Influence of Salt Tectonics On Fault Displacements and Submarine Slope Failures from Algeria To Sardinia

2019 ◽  
Vol 25 (4) ◽  
pp. 318-330 ◽  
Author(s):  
Julia A. Yeakley ◽  
Abdul Shakoor ◽  
William Johnson
Keyword(s):  
Debris Flows ◽  
Average Rate ◽  
Plate Boundary ◽  
Western Mediterranean ◽  
Turbidity Currents ◽  
Salt Tectonics ◽  
Slope Failures ◽  
Submarine Slope ◽  
Lateral Extent ◽  
Pipeline Route

ABSTRACT We used previously obtained marine geophysical and geotechnical data for the proposed Galsi pipeline route from Algeria to Sardinia to analyze the buried salt distribution, rates of fault displacements, and frequency and lateral extent of submarine slope failures. Crossing the convergent African/Nubian–European plate boundary, the southern section of the pipeline route traverses continental shelves and slopes of Algeria and Sardinia as well as the Algerian abyssal plain of the western Mediterranean. Deeply buried Messinian-aged salt is present throughout this area. Being less dense and more buoyant than the overburden sediment, the salt tends to flow upward to form diapiric structures that, in turn, result in the formation of faults and landslides in the overlying sediment. Measured offsets from seismic profiles of different resolutions were compared with predicted sediment age at depth of each offset, yielding an average rate of fault displacement of 1.5 cm/kiloyear (ky). The highest rates of displacement are along the Cagliari slope near Sardinia (2.5-2.7 cm/ky) and near the convergent plate boundary (2.3 cm/ky). Utilizing the same geophysical data, the frequency and lateral extent of submarine slope failures in the study area can also be linked to the distribution of salt and the influence of salt tectonics. Turbidity currents and hyperpycnal flows are present within the Algerian basin, whereas local debris flows, landslide runouts, and channelized debris flows are present along the Sardinian slope. The low sedimentation rates, determined in this study, suggest that the most recent slope failures related to salt tectonics occurred more than 12,000 years ago.

Investigating the controls of submarine landslides and associated hazards in Pangnirtung Fiord, Eastern Baffin Island (Nunavut)

2021 ◽  
Author(s):  
Philip Sedore ◽  
Alexandre Normandeau ◽  
Vittorio Maselli
Keyword(s):  
High Latitude ◽  
Debris Flows ◽  
Slope Failure ◽  
Recurrence Time ◽  
High Recurrence Rate ◽  
Baffin Island ◽  
Submarine Landslides ◽  
Slope Failures ◽  
Near Surface ◽  
Submarine Slope

<p>High-latitude fiords are susceptible to hazardous subaerial and submarine slope failures. Recent investigations have shown that past slope failures in fiords of Greenland and Alaska have generated devastating landslide induced tsunamis. Since coastal communities inhabit these high-latitude fiords, it is critical to understand the slope failure recurrence time, their distribution, potential triggers, and ability to generate tsunamis. In this study, we identified > 50 near-surface submarine landslides in Pangnirtung Fiord, eastern Baffin Island, Nunavut, using multibeam bathymetric and sub-bottom profiler data, along with sediment gravity-cores collected in 2019. Morphometric and morphological analyses, along with sedimentological analyses, were carried out on submarine landslide deposits to quantify their spatial and temporal distribution throughout the fiord and to evaluate the factors that may have triggered the slope failures.</p><p>Combining bathymetric with topographic data from unmanned aerial vehicle imagery, we found that most of these landslide deposits are relatively small (~ 0.08 km<sup>2</sup>) and are associated with outwash fans and steep fiord sidewalls. However, since most slope failure head scarps lie between the intertidal zone and ~30 m water depth, they could not be mapped, which makes it challenging to determine the triggers of the submarine slope failures. Radiocarbon dating reveals that most of these surficial landslide deposits are younger than 500 years old and that they were most likely triggered at different times. This finding highlights a high recurrence rate of slope failures within the fiord, suggesting that localised triggers are responsible for slope failures within the fiord, as opposed to widespread, seismically induced triggers which do not occur as frequently in the study area. In addition, the elongated morphology of the landslide deposits and the varying degrees of landslide deposit surface roughness supports localised point-source triggers. Since most landslides are associated with subaerial outwash fans and deltas, we suggest that triggers of these relatively frequent submarine landslides within Pangnirtung Fiord include rapid floodwater input, subaerial debris flows, and sea-ice loading during low tide.</p><p>This research shows that slope failures in a high-latitude fiord are affected by the interaction of numerous subaerial and submarine processes, leading us to speculate that a potential increase in the frequency of subaerial debris flows and river floods due to climate change may increase the recurrence of submarine landslides.<strong> </strong></p>

scholarly journals On the potential of gassy marine soils triggering submarine slope instabilities

2020 ◽  
Vol 205 ◽  
pp. 12006
Author(s):  
Pauline Kaminski ◽  
Jürgen Grabe
Keyword(s):  
Slope Failure ◽  
Turbidity Currents ◽  
Continental Margins ◽  
Extensive Literature ◽  
Slope Failures ◽  
Free Gas ◽  
Submarine Slope ◽  
Failure Event ◽  
Liquefaction Failure ◽  
Excess Pore Pressures

The development of debris flows and turbidity currents in the course of a submarine slope failure event can cause major damage in offshore infrastructure. Additionally, the tsunamogenic potential of large slope failures at continental margins poses a direct threat to coastal communities. Therefore, the trigger mechanisms of submarine slope failures have been thoroughly investigated in the past. However, the influence of free gas in the sediment, which has been observed close to several slide events, remains unexplained. In order to evaluate the potential of gassy marine soils to precondition or trigger slope failure the mechanical behaviour of gassy soils is assessed based on an extensive literature review. It is found that gas-induced excess pore pressures can lead to liquefaction failure in sands, while cohesive, gassy soils show a less conclusive response. Hence, fine-grained soils and approaches to implement the gas impact into relevant existing constitutive soil models are assessed in greater detail. Concludingly, based on the predominant boundary conditions in failure prone regions at the continental margins, free gas occurrence can be defined as a preconditioning factor rather than as a definite trigger mechanism.

Slope failures along the deformation front of the Cascadia margin: linking slide morphology to subduction zone parameters

2018 ◽  
Vol 477 (1) ◽  
pp. 47-67 ◽  
Author(s):  
Michael Riedel ◽  
Michelle M. Côté ◽  
Morelia Urlaub ◽  
Jacob Geersen ◽  
Nastasja A. Scholz ◽  
...  
Keyword(s):  
Debris Flows ◽  
Slope Failure ◽  
Accretionary Prism ◽  
Tsunami Generation ◽  
Slope Failures ◽  
Deformation Front ◽  
Acoustic Data ◽  
Submarine Slope ◽  
Cascadia Margin ◽  
Zone Parameters

AbstractMarine acoustic data are used to map and characterize submarine slope failure along the accretionary prism of Cascadia. Two main styles of slope failure are identified: (1) failures with curved head scarps, which are predominantly associated with incoherent debris-flow deposits; and (2) failures with rectangular head scarps, which are predominantly associated with intact sediment blocks. Rectangular head scarps mostly occur on thrust ridges with slope angles <16° and ridge heights <650 m, whereas curved head scarps occur predominantly on steeper and higher ridges. Off Vancouver Island, failure style and head-scarp geometry also change with ridge azimuth. We propose that the curved head scarps and debris flows may be a result of higher kinetic forcing of the downsliding sediments and a higher degree of mixing. At the more gently sloped, less elevated ridges, the kinetic forcing may be smaller, which leads to intact failure masses. Extensional faults at ridges with curved scarps may result from oversteepening and collapse of the sediments that cannot withstand their own weight due to limited internal shear strength. The slide geometries and potential controls on failure style may inform subsequent studies in assessing the risks for tsunami generation from submarine slope failures along the Cascadia margin.

Japanese early-warning for debris flows and slope failures using rainfall indices with Radial Basis Function Network

Landslides ◽  
2010 ◽  
Vol 7 (3) ◽  
pp. 325-338 ◽  
Author(s):  
Nobutomo Osanai ◽  
Takeshi Shimizu ◽  
Kazumasa Kuramoto ◽  
Shinichi Kojima ◽  
Tomoyuki Noro
Keyword(s):  
Radial Basis Function ◽  
Early Warning ◽  
Basis Function ◽  
Debris Flows ◽  
Radial Basis Function Network ◽  
Slope Failures ◽  
Radial Basis ◽  
Function Network

scholarly journals The importance of entrainment and bulking on debris flow runout modeling: examples from the Swiss Alps

2015 ◽  
Vol 15 (11) ◽  
pp. 2569-2583 ◽  
Author(s):  
F. Frank ◽  
B. W. McArdell ◽  
C. Huggel ◽  
A. Vieli
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Data ◽  
Average Rate ◽  
Hazard Analysis ◽  
Maximum Shear Stress ◽  
Empirical Relationship ◽  
Swiss Alps ◽  
Field Site ◽  
Practical Applications

Abstract. This study describes an investigation of channel-bed entrainment of sediment by debris flows. An entrainment model, developed using field data from debris flows at the Illgraben catchment, Switzerland, was incorporated into the existing RAMMS debris-flow model, which solves the 2-D shallow-water equations for granular flows. In the entrainment model, an empirical relationship between maximum shear stress and measured erosion is used to determine the maximum potential erosion depth. Additionally, the average rate of erosion, measured at the same field site, is used to constrain the erosion rate. The model predicts plausible erosion values in comparison with field data from highly erosive debris flow events at the Spreitgraben torrent channel, Switzerland in 2010, without any adjustment to the coefficients in the entrainment model. We find that by including bulking due to entrainment (e.g., by channel erosion) in runout models a more realistic flow pattern is produced than in simulations where entrainment is not included. In detail, simulations without entrainment show more lateral outflow from the channel where it has not been observed in the field. Therefore the entrainment model may be especially useful for practical applications such as hazard analysis and mapping, as well as scientific case studies of erosive debris flows.

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