Search

Multiple styles of failure, ranging from densely spaced, mass transport driven canyons to the large, slab-type slope failure of the Currituck Slide, characterize adjacent sections of the central U.S. Atlantic margin that appear to be defined by variations in geologic framework. Here we use regionally extensive, deep penetration multichannel seismic (MCS) profiles to reconstruct the influence of the antecedent margin physiography on sediment accumulation along the central U.S. Atlantic continental shelf-edge, slope, and uppermost rise from the Miocene to Present. These data are combined with high-resolution sparker MCS reflection profiles and multibeam bathymetry data across the Currituck Slide Complex. Pre-Neogene allostratigraphic horizons beneath the slope are generally characterized by low gradients and convex downslope profiles. This is followed by the development of thick, prograded deltaic clinoforms during the middle Miocene. Along-strike variations in morphology of a regional unconformity at the top of this middle Miocene unit appear to have set the stage for differing styles of mass transport along the margin. Areas north and south of the Currituck Slide are characterized by oblique margin morphology, defined by an angular shelf-edge and a relatively steep (> 8°), concave slope profile. Upper slope sediment bypass, closely spaced submarine canyons, and small, localized landslides confined to canyon heads and sidewalls characterize these sectors of the margin. In contrast, the Currituck region is defined by a sigmoidal geometry, with a rounded shelf-edge rollover and gentler slope gradient ( 800 m), regionally continuous stratified slope deposits suggest the low gradient Currituck region was a primary depocenter for fluvial inputs during multiple sea level lowstands. These results imply that the rounded, gentle slope physiography developed during the middle Miocene allowed for a relatively high rate of subsequent sediment accumulation, thus providing a mechanism for compaction–induced overpressure that preconditioned the Currituck region for failure. Detailed examination of the regional geological framework illustrates the importance of both sediment supply and antecedent slope physiography in the development of large, potentially unstable depocenters along passive margins.

Submarine landslides occurring along the margins of the Gulf of Mexico (GOM) represent a low-likelihood, but potentially damaging source of tsunamis. New multibeam bathymetry coverage reveals that mass wasting is pervasive along the Yucatan Shelf edge with several large composite landslides possibly removing as much as 70 km3 of the Cenozoic sedimentary section in a single event. Using GIS-based analysis, the dimensions of six landslides from the central and northern sections of the Yucatan Shelf/Campeche Escarpment were determined and used as input for preliminary tsunami generation and propagation models. Tsunami modeling is performed to compare the propagation characteristics and distribution of maximum amplitudes throughout the GOM among the different landslide scenarios. Various factors such as landslide geometry, location along the Yucatan Shelf/Campeche Escarpment, and refraction during propagation result in significant variations in the affected part of the Mexican and US Gulf Coasts. In all cases, however, tsunami amplitudes are greatest along the northern Yucatan Peninsula.

Landslides are common in aquatic settings worldwide, from lakes and coastal environments to the deep sea. Fast-moving, large-volume landslides can potentially trigger destructive tsunamis. Landslides damage and disrupt global communication links and other critical marine infrastructure. Landslide deposits act as foci for localized, but important, deep-seafloor biological communities. Under burial, landslide deposits play an important role in a successful petroleum system. While the broad importance of understanding subaqueous landslide processes is evident, a number of important scientific questions have yet to receive the needed attention. Collecting quantitative data is a critical step to addressing questions surrounding subaqueous landslides. Quantitative metrics of subaqueous landslides are routinely recorded, but which ones, and how they are defined, depends on the end-user focus. Differences in focus can inhibit communication of knowledge between communities, and complicate comparative analysis. This study outlines an approach specifically for consistent measurement of subaqueous landslide morphometrics to be used in the design of a broader, global open-source, peer-curated database. Examples from different settings illustrate how the approach can be applied, as well as the difficulties encountered when analysing different landslides and data types. Standardizing data collection for subaqueous landslides should result in more accurate geohazard predictions and resource estimation., peer-reviewed

Submarine canyons are common features of continental margins worldwide. They are conduits that funnel vast quantities of sediment from the continents to the deep sea. Though it is known that submarine canyons form primarily from erosion induced by submarine sediment flows, we currently lack quantitative, empirically based expressions that describe the morphology of submarine canyon networks. Multibeam bathymetry data along the entire passive US Atlantic margin (USAM) and along the active central California margin near Monterey Bay provide an opportunity to examine the fine-scale morphology of 171 slope-sourced canyons. Log–log regression analyses of canyon thalweg gradient ( S ) versus up-canyon catchment area ( A ) are used to examine linkages between morphological domains and the generation and evolution of submarine sediment flows. For example, canyon reaches of the upper continental slope are characterized by steep, linear and/or convex longitudinal profiles, whereas reaches farther down canyon have distinctly concave longitudinal profiles. The transition between these geomorphic domains is inferred to represent the downslope transformation of debris flows into erosive, canyon-flushing turbidity flows. Over geologic timescales this process appears to leave behind a predictable geomorphic fingerprint that is dependent on the catchment area of the canyon head. Catchment area, in turn, may be a proxy for the volume of sediment released during geomorphically significant failures along the upper continental slope. Focused studies of slope-sourced submarine canyons may provide new insights into the relationships between fine-scale canyon morphology and down-canyon changes in sediment flow dynamics.

Submarine landslides occurring along the margins of the Gulf of Mexico (GOM) represent a low-likelihood, but potentially damaging source of tsunamis. New multibeam bathymetry coverage reveals that mass wasting is pervasive along the Yucatan Shelf edge with several large composite landslides possibly removing as much as 70 km3 of the Cenozoic sedimentary section in a single event. Using GIS-based analysis, the dimensions of six landslides from the central and northern sections of the Yucatan Shelf/Campeche Escarpment were determined and used as input for preliminary tsunami generation and propagation models. Tsunami modeling is performed to compare the propagation characteristics and distribution of maximum amplitudes throughout the GOM among the different landslide scenarios. Various factors such as landslide geometry, location along the Yucatan Shelf/Campeche Escarpment, and refraction during propagation result in significant variations in the affected part of the Mexican and US Gulf Coasts. In all cases, however, tsunami amplitudes are greatest along the northern Yucatan Peninsula.

Landslides are often viewed together with other natural hazards, such as earthquakes and fires, as phenomena whose size distribution obeys an inverse power law. Inverse power law distributions are the result of additive avalanche processes, in which the final size cannot be predicted at the onset of the disturbance. Volume and area distributions of submarine landslides along the U.S. Atlantic continental slope follow a lognormal distribution and not an inverse power law. Using Monte Carlo simulations, we generated area distributions of submarine landslides that show a characteristic size and with few smaller and larger areas, which can be described well by a lognormal distribution. To generate these distributions we assumed that the area of slope failure depends on earthquake magnitude, i.e., that failure occurs simultaneously over the area affected by horizontal ground shaking, and does not cascade from nucleating points. Furthermore, the downslope movement of displaced sediments does not entrain significant amounts of additional material. Our simulations fit well the area distribution of landslide sources along the Atlantic continental margin, if we assume that the slope has been subjected to earthquakes of magnitude ≤ 6.3. Regions of submarine landslides, whose area distributions obey inverse power laws, may be controlled by different generation mechanisms, such as the gradual development of fractures in the headwalls of cliffs. The observation of a large number of small subaerial landslides being triggered by a single earthquake is also compatible with the hypothesis that failure occurs simultaneously in many locations within the area affected by ground shaking. Unlike submarine landslides, which are found on large uniformly-dipping slopes, a single large landslide scarp cannot form on land because of the heterogeneous morphology and short slope distances of tectonically-active subaerial regions. However, for a given earthquake magnitude, the total area affected by subaerial landslides is comparable to that calculated by slope stability analysis for submarine landslides. The area distribution of subaerial landslides from a single event may be determined by the size distribution of the morphology of the affected area, not by the initiation process.

article The nearly complete coverage of the U.S. Atlantic continental slope and rise by multibeam bathymetry and backscatter imagery provides an opportunity to reevaluate the distribution of submarine landslides along the margin and reassess the controls on their formation. Landslides can be divided into two categories based on their source areas: those sourced in submarine canyons and those sourced on the open continental slope and rise. Landslide distribution is in part controlled by the Quaternary history of the margin. They cover 33% of the continental slope and rise of the glacially influenced New England margin, 16% of the sea floor offshore of the fluvially dominated Middle Atlantic margin, and 13% of the sea floor south of Cape Hatteras. The headwall scarps of open-slope sourced landslides occur mostly on the lower slope and upper rise while they occur mostly on the upper slope in the canyon-sourced ones. The deposits from both landslide categories are generally thin (mostly 20-40 m thick) and comprised primarily of Quaternary material, but the volumes of the open-slope sourced landslide deposits can be larger (1-392 km 3 ) than the canyon- sourced ones (1-10 km 3 ). The largest failures are located seaward of shelf-edge deltas along the southern New England margin and near salt domes that breach the sea floor south of Cape Hatteras. The spatial distribution of landslides indicates that earthquakes associated with rebound of the glaciated part of the margin or earthquakes associated with salt domes were probably the primary triggering mechanism although other processes may have pre-conditioned sediments for failure. The largest failures and those that have the potential to generate the largest tsunamis are the open-slope sourced landslides. Published by Elsevier B.V.

article i nfo Article history: Accepted 24 September 2008 Tsunami generation fromthe Currituck landslide offshore NorthCarolina and propagation of waves towardthe U.S. coastline are modeled based on recent geotechnical analysis of slide movement. A long and intermediate wave modeling package (COULWAVE) based on the non-linear Boussinesq equations are used to simulate the tsunami. This model includes procedures to incorporate bottom friction, wave breaking, and overland flow during runup. Potential tsunamis generated from the Currituck landslide are analyzed using four approaches: (1) tsunami wave history is calculated from several different scenarios indicated by geotechnical stability and mobility analyses; (2) a sensitivity analysis is conducted to determine the effects of both landslide failure duration during generation and bottom friction along the continental shelf during propagation; (3) wave history is calculated over a regional area to determine the propagation of energy oblique to the slide axis; and (4) a high-resolution 1D model isdeveloped to accuratelymodel wavebreakingand the combined influence of nonlinearity and dispersion during nearshore propagation and runup. The primary source parameter that affects tsunami severity for this case study is landslide volume, with failure duration having a secondary influence. Bottom friction during propagation across the continental shelf has a strong influence on the attenuation of the tsunami during propagation. The high-resolution 1D model also indicates that the tsunami undergoes nonlinear fission prior to wave breaking, generating independent, short-period waves. Wave breaking occurs approximately 40-50 km offshore where a tsunami bore is formed that persists during runup. These analyses illustrate the complex nature of landslide tsunamis, necessitating the use of detailed landslide stability/mobility models and higher-order hydrodynamic models to determine their hazard. Published by Elsevier B.V.

Assessment of the probability for destructive landslide-generated tsunamis depends on the knowledge of the number, size, and frequency of large submarine landslides. This paper investigates the size distribution of submarine landslides along the U.S. Atlantic continental slope and rise using the size of the landslide source regions (landslide failure scars). Landslide scars along the margin identified in a detailed bathymetric Digital Elevation Model (DEM) have areas that range between 0.89 km2 and 2410 km2 and volumes between 0.002 km3 and 179 km3. The area to volume relationship of these failure scars is almost linear (inverse power-law exponent close to 1), suggesting a fairly uniform failure thickness of a few 10s of meters in each event, with only rare, deep excavating landslides. The cumulative volume distribution of the failure scars is very well described by a log–normal distribution rather than by an inverse power-law, the most commonly used distribution for both subaerial and submarine landslides. A log–normal distribution centered on a volume of 0.86 km3 may indicate that landslides preferentially mobilize a moderate amount of material (on the order of 1 km3), rather than large landslides or very small ones. Alternatively, the log–normal distribution may reflect an inverse power law distribution modified by a size-dependent probability of observing landslide scars in the bathymetry data. If the latter is the case, an inverse power-law distribution with an exponent of 1.3 ± 0.3, modified by a size-dependent conditional probability of identifying more failure scars with increasing landslide size, fits the observed size distribution. This exponent value is similar to the predicted exponent of 1.2 ± 0.3 for subaerial landslides in unconsolidated material. Both the log–normal and modified inverse power-law distributions of the observed failure scar volumes suggest that large landslides, which have the greatest potential to generate damaging tsunamis, occur infrequently along the margin.

The submerged carbonate platform north of Puerto Rico terminates in a high (3,000–4,000 m) and in places steep (>45°) slope characterized by numerous landslide scarps including two 30–50 km-wide amphitheater-shaped features. The origin of the steep platform edge and the amphitheaters has been attributed to: (1) catastrophic failure, or (2) localized failures and progressive erosion. Determining which of the two mechanisms has shaped the platform edge is critically important in understanding landslide-generated tsunami hazards in the region. Multibeam bathymetry, seismic reflection profiles, and a suite sediment cores from the Puerto Rico Trench and the slope between the trench and the platform edge were used to test these two hypotheses. Deposits within trench axis and at the base of the slope are predominantly composed of sandy carbonate turbidites and pelagic sediment with inter-fingering of chaotic debris units. Regionally-correlated turbidites within the upper 10 m of the trench sediments were dated between ∼25 and 22 kyrs and ∼18–19 kyrs for the penultimate and most recent events, respectively. Deposits on the slope are laterally discontinuous and vary from thin layers of fragmented carbonate platform material to thick pelagic layers. Large debris blocks or lobes are absent within the near-surface deposits at the trench axis and the base of slope basins. Progressive small-scale scalloping and self-erosion of the carbonate platform and underlying stratigraphy appears to be the most likely mechanism for recent development of the amphitheaters. These smaller scale failures may lead to the generation of tsunamis with local, rather than regional, impact.

A geomorphological analysis of the Veatch slide complex is presented here indicting the presence of at least two major slides presenting different morphological characteristics and involving different type of sediments (in terms of strength and grain size). These slides took place after the erosion of the Veatch Canyon which had been the locus of many bank failures. It is shown that a more refined morphological analysis of similar landslide areas may lead to the definition of a greater number of slides and a greater role of channels both leading to a more complex interpretation on their mobility.

The 1964 Alaska M w 9.2 earthquake triggered numerous submarine slope failures in fjords of southern Alaska. These failures generated local tsunamis, such as at Whittier, where they inundated the town within 4 min of the beginning of shaking. Run-up was up to 32 m, with 13 casualties. We collected new multibeam bathymetry and high-resolution sparker seismic data in Passage Canal, and we examined bathymetry changes before and after the earthquake. The data reveal the debris flow deposit from the 1964 landslides, which covers the western 5 km of the fjord bottom. Individual blocks in the flow are up to 145-m wide and 25-m tall. Bathymetry changes show the mass transfer deposits originated from the fjord head and Whittier Creek deltas and had a volume of about 42 million m3. The 1964 deposit has an average thickness of ∼5.4 m. Beyond the debris flow, the failures likely deposited a ∼4.6-m thick megaturbidite in a distal basin. We have studied the 1964 submarine landslides in three fjords. All involved failure of the fjord-head delta. All failures eroded basin-floor sediments and incorporated them as they travelled. All the failures deposited blocks, but their size and travel distances varied greatly. We find a correlation between maximum block size and maximum tsunami run-up regardless of the volume of the slides. Lastly, the fjord’s margins were influenced by increased supply of glacial sediments during the little ice age, which along with a long interseismic interval (∼900 years) may have caused the 1964 earthquake to produce particularly numerous and large submarine landslides.

The Munson-Nygren-Retriever (MNR) landslide complex is a series of distinct submarine landslides located between Nygren and Powell canyons on the Georges Bank lower slope. These landslides were first imaged in 1978 using widely-spaced seismic reflection profiles and were further investigated using continuous coverage GLORIA sidescan imagery collected over the landslide complex in 1987. Recent acquisition of high-resolution multibeam bathymetry across these landslides has provided an unprecedented view of their complex morphology and allows for a more detailed investigation of their evacuation and deposit morphologies and sizes, modes of failure, and relationship to the adjacent sections of the margin, including the identification of an additional landslide within the MNR complex, referred to here as the Pickett slide. The evacuation zone of these landslides covers an area of approximately 1,780 km2. The headwalls of these landslides are at a depth of approximately 1,800 m, with evacuation extending for approximately 60 km downslope to the top of the continental rise. High-relief debris deposits, in the form of blocks and ridges, are present down the length of the majority of the evacuation zones and within the deposition area at the base of the slope. On the continental rise, the deposits from each of the most recent failures of the MNR complex landslides merge with debris from earlier continental slope failures, canyon and along-slope derived deposits, and prominent upper-rise failures.

Recent multibeam surveys along the continental slope and rise off southeast New England has enabled a detailed morphological analysis of the Block composite landslide. This landslide consists of at least three large debris lobes resting on a gradient less than 0.5 °. The slide took place on gradients of between 1 ° and 5 ° in Quaternary sediments likely deposited at the time of low sea level and high sedimentation rates associated with glaciations. The slide debris lobes are very close to each other and cover an area of about 1.125 km2 of the sea floor. With an average thickness of 50 m, the total volume of the deposit is estimated at 36 km3. In some cases, the departure zone appears to be near the crest of the continental slope, at a water depth between 500 and 2,000 m with debris spreading over about 20 km at a depth ranging from 2,500 to 2,600 m. From preliminary analysis, at least one lobe of the Block Composite slide (lobe 2) would require further study to evaluate its tsunamigenic potential.

1.- Submarine Mass Movements and Their Consequences.- Submarine Mass Movements: Triggers, Mechanics, and Geotechnical Properties.- Interplay Between Gas Hydrates and Submarine Slope Failure.- Advanced Dynamic Soil Testing - Introducing the New Marum Dynamic Triaxial Testing Device.- Clustering of Geotechnical Properties of Marine Sediments Through Self-Organizing Maps: An Example from the Zakynthos Canyon-Valley System, Greece.- Identification of Shear Zones and Their Causal Mechanisms Using a Combination of Cone Penetration Tests and Seismic Data in the Eastern Niger Delta.- Mass Wasting Dynamics at the Deeper Slope of the Ligurian Margin (Southern France).- Characterization of Micaceous Sand for Investigation of a Subsea Mass Movement.- Estimating Drag Forces on Suspended and Laid-on-Seafloor Pipelines Caused by Clay-Rich Submarine Debris Flow Impact.- Experimental Investigation of Subaqueous Clay-Rich Debris Flows, Turbidity Generation and Sediment Deposition.- The Kinematics of a Debris Avalanche on the Sumatra Margin.- 3D Numerical Modelling of Submerged and Coastal Landslide Propagation.- Peculiar Morphologies of Subaqueous Landslide Deposits and Their Relationship to Flow Dynamics.- Large Landslides on Passive Continental Margins: Processes, Hypotheses and Outstanding Questions.- Origin of Overpressure and Slope Failure in the Ursa Region, Northern Gulf of Mexico.- History of Pore Pressure Build Up and Slope Instability in Mud-Dominated Sediments of Ursa Basin, Gulf of Mexico Continental Slope.- How Does Fluid Inflow Geometry Control Slope Destabilization?.- Geochemical Evidence for Groundwater-Charging of Slope Sediments: The Nice Airport 1979 Landslide and Tsunami Revisited.- Modeling Slope Instability as Shear Rupture Propagation in a Saturated Porous Medium.- Submarine Mass Movements: Case Studies and Hazard Assessment.- Submarine Mass Transport Within Monterey Canyon: Benthic Disturbance Controls on the Distribution of Chemosynthetic Biological Communities.- Multi-direction Flow in a Mass-Transport Deposit, Santos Basin, Offshore Brazil.- Small-Scale Insights into Seismic-Scale Slumps: A Comparison of Slump Features from the Waitemata Basin, New Zealand, and the More Basin, Off-Shore Norway.- The Block Composite Submarine Landslide, Southern New England Slope, U.S.A.: A Morphological Analysis.- Post-Megaslide Slope Stability North of Svalbard, Arctic Ocean.- Geomorphology of the Talisman Slide (Western slope of Hatton Bank, NE Atlantic Ocean).- Investigations on the Peach 4 Debrite, a Late Pleistocene Mass Movement on the Northwest British Continental Margin.- Redistribution of Sediments by Submarine Landslides on the Eastern Nankai Accretionary Prism.- Mass Wasting at the Easternmost Cyprus Arc, Off Syria, Eastern Mediterranean.- Risk Analysis for Hurricane-Wave Induced Submarine Mudslides.- GIS-Based Assessment of Submarine Mudflow Hazard Offshore of the Mississippi Delta, Gulf of Mexico.- Spatial Analysis of Shallow Slope Instability Incorporating an Engineering Geological Ground Model.- Estimating the Empirical Probability of Submarine Landslide Occurrence.- Constraining Geohazards to the Past: Impact Assessment of Submarine Mass Movements on Seabed Developments.- Evaluating Gas-Generated Pore Pressure with Seismic Reflection Data in a Landslide-Prone Area: An Example from Finneidfjord, Norway.- Historic and Paleo-Submarine Landslide Deposits Imaged Beneath Port Valdez, Alaska: Implications for Tsunami Generation in a Glacial Fiord.- Multibeam Bathymetry Investigations of Mass Movements in Lake Le Bourget (NW Alps, France) Using a Portable Platform.- Morphodynamic and Slope Instability Observations at Wabush Lake, Labrador.- Climate-Induced Turbidity Current Activity in NW-African Canyon Systems.- Submarine Mass Movements in Margin Construction and Economic Significance.- Investigating the Timing, Processes and Deposits of One of the World's Largest Submarine Gravity Flows: The 'Bed 5 Event' Off Northwest Africa.- MTCs of the Brazos-Trinity Slope System Thoughts on the Sequence Stratigraphy of MTCs and Their Possible Roles in Shaping Hydrocarbon Traps.- Southeast Australia: A Cenozoic Continental Margin Dominated by Mass Transport.- A Database on Submarine Landslides of the Mediterranean Sea.- Submarine Landslides Along the Algerian Margin: A Review of Their Occurrence and Potential Link with Tectonic Structures.- Mass-Transport Deposits on the Algerian Margin (Algiers Area): Morphology, Lithology and Sedimentary Processes.- Detailed Analysis of a Submarine Landslide (SAR-27) in the Deep Basin Offshore Algiers (Western Mediterranean).- 3D Seismic Interpretation of Mass Transport Deposits: Implications for Basin Analysis and Geohazard Evaluation.- Slope Instability on the French Guiana Transform Margin from Swath-Bathymetry and 3.5 kHz Echograms.- Megaslides in the Foz do Amazonas Basin, Brazilian Equatorial Margin.- Detached and Shelf-Attached Mass Transport Complexes on the Magdalena Deepwater Fan.- Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits in Texas-Louisiana Intraslope Basins Based on High-Resolution (3.5 kHz) Seismic Facies and Piston Cores.- Upper Cretaceous Mass Transport Systems Above the Wyandot Formation Chalk, Offshore Nova Scotia.- The Significance of Mass-Transport Deposits for the Evolution of a Proglacial Continental Slope.- Submarine Mass Movements and Tsunamis.- Middle to Late Miocene Slope Failure and the Generation of a Regional Unconformity Beneath the Western Scotian Slope, Eastern Canada.- Mass Transport Deposits on the Southwestern Newfoundland Slope.- Mass Transport Events and Their Tsunami Hazard.- Hydrodynamic Modeling of Tsunamis Generated by Submarine Landslides: Generation, Propagation, and Shoreline Impact.- Calculations of Tsunamis from Submarine Landslides.- Experiments on Tsunamis Generated by 3D Granular Landslides.- Distal Turbidites and Tsunamigenic Landslides of Stromboli Volcano (Aeolian Islands, Italy).- Tsunamigenic Risks Associated with Mass Transport Complexes in Offshore Trinidad and Venezuela.- Distribution and Tsunamigenic Potential of Submarine Landslides in the Gulf of Mexico.- A Study of the Tsunami Effects of Two Landslides in the St. Lawrence Estuary.- The Pliocene Shelburne Mass-Movement and Consequent Tsunami, Western Scotian Slope.

The Gulf of Mexico (GOM) is a geologically diverse ocean basin that includes three distinct geologic provinces: a carbonate province, a salt province, and canyon to deep-sea fan province, all of which contain evidence of submarine mass movements. The threat of submarine landslides in the GOM as a generator of near-field damaging tsunamis has not been widely addressed. Submarine landslides in the GOM are considered a potential tsunami hazard because: (1) some dated landslides in the GOM have post-glacial ages and (2) recent seismicity recorded within the GOM. We present a brief review of the distribution and style of submarine landslides that have occurred in the GOM during the Quaternary, followed by preliminary hydrodynamic modeling results of tsunami generation from the East Breaks landslide off Corpus Christie, TX.