Submarine Slides Research Articles

Geomorphological characteristics and variability of Holocene mass-transport complexes, St. Lawrence River Estuary, Canada

Recently acquired multibeam bathymetry data are used to investigate seafloor instability features along a 310km-long segment of the St. Lawrence River Estuary. The analysis of this dataset indicates that submarine slides occur over a much larger area than previously recognized and that Holocene sediments are reworked by mass-transport along significant portions of both the northwest and southeast margins of the Laurentian Channel. In the surveyed area, 96 individual mass-transport complexes (MTCs) were identified representing 13% of the seabed. MTCs vary in area from less than 1km2 to more than 40km2 and exhibit various geomorphological signatures. Qualitative observation reveals an apparent disparity between MTCs that remain coherent and those that disintegrate during downslope transport evolving into a blocky morphological signature. For all MTCs, morphological parameters have been measured (area, length, and height) or calculated (slope and roughness). This quantitative analysis provides a unique opportunity to study these parameters in a statistically significant and homogeneous dataset located in a relatively small area that experienced a similar Quaternary history.In many cases, mass transport events appear to initiate in the vicinity of steep bedrock walls located along some segments of the estuary. The timing of mass-transport events was not constrained during this study. However, the fact that the region hosts the Charlevoix seismic zone, the most tectonically active area in eastern Canada, strongly suggests that earthquakes acted as a trigger for submarine landsliding.

The destructive 1946 Unimak near‐field tsunami: New evidence for a submarine slide source from reprocessed marine geophysical data

AbstractThe Mw 8.6 earthquake in 1946 off the Pacific shore of Unimak Island at the end of the Alaska Peninsula generated a far‐field tsunami that crossed the Pacific to Antarctica. Its tsunami magnitude, 9.3, is comparable to the 9.1 magnitude of the 2011 Tohoku tsunami. On Unimak Island's Pacific shore, a runup of 42 m destroyed the lighthouse at Scotch Cap. Elsewhere, localized tsunamis with such high runups have been interpreted as caused by large submarine landslides. However, previous to this study, no landslide large enough to generate this runup was found in the area that is limited by the time interval between earthquake shaking and tsunami inundation at Scotch Cap. Reworking of a seismic reflection transect and colocated multibeam bathymetric surveys reveal a landslide block that may explain the 1946 high runup. It is seaward of Scotch Cap on the midslope terrace and within the time‐limited area.

An Indian Ocean tsunami triggered remotely by an onshore earthquake in Balochistan, Pakistan

This paper describes and documents instrumentally recorded tsunami waves that are interpreted as secondary effects of a 7.7 magnitude earthquake in southern Pakistan on 24 September 2013. The tsunami waves were almost unnoticed because the wave heights were low and the tsunami occurred at low tide. The historical record of tsunami events within the Arabian Sea (northern Indian Ocean) is fragmentary. Large tsunamigenic earthquakes are known to be generated in the Makran subduction zone, the area that forms the boundary of the Arabian and Eurasian plates. Submarine sliding is reported along the Owen Fracture Zone, which marks the boundary between the Arabian and Indian plates. Hence, the tsunami hazard potential within the Arabian Sea is enigmatic. Our analysis is based on sea-level oscillations recorded at various tide-gauge stations along the coastlines of Oman, Pakistan, and Iran, as well as eyewitness accounts of the event in Oman. Our results indicate that the waves were in the range of 1 m or less in height. They were first recorded along the eastern coast of Oman, and propagated toward the west. We suggest that the waves must have been triggered by a submarine slide on the Makran margin. Cascading effects resulting in large submarine slope failures within the Arabian Sea are more frequent than postulated. The hazard potential is underestimated, as such secondary effects of distant ruptures onshore were previously not taken into account.

How does multiscale modelling and inclusion of realistic palaeobathymetry affect numerical simulation of the Storegga Slide tsunami?

The ∼8.15ka Storegga submarine slide was a large (∼3000km3), tsunamigenic slide off the coast of Norway. The resulting tsunami had run-up heights of around 10–20m on the Norwegian coast, over 12m in Shetland, 3–6m on the Scottish mainland coast and reached as far as Greenland. Accurate numerical simulations of Storegga require high spatial resolution near the coasts, particularly near tsunami run-up observations, and also in the slide region. However, as the computational domain must span the whole of the Norwegian-Greenland sea, employing uniformly high spatial resolution is computationally prohibitive. To overcome this problem, we present a multiscale numerical model of the Storegga slide-generated tsunami where spatial resolution varies from 500m to 50km across the entire Norwegian-Greenland sea domain to optimally resolve the slide region, important coastlines and bathymetric changes. We compare results from our multiscale model to previous results using constant-resolution models and show that accounting for changes in bathymetry since 8.15ka, neglected in previous numerical studies of the Storegga slide-tsunami, improves the agreement between the model and inferred run-up heights in specific locations, especially in the Shetlands, where maximum run-up height increased from 8m (modern bathymetry) to 13m (palaeobathymetry). By tracking the Storegga tsunami as far south as the southern North sea, we also found that wave heights were high enough to inundate Doggerland, an island in the southern North Sea prior to sea level rise over the last 8ka.

Generation, Propagation, Run-Up and Impact of Landslide Triggered Tsunami: A Literature Review

Submarine landslide is the most serious threat on both local and regional scales. Tsunami phenomenon induced by submarine slide has put us on the challenge in understanding from generation mechanism to propagation and coastal inundation and mitigating the risk from it. Submarine slides can trigger tsunamis with high run-up affecting offshore structures, subsea facilities and human lives along the shoreline. Unfortunately, there are no effective numerical models that could simulate simultaneously all stages of generation, propagation and run-up of tsunamis phenomena. This paper presents a comprehensive review on the landslide tsunami phenomenon.

Computational Aspects of Submarine Slide Generated Tsunami

Submarine landslide is the most serious threat on both local and regional scales. Tsunami phenomenon induced by submarine slide has put us on the challenge in understanding from generation mechanism to propagation and coastal inundation and mitigating the risk from submarine slide generated tsunami. This research presents the numerical simulation methodology by Smooth Particle Hydrodynamics (SPH) to investigate the impact forces of tsunami waves with the aid of physical modeling. By using parallelSPHysics, it is a source code based on the SPH method to model nearly‐incompressible flows, including various physical processes. The conclusions may potentially be taken as guideline of mitigate the risk from tsunami wave.

Architecture and development of a multi-stage Baiyun submarine slide complex in the Pearl River Canyon, northern South China Sea

The Baiyun submarine slide complex (BSSC) along the Pearl River Canyon of the northern South China Sea has been imaged by multibeam bathymetry and 2D/3D seismic data. By means of maximum likelihood classification with slope aspect and gradient as inputs, the BSSC is subdivided into four domains, denoted as slide area I, II, III and IV. Slide area I is surrounded by cliffs on three sides and has been intensely reshaped by turbidity currents generated by other kinds of mass movement outside the area; slide area II incorporates a shield volcano with a diameter of approximately 10 km and unconfined slides possibly resulting from the toe collapse of inter-canyon ridges; slide area III is dominated by repeated slides that mainly originated from cliffs constituting the eastern boundary of the BSSC; slide area IV is distinguished by a conical seamount with a diameter of 6.5 km and a height of 375 m, and two slides probably having a common source that are separated from each other by a suite of residual strata. The BSSC is interpreted to be composed of numerous slide events, which occurred in the period from 10.5 to 5.5 Ma BP. Six specific factors may have contributed to the development of the BSSC, i.e., gas hydrate dissociation, gas-bearing sediments, submarine volcanic activity, seismicity, sedimentation rate and seafloor geomorphology. A 2D conceptual geological model combining these factors is proposed as a plausible mechanism explaining the formation of the BSSC. However, the BSSC may also have been affected by the Dongsha event (10 Ma BP) as an overriding factor.

Acoustic evidence of a submarine slide in the deepest part of the Arctic, the Molloy Hole

The western Svalbard continental margin contains thick sediment sequences with areas known to contain gas hydrates. Together with a dynamic tectonic environment, this makes the region prone to subm ...

Strength properties of ultra-soft kaolin

Geotechnical design considerations for offshore pipelines, foundations, and submarine slides involve assessment of the strength of fine-grained soils and the degradation of that strength with disturbance and remoulding. For offshore pipelines and slides, the relevant strength may be very low (a few kilopascals or lower), relating to near-surface soils and high levels of remoulding including the entrainment of additional water. It is commonly acknowledged that soils exhibit a loss of strength when disturbed, but it is not clear how the degradation properties vary with liquidity index. To address this uncertainty, this paper describes a series of centrifuge tests on kaolin samples consolidated from slurries with an initial voids ratio of 4.0. A total of 81 cyclic T-bar tests were conducted in samples with shear strengths ranging from 0.08 to 1.7 kPa (reflecting different stages of consolidation and in situ total stresses). Large-strain consolidation numerical analyses were used to assist the interpretation of the T-bar test results. The results demonstrate that the soil ductility (a parameter controlling the rate of strength degradation) can be linearly correlated to the liquidity index. The proposed ductility–liquidity index correlation is subsequently coupled with a previously published sensitivity–liquidity index relationship for natural clays to establish a model for the strain-softening behaviour observed in a T-bar test as a function of consolidation. In turn, because the sensitivity is a function of the liquidity index, the intact soil strength is linked to the remoulded strength obtained from laboratory (e.g., fall cone or miniature vane test) and simple index tests. These provide an improved basis to characterize softening effects for inclusion in simulations of submarine slide runout and models for soil–structure interactions that involve intense remoulding.

Centrifuge modelling of active slide–pipeline loading in soft clay

Submarine slides are a significant hazard to the safe operation of pipelines in the proximity of continental slopes. This paper describes the results of a centrifuge testing programme aimed at studying the impact forces exerted by a submarine slide on an offshore pipeline. This was achieved by dragging a model pipe at varying velocities through fine-grained soil at various degrees of consolidation, hence exhibiting properties spanning from the fluid to the geotechnical domains, relevant to the state of submarine slide material. To simulate the high strain rates experienced by the soil while flowing around a pipe in the path of a submarine slide, tests were conducted at pipe–soil velocities of up to 4·2 m/s. The changing density and shear strength of the samples were back-calculated from T-bar penetrometer test results. A hybrid approach combining geotechnical and fluid-mechanics-based components of horizontal drag resistance was developed. This approach provides an improved method to link the density and strength of the slide material to the force applied on the pipe. Besides fitting the present observations, the method provides an improved reinterpretation of similar data from the literature.

Large-scale submarine landslides, channel and gully systems on the southern Weddell Sea margin, Antarctica

New multibeam bathymetric data from the southeastern Weddell Sea show significant differences in surface morphology of the outer continental shelf and slope between two adjacent cross-shelf troughs. These are the Filchner Trough and a smaller trough to the east which we refer to as the ‘Halley Trough’. Multibeam bathymetric data, acoustic sub-bottom profiler and seismic data show major differences in the incidence and morphologies of submarine gullies, channel systems, submarine slides and iceberg scours, and in sediment deposition. These large-scale differences suggest significant variation in slope and sedimentary processes and in the environmental setting between the two troughs, leading to much greater deposition at the mouth of the Filchner Trough. Bedforms, including a terminal moraine and scalloped embayments on the outer shelf of the Halley Trough, provide insight into the relative timing and extent of past ice-sheet grounding and point to grounded ice near to the shelf edge during the Late Quaternary. The new data reveal two large-scale submarine slides on the upper slope of the eastern Crary Fan, a trough mouth fan offshore from the Filchner Trough. Both slides head at the shelf edge (~ 500 m water depth), with the largest slide measuring 20 km wide and with an incision depth of 60 m. Multibeam and seismic data show elongate slabs on the seafloor surface of the mid-slope. The lack of a discernible sedimentary cover suggests that they were generated after the Last Glacial Maximum (LGM). This is unusual because post-LGM submarine slides are very rare on the Antarctic continental margin, and to our knowledge, no other post-LGM slides have been documented on an Antarctic trough mouth fan. Because the slides occur on a part of the continental slope where the deposition of glacial debris was greatest, we speculate that weaker, unconsolidated sedimentary layers within the subsurface are important for slide initiation here.

Sea level rise and submarine mass failures on open continental margins

Submarine mass failures (which include submarine slides or submarine landslides) occur widely on open continental margins. Understanding their cause is of great importance in view of the danger that they can pose both to coastal populations through tsunamis and to the exploitation of ocean floor resources through mass movement of the sea floor. Present knowledge of the causes of submarine mass failures is briefly reviewed, focussing on the role of sea level rise, a process which has previously only infrequently been cited as a cause. It is argued that sea level rise could easily have been involved in at least some of these events by contributing to increased overpressure in sediments of the continental margin whilst causing seismic activity. The Holocene Storegga Slide off South West Norway may have been partly caused by the early Holocene sea level rise in the area, accentuated by meltwater flux from the discharges of Lake Agassiz–Ojibway in North America. Relative sea level rise increased water loading on the Norwegian continental margin, increasing overpressure in the sediments and also causing seismic activity, triggering the Holocene Storegga Slide. Given that some forecasts of future sea level rise are not greatly different from rises which obtained during the early Holocene, the implications of rising sea levels for submarine mass failures in a global warming world are considered.

Submarine Slope Stability Evaluation Based on Strength Reduction Finite Element Method

Submarine landslide can destroy various engineering facilities. So, submarine slope stability evaluation is not only an important link of the construction safety guarantee and soil mechanics in the new field of ocean direction, but also the development of energy demand. Based on the finite element software Abaqus, the strength reduction method has been introduced to submarine slope stability evaluation. With the same finite element model, the safety factors of the land slope and submarine slope are respectively 1.82, 1.83, and 1.205, 1.215, using two criterions such as run-through of plastic zone and run-through of the equivalent plastic strain zone. The studies show that the submarine slide has the following characteristics: the displacement is 5~10 times larger than that of landslide; the obvious " uplift " and " collapse " phenomenon appears near the slope toe and the top of slope; the slide region is much more wider, deeper, less clearly slip shear zone boundary.

New insights into slide processes and seafloor geology revealed by side-scan imagery of the massive Hinlopen Slide, Arctic Ocean margin

The submarine Hinlopen Slide, located along the Arctic Ocean margin, is one of the largest known mass movements on Earth. The slide scar has several unusual morphometric characteristics, including headwalls up to 1,500 m high and spectacularly large, steep-sided rafted megablocks. The slide processes and continental margin properties that produced these features are not well known. A new high-resolution TOBI (towed ocean bottom instrument) side-scan sonar dataset reveals information about the detailed seafloor morphology and, therefore, slide dynamics during the final stages of sliding. First, the headwall area was efficiently and almost completely evacuated of slide debris, which is unusual for large submarine slides. Second, features relating to the propagation of extension to the shelf behind the headwall are absent, suggesting “strong” cohesive shelf material here or that a very stable shelf configuration was reached, possibly defined by NE-SW-trending faults. Third, there is little evidence for the translation of shelf material, again uncommon for submarine slides. Taken together with the occurrence of massive megablocks in the slide debris, Hinlopen Slide is distinct because of the juxtaposition of apparently “stronger” shelf material that has remained intact (headwalls, megablocks), and “weaker” shelf material that disaggregated fully during slope failure. Nevertheless, there is sonograph evidence of variable post-slide disintegration of the megablocks. Contrary to previous interpretations, this suggests that the blocks comprise sedimentary lithologies that are prone to failure, a key aspect awaiting confirmation.

Constraining the characteristics of tsunami waves from deformable submarine slides

As a marine hazard, submarine slope failures have the potential to directly destroy offshore infrastructure, and, if a tsunami is generated, it also endangers the life of those who live and work at the coastline. The hazard and risk from tsunamis generated by submarine mass failure is difficult to quantify and evaluate due to the problems to constrain the characteristics of the triggered submarine landslide, which introduces unquantifiable uncertainty to hazard assessments based on numerical modelling. To lower the uncertainty, we present a method that determines material parameters for the slide body to constrain the generated tsunami waves. Our method employs the distribution of landslide run-out masses and their comparison with simulations. It assumes that the slide material can be approximated by bulk values during the slide motion. To demonstrate our method, we make use of Valdes slide run-out masses off the Chilean coast

Experimental studies of the flow-front and drag forces exerted by subaqueous mudflow on inclined base

Submarine slides are one of the most complex geotechnical problems causing serious damages to the seabed environment. Damages may lead to imminent destruction of offshore facilities such as platform and subsea pipeline. Mud sediment was the most susceptible of subsea material involved in the event. The completeness of field investigation is very limited; therefore, laboratory experiment is implemented in view of modeling the dynamics movement at the time of submarine slides occurs. The current experiment was conducted by generating the mudflow in water ambient over an inclined base to observe the flow-front structures of the mudflow. As facility to investigate the drag force exerted by mudflow, additional pipe model was positioned at certain flow distance. Mud models were prepared from mixtures of 10–35 % by weight of kaolin and water. Mudflow observations were limited to 3.5-m run-out distance with an exemption for 35 % KCC since this percentage stopped flow at 2.3-m flow distance. The role analysis of destructive flow was developed by the determination of drag force coefficient exerted by mudflow incorporating the Reynolds number. Velocity analysis indicates that all flows were defined as initial flow since they have only one phase of slumping phase. With respect to head-flow height and densimetric Froude number, the general form of velocity propagation formula provided the satisfactorily results in tracing mudflow velocity observation of laboratory experiment. Furthermore, the higher percentage of KCC exerted the higher drag force than the lower one.

Stability of submarine slopes in the northern South China Sea: a numerical approach

Submarine landslides occur frequently on most continental margins. They are effective mechanisms of sediment transfer but also a geological hazard to seafloor installations. In this paper, submarine slope stability is evaluated using a 2D limit equilibrium method. Considerations of slope, sediment, and triggering force on the factor of safety (FOS) were calculated in drained and undrained (I broken vertical bar=0) cases. Results show that submarine slopes are stable when the slope is 13A degrees with earthquake peak ground acceleration (PGA) of 0.5 g; whereas with a weak layer, a PGA of 0.2 g could trigger instability at slopes > 10A degrees, and > 3A degrees for PGA of 0.5 g. The northern slope of the South China Sea is geomorphologically stable under static conditions. However, because of the possibility of high PGA at the eastern margin of the South China Sea, submarine slides are likely on the Taiwan Bank slope and eastern part of the Dongsha slope. Therefore, submarine slides recognized in seismic profiles on the Taiwan Bank slope would be triggered by an earthquake, the most important factor for triggering submarine slides on the northern slope of the South China Sea. Considering the distribution of PGA, we consider the northern slope of the South China Sea to be stable, excluding the Taiwan Bank slope, which is tectonically active.

Gravity flow and submarine slide deposits in the Miocene Ushikiri Formation, Eastern Shimane, Japan

Gravity flow and submarine slide deposits in the Miocene Ushikiri Formation, Eastern Shimane, Japan

Reevaluation of the Piermont-Frontenac allochthon in the Upper Connecticut Valley: Restoration of a coherent Boundary Mountains-Bronson Hill stratigraphic sequence

The regional extent and mode and time of emplacement of the Piermont-Frontenac allochthon in the Boundary Mountains–Bronson Hill anticlinorium of the Upper Connecticut Valley, New Hampshire–Vermont, are controversial. Moench and coworkers beginning in the 1980s proposed that much of the autochthonous pre–Middle Ordovician section of the anticlinorium was a large allochthon of Silurian to Early Devonian rocks correlated to those near Rangeley, Maine. This ∼200-km-long allochthon was postulated to have been transported westward in the latest Silurian to Early Devonian as a soft-sediment gravity slide on a hypothesized Foster Hill fault. New mapping and U-Pb geochronology do not support this interpretation. The undisputed Rangeley sequence in the Bean Brook slice is different from the disputed sequence in the proposed larger Piermont-Frontenac allochthon, and field evidence for the Foster Hill fault is lacking. At the type locality on Foster Hill, the postulated “fault” is a stratigraphic contact within the Ordovician Ammonoosuc Volcanics. The proposed Foster Hill fault would place the Piermont-Frontenac allochthon over the inverted limb of the Cornish(?) nappe, which includes the Emsian Littleton Formation, thus limiting the alleged submarine slide to post-Emsian time. Mafic dikes of the 419 Ma Comerford Intrusive Complex intrude previously folded strata attributed to the larger Piermont-Frontenac allochthon as well as the autochthonous Albee Formation and Ammonoosuc Volcanics. The Lost Nation pluton intruded and produced hornfels in previously deformed Albee strata. Zircons from an apophysis of the pluton in the hornfels have a thermal ionization mass spectrometry 207 Pb/ 206 Pb age of 444.1 ± 2.1 Ma. Tonalite near Bath, New Hampshire, has a zircon sensitive high-resolution ion microprobe 206 Pb/ 238 U age of 492.5 ± 7.8 Ma. The tonalite intrudes the Albee Formation, formerly interpreted as the Silurian Perry Mountain Formation of the proposed allochthon. Collectively, these features indicate that the large Piermont-Frontenac allochthon gravity slide of Silurian-Devonian strata, as previously proposed, cannot exist. Allochthonous rocks are restricted to a 25 km 2 klippe, the Bean Brook slice, emplaced by hard-rock thrusting in the post-Emsian Devonian. The Albee Formation, the oldest unit in the study area, is older than the Late Cambrian tonalite at Bath. The correlation and apparent continuity along strike to the northeast of the Albee Formation with the Dead River Formation suggest that the Albee Formation, like the Dead River Formation, is of Ganderian affinity and that the Bronson Hill magmatic arc in the Upper Connecticut Valley was built on Ganderian crust. The Dead River Formation is unconformably overlain by Middle and Upper Ordovician volcanic units; the unconformity is attributed to the pre-Arenig Penobscottian orogeny. Some of the pre-Silurian deformation in the Upper Connecticut Valley may be Penobscottian rather than Taconian. New stratigraphic units defined herein include the pelitic Scarritt Member of the Albee Formation, the Ordovician Washburn Brook Formation consisting of synsedimentary breccia and coticule, chert, and ironstone, and the Devonian–Silurian Sawyer Mountain Formation, probably correlative with the Frontenac Formation. The Partridge Formation is partially coeval with the Ammonoosuc Volcanics.

Catastrophic fluid escape venting-tunnels and related features associated with large submarine slides on the continental rise off Vesterålen–Troms, North Norway

Video inspection of the seabed on the continental rise (ca. 2200 m water depth) off Vesterålen–Troms, North Norway has revealed several remarkable features, including large tunnels, small tunnels, chimney tunnels, carbonate crusts and bacterial mats. The structures occur in landslide areas with slide blocks up to 2 km long, 1 km wide and 100 m high. We hypothesize that the large seabed tunnels, in and between slide blocks and with opening diameters up to 1 m and apparent inner diameters of 10–20 cm, are formed by dewatering of fine-grained sediments buried by the slide masses and possibly venting of underground gas reservoirs related to sliding and loading. This process probably occurred instantaneously after sliding. Numerous small tunnels with diameters up to a few centimetres, in slide blocks of compacted sediments, may have formed by dewatering following sudden pressure release or by decomposition of gas hydrates following off-loading of sediments due to sliding. Bacterial mats and carbonate crusts indicate active leakage of subsurface fluids and methane through the seabed and the gas hydrate stability zone, either from thermogenic sources or from shallow reservoirs. Cemented chimney tunnels up to 15 cm tall, and with inner diameters up to a few centimetres occur both on slide blocks and on flat and even seabed. The presence of apparently both inactive and active chimney tunnels indicates that gas and fluid release is a process that has been periodically active, possibly from before sliding up to the present.