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  • 1
    Publication Date: 2020-02-06
    Description: The 1908 Messina tsunami was the most catastrophic tsunami hitting the coastline of Southern Italy in the younger past. The source of this tsunami, however, is still heavily debated, and both rupture along a fault and a slope failure have been postulated as potential origin of the tsunami. Here we report a newly discovered active Fiumefreddo-Melito di Porto Salvo Fault Zone (F-MPS_FZ), which is located in the outer Messina Strait in a proposed landslide source area of the 1908 Messina tsunami. Tsunami modeling showed that this fault zone would produce devastating tsunamis by assuming slip amounts of ≥5 m. An assumed slip of up to 17 m could even generate a tsunami comparable to the 1908 Messina tsunami, but we do not consider the F-MPS_FZ as a source for the 1908 Messina tsunami because its E-W strike contradicts seismological observations of the 1908 Messina earthquake. Future researches on the F-MPS_FZ, however, may contribute to the tsunami risk assessment in the Messina Strait.
    Type: Article , PeerReviewed
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  • 2
    Publication Date: 2019-09-23
    Description: Determining factors that limit coseismic rupture is important to evaluate the hazard of powerful subduction zone earthquakes such as the 2011 Tohoku-Oki event (Mw = 9.0). In 1960 (Mw = 9.5) and 2010 (Mw = 8.8), Chile was hit by such powerful earthquakes, the boundary of which was the site of a giant submarine slope failure with chaotic debris subducted to seismogenic zone depth. Here, a continuous décollement is absent, whereas away from the slope failure, a continuous décollement is seismically imaged. We infer that underthrusting of inhomogeneous slide deposits prevents the development of a décollement, and thus the formation of a thin continuous slip zone necessary for earthquake rupture propagation. Thus, coseismic rupture during the 1960 and 2010 earthquakes seems to be limited by underthrusted upper plate mass-wasting deposits. More generally, our results suggest that upper plate dynamics and resulting surface processes can play a key role for determining rupture size of subduction zone earthquakes
    Type: Article , PeerReviewed
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  • 3
    Publication Date: 2019-09-23
    Description: Lake Ohrid, located on the Balkan Peninsula within the Dinaride–Albanide–Hellenide mountain belt, is a tectonically active graben within the South Balkan Extensional Regime (SBER). Interpretation of multichannel seismic cross sections and bathymetric data reveals that Lake Ohrid formed during two main phases of deformation: (1) a transtensional phase which opened a pull-apart basin, and (2) an extensional phase which led to the present geometry of Lake Ohrid. After the initial opening, a symmetrical graben formed during the Late Miocene, bounded by major normal faults on each side in a pull-apart type basin. The early-stage geometry of the basin has a typical rhomboidal shape restricted by two sets of major normal faults. Thick undisturbed sediments are present today at the site where the acoustic basement is deepest, illustrating that Lake Ohrid is a potential target for drilling a long and continuous sediment core for studying environmental changes within the Mediterranean region. Neotectonic activity since the Pliocene takes place along the roughly N–S-striking Eastern and Western Major Boundary Normal Faults that are partly exposed at the present lake floor. The tectono-sedimentary structure of the basin is divided into three main seismic units overlying the acoustic basement associated with fluvial deposits and lacustrine sediments. A seismic facies analysis reveals a prominent cyclic pattern of high- and low-amplitude reflectors. We correlate this facies cyclicity with vegetation changes within the surrounding area that are associated with glacial/interglacial cycles. A clear correlation is possible back to ca. 450 kyrs. Extrapolation of average sedimentation rates for the above mentioned period results in age estimate of ca. 2 Myrs for the oldest sediments in Lake Ohrid.
    Type: Article , PeerReviewed
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  • 4
    Publication Date: 2017-11-07
    Description: High-resolution reflection seismic data obtained around Gran Canaria allow a detailed and consistent correlation of seismic reflectors of the northern and southern Canary Basins with the lithology drilled by DSDP Leg 47A SSE of Gran Canaria, as well as with major phases of volcanic activity on Gran Canaria as mapped onshore. Two prominent reflectors were chosen as marker horizons and correlated with the drilled lithology. the results indicate that reflector R7 above the Miocene volcaniclastic debris flows V1-V3 reflects the shield-building phase of Gran Canaria. Reflector R3 is interpreted as corresponding with the Pliocene Roque Nublo formation. The top of the massive island flank of Gran Canaria, defined by seismically chaotic facies, extends 44 to 72 km off the coast of Gran Canaria. West of Gran Canaria the flank of Tenerife onlaps the steeper and older flank of Gran Canaria, which, in turn, is onlapping the older flank of Fuerteventura to the east in a similar way. Erosional channels, which can also be traced up to 50 km from the area between Gran Canaria and Fuerteventura into the deeper northern basin, have been identified in the bathymetry. The data presented provide new detailed information for modelling the submarine and subaerial evolution of the central Canary Islands of Gran Canaria and Tenerife, i.e. the timing of their shield-building phases and later stages of major volcanic activity, as reflected by the position of prominent seismic reflectors in the seismic stratigraphy.
    Type: Article , PeerReviewed
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  • 5
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    Springer International Publishing
    In:  In: Submarine Mass Movements and their Consequences. Advances in Natural and Technological Hazards Research, 41 . Springer International Publishing, pp. 291-300. ISBN 978-3-319-20978-4
    Publication Date: 2019-09-23
    Description: Lake Ohrid (LO), a transboundary lake shared by Macedonia and Albania on the Balkan Peninsula, is not only considered to be the oldest lake in Europe (~2 Ma) but has a long and continuous sedimentary history. An advantage at LO is the availability of hydroacoustic data sets of good quality covering the entire lake basin. The tectonically formed basin is filled with thick undisturbed sediments. However, the overall internal structure of LO is characterized by numerous faults, clinoform structures, and several Mass Transport Deposits (MTDs). By using a seismic chronology model (SCM) correlating seismic reflector packages with Marine Isotope Stages (MIS) we estimate the occurrence of the deepest MTD detected in the southern basin at the transition of MIS9 to MIS8 (~300 ka) defining the onset of the sliding history in LO that is still ongoing today. In general, MTDs are widespread within the basin but they do cluster at active faults. Two large MTDs occurred in the early MIS7 (~230 ka, ~220 ka) and after a quiesence period of about ~70 ka two additional large MTDs have been detected in the late penultimate glacial period MIS6 (~150 ka, 130 ka). MIS5 seemed to be another quiet period with respect to mass wasting. In the younger sedimentary history mass movement is a common process with several large and mid-sized deposits mapped at all stratigraphic levels. The youngest slide deposits are estimated to occur within the last 2,000 years. The main outcome of this paper is a model for the spatial and temporal distribution of mass wasting for Lake Ohrid.
    Type: Book chapter , NonPeerReviewed
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  • 6
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    Springer International Publishing
    In:  In: Submarine Mass Movements and their Consequences : 7th International Symposium. , ed. by Lamarche, G. Springer International Publishing, Cham, pp. 145-154.
    Publication Date: 2017-11-22
    Description: Agadir Canyon is one of the largest submarine canyons in the World, supplying giant submarine sediment gravity flows to the Agadir Basin and the wider Moroccan Turbidite System. While the Moroccan Turbidite System is extremely well investigated, almost no data from the source region, i.e. the Agadir Canyon, are available. New acoustic and sedimentological data of the Agadir Canyon area were collected during RV Maria S. Merian Cruise 32 in autumn 2013. The data show a prominent headwall area around 200 km south of the head of Agadir Canyon. The failure occurred along a pronounced weak layer in a sediment wave field. The slab-type failure rapidly disintegrated and transformed into a debris flow, which entered Agadir Canyon at 2500 m water depth. Interestingly, the debris flow did not disintegrate into a turbidity current when it entered the canyon despite a significant increase in slope angle. Instead, the material was transported as debrite for at least another 200 km down the canyon. It is unlikely that this giant debris flow significantly contributed to the deposits in the wider Moroccan Turbidite System.
    Type: Book chapter , NonPeerReviewed
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  • 7
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    Springer International Publishing
    In:  In: Submarine Mass Movements and Their Consequences : 7th International Symposium. , ed. by Lamarche, G., Mountjoy, J., Bull, S. and Hubble, T. Advances in Natural and Technological Hazards Research, 37 . Springer International Publishing, Cham, pp. 419-426. ISBN 9783319209784
    Publication Date: 2021-05-11
    Description: Submarine spreading is a type of mass movement that involves the extension and fracturing of a thin surficial layer of sediment into coherent blocks and their finite displacement on a gently sloping slip surface. Its characteristic seafloor signature is a repetitive pattern of parallel ridges and troughs oriented perpendicular to the direction of mass movement. We map ~30 km2 of submarine spreads on the upper slope of the Hikurangi margin, east of Poverty Bay, North Island, New Zealand, using multibeam echosounder and 2D multichannel seismic data. These data show that spreading occurs in thin, gently-dipping, parallel-bedded clay, silt and sandy sedimentary units deposited as lowstand clinoforms. More importantly, high-amplitude and reverse polarity seismic reflectors, which we interpret as evidence of shallow gas accumulations, occur extensively in the fine sediments of the upper continental slope, but are either significantly weaker or entirely absent where the spreads are located. We use this evidence to propose that shallow gas, through the generation of pore pressure, has played a key role in establishing the failure surface above which submarine spreading occurred. Additional dynamic changes in pore pressure could have been triggered by a drop in sea level during the Last Glacial Maximum and seismic loading.
    Type: Book chapter , NonPeerReviewed
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  • 8
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    Geological Society London
    In:  In: Subaqueous Mass Movements and their Consequences: Advances in Process Understanding, Monitoring and Hazard. , ed. by Georgiopoulou, A. Special Publications Geological Society London, 500 . Geological Society London, London, pp. 13-26.
    Publication Date: 2020-08-03
    Description: Volcanic archipelagos are a source of numerous on- and offshore geohazards, including explosive eruptions and potentially tsunamigenic large-scale flank-collapses. Fogo Island in the southern Cape Verdes is one of the most active volcanoes in the world, making it both prone to collapse (as evidenced by the ca. 73 ka Monte Amarelo volcanic flank-collapse), and a source of widely-distributed tephra and volcanic material. The offshore distribution of the Monte Amarelo debris avalanche deposits and the surrounding volcaniclastic apron were previously mapped using only medium-resolution bathymetric data. Here, using recently acquired, higher resolution acoustic data, we revisit Fogo's flank-collapse, and find evidence suggesting that the deposition of hummocky volcanic debris originating from the failed eastern flank most likely triggered the contemporaneous, multi-phase failure of pre-existing seafloor sediments. Additionally, we identify, for the first time, multiple mass-transport deposits in the southern part of the volcaniclastic apron of Fogo and Santiago based on the presence of acoustically chaotic deposits in parametric echo sounder data and volcaniclastic turbiditic sands in recovered cores. These preliminary findings indicate a long and complex history of instability on the southern slopes of Fogo and suggest that Fogo may have experienced multiple flank collapses.
    Type: Book chapter , NonPeerReviewed
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  • 9
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    Geological Society London
    In:  In: Subaqueous Mass Movements and their Consequences: Advances in Process Understanding, Monitoring and Hazard Assessments. , ed. by Georgiopoulou, A. Special Publications Geological Society London, 500 . Geological Society London, London, pp. 551-566.
    Publication Date: 2020-08-03
    Description: The Tuaheni Landslide Complex (TLC) is characterised by areas of compression upslope and extension downslope. It has been thought to consist of a stack of two genetically linked landslide units identified on seismic data. We use 3D seismic reflection, bathymetry data, and IODP core U1517C (Expedition 372), to understand the internal structures, deformation mechanisms and depositional processes of the TLC deposits. Unit II and Unit III of U1517C correspond to the two chaotic units in 3D seismic data. In the core, Unit II shows deformation whereas Unit III appears more like an in situ sequence. Variance attribute analysis shows that Unit II is split in lobes around a coherent stratified central ridge and is bounded by scarps. By contrast, we find that Unit III is continuous beneath the central ridge and has an upslope geometry that we interpret as a channellevee system. Both units show evidence of lateral spreading due to the presence of the Tuaheni Canyon removing support from the toe. Our results suggest that Unit II and Unit III are not genetically linked, that they are separated substantially in time and they had different emplacement mechanisms, but fail under similar circumstances.
    Type: Book chapter , NonPeerReviewed
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  • 10
    Publication Date: 2023-02-08
    Description: A site at the gas hydrate stability limit was investigated offshore northwestern Svalbard to study methane transport in sediment. The site was characterized by chemosynthetic communities (sulfur bacteria mats, tubeworms) and gas venting. Sediments were sampled with in‐situ porewater collectors and by gravity coring followed by analyses of porewater constituents, sediment and carbonate geochemistry, and microbial activity, taxonomy, and lipid biomarkers. Sulfide and alkalinity concentrations showed concentration maxima in near‐surface sediments at the bacterial mat and deeper maxima at the gas vent site. Sediments at the periphery of the chemosynthetic field were characterized by two sulfate‐methane transition zones (SMTZ) at ~204 and 45 cm depth, where activity maxima of microbial anaerobic oxidation of methane (AOM) with sulfate were found. Amplicon sequencing and lipid biomarker indicate that AOM at the SMTZs was mediated by ANME‐1 archaea. A 1D numerical transport reaction model suggests that the deeper SMTZ‐1 formed on centennial scale by vertical advection of methane, while the shallower SMTZ‐2 could only be reproduced by non‐vertical methane injections starting on decadal scale. Model results were supported by age distribution of authigenic carbonates, showing youngest carbonates within SMTZ‐2. We propose that non‐vertical methane injection was induced by increasing blockage of vertical transport or formation of sediment fractures. Our study further suggests that the methanotrophic response to the non‐vertical methane injection was commensurate with new methane supply. This finding provides new information about for the response time and efficiency of the benthic methane filter in environments with fluctuating methane transport.
    Type: Article , PeerReviewed
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