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  • 1
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    Development and Emplacement of Ana Slide, Eivissa Channel, Western Mediterranean Sea (2022)
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    Publication Date: 2023-11-17
    Description: Submarine landslides can destroy seafloor infrastructures and generate devastating tsunamis. In spite of decades of research into the functioning of submarine landslides there are still numerous open questions, in particular how different phases of sliding influence each other. Here, we re‐analyze Ana Slide—a relatively small (〈1 km3) landslide offshore the Balearic Islands, which is unique in the published literature because it is completely imaged by high‐resolution 3D reflection seismic data. Ana Slide comprises three domains: (a) a source area that is almost completely evacuated with evidence of headscarp retrogression, (b) an adjacent downslope translational domain representing a by‐pass zone for the material that was mobilized in the source area, and (c) the deposit formed by the mobilized material, which accumulated downslope in a sink area and deformed slope sediment. Isochron maps show deep chaotic seismic units underneath the thickest deposits. We infer that the rapid deposition of the landslide material deformed the underlying sediments. A thin stratified sediment unit between three lobes suggests that Ana Slide evolved in two failure stages separated by several tens of thousands of years. This illustrates the problem of over‐estimating the volume of mobilized material and under‐estimating the complexity even of relatively simple slope failures without high‐quality 3D reflection seismic data.
    Description: Plain Language Summary: We investigate a submarine landslide in the Balearic Islands off Spain. The aim is to find out how such landslides work. This study is special because it can draw on a unique data set: the complete imaging of this landslide with high quality reflection seismic data. We find that previous studies have over‐estimated the volume of the mobilized material because deformed sediments below the landslide were also counted, and that the slide actually consisted of two individual slope failures that occurred at the same place but in distinct episodes separated by some tends of thousands of years. Together these results show that there is a large risk of overestimating landslide‐related tsunami hazards when this kind of reflection seismic data is not available.
    Description: Key Points: Ana Slide is completely covered by 3D reflection seismic data and its kinematic development is addressed. Large parts of the volume previously interpreted as landslide material was deformed in‐situ. Ana Slide developed during two separate phases that involved likely significantly smaller volumes of material than previously proposed.
    Description: Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659
    Description: GRC Geociències Marines
    Description: https://doi.pangaea.de/10.1594/PANGAEA.943506
    Description: https://doi.pangaea.de/10.1594/PANGAEA.943523
    Keywords: ddc:622.1592 ; submarine landslide ; kinematic analysis ; substrate deformation processes ; Mediterranean Sea ; emplacement mechanism
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Unknown
    Decline in Slope Stability as a Consequence of Gassy Soil in Submarine Slopes on the Balearic Promontory (2022)
    ASME
    Details
    Publication Date: 2022-11-22
    Description: Submarine landslides can entail a substantial hazard for offshore infrastructure as they are capable of triggering tsunamis and may develop into highly mobile turbidity currents capable of breaking seabed cables. Despite considerable research activity, the trigger mechanisms for such landslide events cannot be clearly defined. Recently, marine gas occurrence has been investigated as a possible trigger mechanism. The behaviour of a fine-grained gassy soil is influenced by a variety of micromechanical processes; amongst destructuring due to fracture formation or gas bubble expansion, and bubble flooding with subsequent cavity collapse. Capturing and modeling these processes in order to assess the destructive potential of enclosed gas bubbles in submarine slopes is to date a considerable scientific challenge. With the help of a large number of Finite Element Limit Analyses (FELA), which are based on laboratory tests on a gravity core from the western Mediterranean Sea, submarine slope stability in the respective region was evaluated. Based on these analyses, gassy soil can be defined as a preconditioning factor but not as a capable trigger mechanism for submarine landsliding.
    Type: Book chapter , NonPeerReviewed , info:eu-repo/semantics/bookPart
    Format: text
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    PAPER (OCEANREP)
  • 3
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    Unknown
    Characterisation of Submarine Landslides on the Eastern Slopes of the Eivissa Channel, Western Mediterranean Sea (2023)
    Details
    Publication Date: 2024-04-16
    Description: Submarine landslides pose a risk to offshore infrastructure and can generate devastating tsunamis. There exist a range of hypotheses about pre-conditioning factors and trigger mechanisms, yet the understanding of landslide development and emplacement processes has been limited to a few case studies. On the one hand, this is partly because the study of sub-seafloor structures is limited to sediment echosounder profiles and 2D and rarely 3D reflection seismic data. However, because these data are expensive to acquire, data coverage is sparse and often of low resolution. On the other hand, historical records of landslide- generated tsunamis are rare, and can often not be differentiated from tsunamis generated exclusively by earthquakes. In addition, the study of active slope failures is mainly based on the 2D and 3D reflection seismic analysis of their remnants – the mass transport deposits (MTDs) – meaning that slope failure development and emplacement processes can only be interpreted from these remains. Interpretation of reflection seismic data is a highly ambiguous task and depends on the data which includes resolution and penetration depth and the experience of the interpreter. Monitoring of active failure processes has only been successful to a limited extent, for instance by measurements of landslide velocities deduced from telecommunication cable breaks. Because of the large size of submarine landslides, it is becoming more and more evident that they can deform seafloor sediments to significant depth. Furthermore, stations and platforms installed directly on the seafloor can be damaged or buried by landslide material or even be incorporated into the slope failure.
    Type: Thesis , NonPeerReviewed
    Format: text
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    PAPER (OCEANREP)
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