbraio del 1887

L'educazione e la formazione sono due ingredienti che consentono ai cittadini di apprendere le informazioni scientifiche altrimenti confinate nei laboratori in particolare nel campo del rischio ambientale. E in questa ottica che è nato il programma O3E (acronimo in francese di Osservazione dell'Ambiente a scopo Educativo per le Scuole). II programma O3E fa seguito a un periodo di sperimentazione di 10 anni (1997-2007) in cui sono nati diversi progetti nazionali (Sismos a l'Ecole, EDURISK, climAtscope). L'obiettivo generale del programma O3E è mettere in rete istituti scolastici nelle regioni delle Alpi latine equipaggiate con sensori di parametri ambientali di tipo educativo. I dati sul movimento del suolo (sismometri), sulle temperature e la pluviometria (stazioni meteo), sulle risorse idriche (idrogeologia) registrati negli istituti scolastici sono raccolti su server dedicati poi messi a disposizione attraverso Internet alla comunità educativa. La rete O3E così strutturata, diventa il punto di partenza per varie attività di insegnamento delle geoscienze e di educazione al rischio naturale e si propone di: - promuovere le scienze sperimentali e le nuove tecnologie - mettere in rete gli attori dell'educazione e della formazione - sviluppare il senso di autonomia e la responsabilità dei giovani - rafforzare e sviluppare i legami con i partner regionali nel campo educativo e universitario - favorire una presa di coscienza razionale dei problemi legati alla prevenzione dei rischi naturali e del patrimonio geologico, ciò che può fare la differenza durante un evento in termini di sicurezza. Tenendo conto degli orientamenti del programma, che dà un grande spazio alle tecnologie di comunicazione, della sua dimensione educativa (sensibilizzazione ai rischi ambientali), del suo contenuto scientifico (geoscienze), e della sua importanza su scala regionale e persino internazionale (messa in rete di istituti scolastici), vengono avviate iniziative da parte degli istituti scolastici in stretta collaborazione con il mondo dell'Università e della Ricerca. E' il caso del presente opuscolo che tratta il caso di un terremoto emblematico per le regioni interessate da O3E: il terremoto di Imperia - Mentone del 23 febbraio 1887. I dati raccolti qui (archivi, sismogrammi, ultimi studi oceanografici. .. ) consentiranno agli studenti e ai loro insegnanti di affrontare un caso di studio.CG06, Region PACA, DIREN PACA, Sciences a l'Ecole; ALCOTRAPublished5.9. Formazione e informazioneope

Earthquakes, The hows and whys. Focus on The February 23, 1887 Ligurian earthquake

Education and training are two ingredients that allow citizens to learn scientific information otherwise confined within laboratories, in particular in the field of environmental risk. It is in this perspective that the O3E (French acronym for European Observatory for Education and Environment) project was born. The O3E project is the follow up of a 10 year long testing phase (1997-2007) during which several national projects ("Sismos a I'Ecole", "EDURISK" and "climAtscope") were born. The overall objective of the O3E program is to network educational institutions, which are equipped with educational instruments and sensors to measure environmental parameters, across regions of the Latin Alps. Data on ground motion (seismometers), temperatures and rainfall (weather stations), on water resources (hydrogeology) recorded in schools are collected on dedicated servers, which are then made available to the educational community through the Internet. The so-structured O3E network becomes the starting point for many geosciences teaching and educational activities to natural hazards in order to: - promote experimental sciences and new technologies - network the actors involved in education and training - develope the sense of autonomy and responsibility in young people - strenghten and develope relations with regional partners in the field of education and academia - foster rational awareness of the problems related to the geological heritage and to the prevention of natural hazards, that is what can make the difference, in terms of safety, when an event occurs. Taking into account the guidelines of the program (which gives a large space to communication technologies), its educational dimension (awareness of environmental risks), its scientific content (geosciences), and its importance on a regional and even international scale (networking of schools), initiatives are started up by schools in close cooperation with the university and research community. As it is the case of this pamphlet dealing with an earthquake, which is emblematic for the regions involved in the O3E project: the Imperia -Menton earthquake occurred on February 23,1887. The data collected here (archives, seismograms, recent oceanographic studies ... ) will enable students and their teachers to deal with a case study.CG 06, Région PACA, DIREN PACA, Sciences à l'Ecole; Alcotra, EUPublished5.9. Formazione e informazioneope

The last glacial maximum Balearic Abyssal Plain megabed revisited

Megabeds are thick sedimentary layers extending over thousands square kilometres in deep sea basins and are thought to result from large slope failures triggered by major external events. Such deposits have been found in at least three areas of the Mediterranean Sea. Although their discovery dates back to the early 1980s, many questions remain, concerning their initiation, source area, extent, and the nature of their emplacement. One of the largest previously documented megabeds was emplaced during the Last Glacial Maximum across the Balearic Abyssal Plain with a thickness of 8-10 m in water depths of up to 2800 m. New 3.5 kHz sub-bottom profiles and sediment cores provide greater constraint on the lateral variability of the megabed and allow to map it beyond previous estimates, with a revised areal extent up to 90,000-100,000 km2. Megabed terminations show gradual pinch-out to the West and an abrupt eastward termination against the Sardinia steep margin. The megabed presents both in seismic profiles and in sediment cores a tripartite subdivision likely corresponding to changes in flow regimes across the basin with a central area of sandy facies and erosional base oriented NNE-SSW allowing renewed discussions about sources and trigger of the megabed

Morpho-Structural Setting of the Ligurian Sea: The Role of Structural Heritage and Neotectonic Inversion

The review of recent bathymetric and geophysical data collected in the framework of several research and cartographic projects have allowed a detailed reconstruction of the morpho-structural setting and the (neo)tectonic evolution for both the Alpine and Apennine margins of the Ligurian Sea (Italy). The widespread occurrence of erosional processes and sediment mass movements along the steep continental slope and within the system of submarine canyons reflect the close correlation between the active tectonics and the recent morpho-dynamic evolution of the Ligurian Margin. This relation is better constrained in the western sector (Alpine) of the Ligurian Sea, where the recent uplift of the continental margin is associated to a well-developed system of inherited structures reactivated under a compressive/transpressive regime and widespread seismicity. In the eastern sector, where the seismicity is lower or absent, the mass movements are limited to few areas (e.g., the Portofino slope) coinciding with seismic clusters. Additionally, this sector is characterized by moderate and episodic fault reactivations under a compressive regime. The evidence of compressive deformation along the inherited fault systems has been revealed in some areas of the Ligurian Sea where the post-drifting extensional tectonics is interrupted by episodic tectonic inversion (at least) during the Middle–Upper Miocene and the Plio–Pleistocene until present

THE MEDITERRANEAN SEA: A NATURAL LABORATORY TO STUDY GAS HYDRATE DYNAMICS?

International audienceGas hydrates have been proven by coring at one site in the (eastern) Mediterranean Sea, but their wider extent remains uncertain. Here we present results from investigations of the potential Mediterranean gas hydrate system, suggesting that clathrates occur more widely and have been strongly impacted by glacial-interglacial climate forcing. Modeling of the methane hydrate stability zone (MHSZ) shows it to be present in most of the Mediterranean Sea, albeit in deep waters (>1000 m) due to warm bottom waters (12.5-14°C) and in greater thicknesses (200-500 m) in the geothermally cooler eastern basin. Comparison of the MHSZ with known or possible zones of gas flux to seabed suggests prospective areas for hydrate occurrence, mainly in the eastern basin. One is the Nile fan, where evidence of the first BSR in the Mediterranean Sea (presented sseparately, Praeg et al. this volume) confirms the potential for additional hydrate discoveries. During glacial stages, gas hydrate stability in the Mediterranean increased due to bottom waters up to 4°C cooler; even allowing for sea levels 125 m lower, the modeled glacial-stage MHSZ was up to 25% thicker and 300 m shallower on basin margins. Glacial-to-interglacial transitions thus corresponded to a marked reduction in hydrate stability, with downslope migration of the upper limit of the MHSZ across depths of c. 700-1000 m. A compilation of submarine landslides in the Mediterranean Sea indicates a peak in the age of slide deposits during the last deglaciation and includes abundant headwalls in mid-to upper slope depths (<1200 m), including on the Nile fan. Together these results suggest that the Mediterranean Sea, in particular its gas-rich eastern basin, offers natural laboratory conditions to test the hypothetical linkages between climate-driven changes in gas hydrate stability and slope instabilities over glacial-interglacial timescales

Erosional and Depositional Features of Glacial Meltwater Discharges on the Eastern Canadian Continental Margin

Large-scale glacial meltwater discharges have long been recognized as important sedimentological agents on the eastern Canadian continental margin. Previous studies in Eastern Valley of Laurentian Fan and Orphan Basin have elucidated aspects of processes and timing of glacial discharges, principally from seismic-reflection profiles and deep-water sidescan sonar. New multibeam bathymetry and piston cores show evidence of important meltwater processes seaward of all transverse troughs on the continental shelf, from Hudson Strait to the Scotian margin. Meltwater cuts broad flat-floored valleys and sculpts residual buttes, depositing thick-bedded gravel and sand turbidites, and builds submarine fans. Based on morphology, a wide range of scales of meltwater discharge may take place. Meltwater is intimately linked with supply of fluid glacial diamict (till) that on gentler slopes (\u3c 2.5°) creates glacigenic debris flows but on steeper slopes breaks up, entrains water, and transforms to create erosive turbidity currents. Three end-member processes are recognized on submarine fans seaward of transverse troughs that were occupied by ice streams: glacigenic debris flows, turbidity-current deposition of channel–levee complexes, and blocky mass-transport deposits resulting from debris avalanches. The relative importance of meltwater appears greater at lower than at higher latitudes, whereas the formation of glacigenic debris flows is dependent on gradient. Pleistocene processes have resulted in slopes that are graded, implying that most sand deposition was on the continental rise

Contourite identification along Italian margins: The case of the Portofino drift (Ligurian Sea)

A brief review of the published evidence of current deposits around Italy is the occasion to test the robustness of matching bottom current velocity models and seafloor morphologies to identify contourite drifts not yet documented. We present the result of the regional hydrodynamic model MARS3D in the Northern Tyrrhenian and Ligurian Sea with horizontal resolution of 1.2 km and 60 levels with focus on bottom current: data are integrated over summer and winter 2013 as representative of low and high intensity current conditions. The Eastern Ligurian margin is impacted by the Levantine Intermediate Water (LIW) with modeled mean velocity of bottom current up to 20 cm s−1 in winter 2013 and calculated bottom shear stress exceeding 0.2 N m−2 in water depth of 400–800 m. By crossing this information with seafloor morphology and geometry of seismic reflections, we identify a sediment drift formerly overlooked at ca 1000 m water depth. The Portofino separated mounded drift has a maximum thickness of at least 150 m and occurs in an area of mean current velocity minimum. Independent evidence to support the interpretation include bottom current modelling, seafloor morphology, seismic reflection geometry and sediment core facies. The adjacent areas impacted by stronger bottom currents present features likely resulted from bottom current erosion such as a marine terrace and elongated pockmarks. Compared to former interpretation of seafloor morphology in the study area, our results have an impact on the assessment of marine geohazards: submarine landslides offshore Portofino are small in size and coexist with sediment erosion and preferential accumulation features (sediment drifts) originated by current-dominated sedimentary processes. Furthermore, our results propel a more general discussion about contourite identification in the Italian seas and possible implications

Positive-relief carbonate pavements on the central Nile deep-sea fan : gas hydrate blisters or carbonate-filled pockmarks?

International audienceThe Nile deep-sea fan is rich in fluid vents, including a Central Province of acoustically reflective patches that correspond at seafloor to fractured carbonate pavements hosting chemosynthetic ecosystems. The backscatter patches (BPs) have been referred to as pockmarks, but several studies have noted positive relief. We examine the BPs by integrating older multibeam datasets (50-100 m DTMs) with sonar imagery of higher resolution acquired in 2010 (APINIL campaign) using a hull-mounted multibeam (30 kHz, 10-25 m DTMs) and a deep-towed sidescan (180 kHz, 1.5 m pixels. We recognise at least 450 BPs in water depths of 1550-2700 m, sub-circular to elongate and 70-600 m wide, almost all of positive relief up to 7 m. The BPs vary in backscatter intensity on both 30 kHz and 180 kHz imagery, and differ in character between them. We attribute this to varying sediment penetration by the two systems, which respectively integrate impedance contrasts to depths of 3 m and 0.1 m. At local deposition rates, this corresponds to timescales of 5-100 ka. In the absence of erosion, backscatter variations and fractures observed on 180 kHz imagery suggest shifting patterns of carbonate growth and breakage over the last 5 ka. Four water column gas flares observed in 2010 in high backscatter areas suggest on-going carbonate cementation. Previous studies of the area indicate downward growth of carbonate pavements, at rates much less than those of burial, and it has been proposed that self-sealing drives the outward growth of broad pavements. However, such a process does not generate stress fields and should result in buried lenses of zero relief. We propose that the elevated and fractured seafloor carbonates we observed as BPs record interactions with underlying gas hydrates. One possibility is that BPs are ‘hydrate blisters’, comprising thin carbonates above growing gas hydrate lenses; however, the lack of deflated features (hydrate pockmarks) is puzzling. Another possibility is that fracturing in response to hydrate formation and dissolution allows fluid migration through recurrently buried pavements, resulting in the upward growth of mixed carbonate-sediment mounds that overfill hydrate pockmarks. We intend to test these hypotheses during the SEAGAL campaign of the RV Pourquoi pas?, scheduled for September 2020. This work has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 656821

Strong Site Effect Revealed by a New Broadband Seismometer on the Continental Shelf Offshore Nice Airport (Southeastern France)

A broadband seismological station (PRIMA) installed offshore Nice airport (southeastern France) reveals a strong amplification effect of seismic waves. PRIMA station was in operation for 2 years (9/2016 to 10/2018) on the outer shelf at a water depth of 18 m. Situated at the mouth of the Var River, this zone is unstable and prone to landslides. A catastrophic landslide and tsunami already occurred in 1979, causing 10 casualties. Given the level of seismicity of the area, it is important to infer the impact of an earthquake on this zone. We analyze the recordings of earthquakes and seismic noise at the PRIMA station by comparing them to nearby inland stations. We find that the seismic waves are strongly amplified at PRIMA at some specific frequencies (with an amplification factor greater than 10 at 0.9 Hz). Using geological and geophysical data, we show that the main amplification frequency peak (at 0.9 Hz) is due to the velocity contrast between the Pliocene sedimentary layer and fine-grained sediments dated from the Holocene, at about 100 m depth. This velocity contrast is also present along the Var valley, but the level of amplification detected on PRIMA station is larger. Using numerical simulations of seismic waves in a 2D model that accounts for the pinch-out geometry related to the termination of the Holocene sedimentary layer, we can partially explain this amplification. This offshore site effect could have a crucial impact on the triggering of a submarine landslide by an earthquake in this region. More generally, this effect should be taken into account for the modeling of landslides and induced tsunamis triggered by seismic waves