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  • 1
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    Development and Emplacement of Ana Slide, Eivissa Channel, Western Mediterranean Sea (2022)
    Details
    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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    Evolutionary development and volume balance calculations of the Ana Slide in the Eivissa Channel, Western Mediterranean (2021)
    In:  [Poster] In: 81. Jahrestagung der Deutschen Geophysikalischen Gesellschaft (DGG), 01.03.-05.03.2021, Kiel (online) .
    Details
    Publication Date: 2021-07-13
    Description: Submarine landslides are widespread phenomena on continental slopes and act as prime sediment transport processes between shallow and deep marine regions. In addition, they pose significant risk to coastal communities worldwide. Within this study, we focus on the Ana Slide, a relatively small landslide with areal extent of 4.7 km2located at water depth between 635 –905 m on the eastern slopes of the Eivissa Channel, western Mediterranean. Predominant sediment types are high-water content, carbonate-dominated hemipelagic deposits susceptible to high pore pressures and liquefaction. Available data include very-high resolution bathymetric and a 3D seismic dataset completely covering the landslide.The Ana Slide is characterised by three landslide domains: the 1) evacuational or headwall domain, 2) translational domain, and 3) accumulational or toe domain. While the headwall domain demonstrates classic features of material evacuation and poses as the exclusive source of material within the landslide process, the translational domain documents extensive in-situ remnant blocks which were unaffected during failure. Instead, landslide material from the evacuational domain moved up and over the translational domain. The toe domain exhibits extensive chaotic seismicfacies with compressional ridges throughout the deposit and imprinted onto the seafloor. Even though extensive chaotic seismic facies characterise the toe domain, its volume differs significantly from the volume of the evacuated material from the headwall domain. Thus, we conclude that the chaotic seismic facies does not represent landslide material. Instead, the in-situ sediment underwent a range of soft-sediment deformation processes. We propose two mechanisms responsible for this deformation: loading-and shearing-induced soft-sediment deformation resulting from rapid deposition of overburden material. Under consideration of the likely elevated pore pressure and liquefaction potential of deposits, these mechanisms lead to the destruction and disturbanceof internal reflections.Our analysis demonstrates the difficulties in distinguishing between actually failed landslide material and deformed but not translated sediment, which may well lead to erroneous landslide volume estimations. Our new model of the evolutionary development of the Ana Slide may well hold for many other submarine landslides globally, the volumes of which could be significantly overestimated.
    Type: Conference or Workshop Item , NonPeerReviewed
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  • 3
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    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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  • 4
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    A new methodology to assess the potential of conjectural trigger mechanisms of submarine landslides exemplified by marine gas occurrence on the Balearic Promontory (2021)
    Elsevier
    Details
    Publication Date: 2024-02-07
    Description: Highlights • full constitutive model parameter set of marine soil for MCC. • workflow for studies of potential trigger mechanisms exemplified by marine gas occurrence. • quantitative estimation of slope stability (by FOS) on the Balearic Promontory. • Gassy soil can be considered a preconditioning factor, not a trigger mechanism. Abstract The destructive potential of submarine landslides for populated coastal areas and maritime infrastructure has been described many times. However, the geological processes that can trigger such landslide events have not yet been fully established. In order to be able to conclusively assess the trigger potential of these processes, a quantification of the slope stability is indispensable. This requires a precise knowledge of the geotechnical and geological boundary conditions before and after the investigated landslide event, as well as the change in these boundary conditions caused by the alleged trigger mechanism. In order to make these described preconditions and the work process generally applicable, a universally adaptable methodology for the identification of trigger mechanisms was developed. Here it is successfully applied to marine gas occurrence, which has recently been considered as a trigger mechanism due to the negative influence of enclosed gas bubbles on the shear strength of fine-grained soils. The constitutive model by Sultan and Garziglia (2014) is applied to simulate the gas-influenced undrained shear strength of a marine soil from a sediment starved margin on the Balearic Promontory and a range of Finite Element Limit Analyses (FELA) are conducted to determine the resulting loss of stability of different slope geometries. Within the scope of these calculations, the first set of Modified Cam Clay model parameters for a soil from the western Mediterranean is introduced. Based on the simulations, it can be concluded that marine gas occurrence decreases the overall stability of a slope compared to the saturated state. However, it also becomes obvious that the prevailing slope geometries with low inclinations are stable with a substantial capacity reserve for all simulated scenarios. Conclusively, gassy soil can be designated as a preconditioning factor decreasing the slope stability, as the state of failure can only be reached if the slope was in a precarious state before, or in combination with other impacts.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
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  • 5
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    Development and Emplacement of the Ana Slide, Eivissa Channel, Western Mediterranean Sea (2022)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Submarine landslides can destroy seafloor infrastructure and generate devastating tsunamis, but 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-analyse the Ana Slide - a relatively small (〈1 km3) landslide in the Balearic Islands, which is unique because it is completely imaged by high-resolution 3D seismic data. The Ana Slide comprises three domains: (i) a source area that is almost completely evacuated with evidence of headscarp retrogression; (ii) an adjacent downslope translational domain representing a bypass zone for the material that was mobilized in the source area, and (iii) the deposit formed by the mobilized material, which accumulated downslope in a sink area. Isochron maps show deep chaotic seismic units underneath the thickest deposits. We infer that rapid deposition of the landslide material deformed the underlying sediments. A thin stratified sedimentary unit between three lobes shows that the Ana Slide evolved in two failure stages separated by several tens of thousands of years. This illustrates the danger of over-estimating the volume of mobilized material and under-estimating the complexity even of relatively simple slope failures without high-quality seismic data.
    Type: Article , PeerReviewed
    Format: text
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