scholarly journals Submarine mass wasting and associated tsunami risk offshore western Thailand, Andaman Sea, Indian Ocean

2012 ◽  
Vol 12 (8) ◽  
pp. 2609-2630 ◽  
Author(s):  
J. M. Schwab ◽  
S. Krastel ◽  
M. Grün ◽  
F. Gross ◽  
P. Pananont ◽  
...  
Keyword(s):  
Mass Transport ◽  
Andaman Sea ◽  
Excess Pore Pressure ◽  
Western Slope ◽  
Shelf Area ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Recurrence Rates ◽  
Mass Transport Deposits ◽  
Water Depths

Abstract. 2-D seismic data from the top and the western slope of Mergui Ridge in water depths between 300 and 2200 m off the Thai west coast have been investigated in order to identify mass transport deposits (MTDs) and evaluate the tsunamigenic potential of submarine landslides in this outer shelf area. Based on our newly collected data, 17 mass transport deposits have been identified. Minimum volumes of individual MTDs range between 0.3 km3 and 14 km3. Landslide deposits have been identified in three different settings: (i) stacked MTDs within disturbed and faulted basin sediments at the transition of the East Andaman Basin to the Mergui Ridge; (ii) MTDs within a pile of drift sediments at the basin-ridge transition; and (iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (< 1000 m). Our data indicate that the Mergui Ridge slope area seems to have been generally unstable with repeated occurrence of slide events. We find that the most likely causes for slope instabilities may be the presence of unstable drift sediments, excess pore pressure, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes suggesting a small tsunami potential. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge. Mass-wasting events that may occur in the future at similar locations may trigger tsunamis if they comprise sufficient volumes. Landslide tsunamis, emerging from slope failures in the working area and affecting western Thailand coastal areas therefore cannot be excluded, though the probability is very small compared to the probability of earthquake-triggered tsunamis, arising from the Sunda Trench.

Tectonic and geomorphic controls on the distribution of submarine landslides across active and passive margins, eastern New Zealand

2020 ◽  
Author(s):  
Sally Watson ◽  
Joshu Mountjoy ◽  
Gareth Crutchley
Keyword(s):  
New Zealand ◽  
Mass Transport ◽  
Submarine Landslide ◽  
Sediment Supply ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Active Margin ◽  
Eastern Margin ◽  
Marine Habitats ◽  
Mass Transport Deposits

&lt;p&gt;Submarine landslides occur on continental margins globally and can have devastating consequences for marine habitats, offshore infrastructure and coastal communities due to potential tsunamigenic consequences. Evaluation of the magnitude and distribution of submarine landslides is central to marine and coastal hazard planning. Despite this, there are few studies that comprehensively quantify the occurrence of submarine landslides on a margin-wide scale.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;We present the first margin-wide submarine landslide database along the eastern margin of New Zealand comprising &gt;2200 landslide scars and associated mass-transport deposits. Analysis of submarine landslide distribution reveals 1) locations prone to mass-failure, 2) spatial patterns of landslide scale and occurrence, and 3) the potential preconditioning factors and triggers of mass wasting across different geologic settings.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Submarine landslides are widespread on the eastern margin of New Zealand, occurring in water depths from ~300 m to ~4,000 m. Landslide scars and mass transport deposits are more prevalent, and on average larger, on the active margin, compared the passive margin. We attribute higher concentrations of landslides on the active margin to the prevalence of deforming thrust ridges, related to active margin processes including oversteepening, faulting and seamount subduction. Higher sediment supply on the northernmost active margin is also likely to be a key preconditioning factor resulting in the concentration of large landslides in this region.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;In general, submarine landslide scars are concentrated around canyon systems and close to canyon thalwegs. This suggests that not only does mass wasting play a major role in canyon evolution, but also that slope undercutting in canyons may be a fundamental preconditioning factor for slope failure.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Results of this study offer unique insights into the spatial distribution, magnitude and morphology of submarine landslides across different geologic settings, providing a better understanding of the causative factors for mass wasting in New Zealand and around the world.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Evaluating the sealing potential of young and thin mass-transport deposits: Lake Villarrica, Chile

2019 ◽  
Vol 500 (1) ◽  
pp. 129-146 ◽  
Author(s):  
Jasper Moernaut ◽  
Gauvain Wiemer ◽  
Achim Kopf ◽  
Michael Strasser
Keyword(s):  
Shear Strength ◽  
Mass Transport ◽  
Pore Pressure ◽  
Sediment Cores ◽  
Free Fall ◽  
Undrained Shear Strength ◽  
Excess Pore Pressure ◽  
Minor Role ◽  
Mass Transport Deposits ◽  
Undrained Shear

AbstractSubaqueous mass-transport deposits (MTDs) can be important elements in hydrocarbon systems, forming potential reservoirs or seals. Most research has targeted outcrops or moderately to deeply buried MTDs and, therefore, the petrophysical properties of near-seafloor MTDs, and their influence in the trapping and release of shallow fluids, is poorly studied. Here, we investigate shallow MTDs in Lake Villarrica (Chile) by combining sub-bottom profiles, free-fall penetrometer data, pore pressure dissipation tests and geotechnical properties of sediment cores. Low undrained shear strength under a surficial MTD indicates underconsolidation caused by sudden loading and rapid sealing. Larger, buried MTDs show acoustic signatures of free gas at their base, indicating effective sealing. This is supported by degassing core gaps just below MTDs and by excess pore pressure ratios c. 30–70% within MTDs. Acoustic windows below rafted blocks suggest local fluid escape. MTDs exhibit elevated undrained shear strength and reduced porosity compared to surrounding sediments, but are comparable to upslope source sequences. This suggests that MTD sealing capacity in Villarrica relates to the apparently overconsolidated nature of the slope sequence, leaving a minor role for shear densification. This study shows that shallow MTDs can form a relatively rapid seal for fluid migration, locally degraded by rafted blocks.

scholarly journals Indonesian Throughflow as a preconditioning mechanism for submarine landslides in the Makassar Strait

2020 ◽  
Vol 500 (1) ◽  
pp. 195-217 ◽  
Author(s):  
Rachel E. Brackenridge ◽  
Uisdean Nicholson ◽  
Benyamin Sapiie ◽  
Dorrik Stow ◽  
Dave R. Tappin
Keyword(s):  
Mass Transport ◽  
Conveyor Belt ◽  
Ocean Current ◽  
Indonesian Throughflow ◽  
Submarine Landslides ◽  
Fault Rupture ◽  
The South ◽  
The Pacific ◽  
The Indian Ocean ◽  
Mass Transport Deposits

AbstractThe Makassar Strait is an important oceanic gateway, through which the main branch of the Indonesian Throughflow (ITF) transports water from the Pacific to the Indian Ocean. This study identifies a number of moderate (>10 km3) to giant (up to 650 km3) mass transport deposits within the Makassar North Basin Pleistocene–Recent section. The majority of submarine landslides that formed these deposits originated from the Mahakam pro-delta, with the largest skewed to the south. We see clear evidence for ocean-current erosion, lateral transport and contourite deposition across the upper slope. This suggests that the ITF is acting as an along-slope conveyor belt, transporting sediment to the south of the delta, where rapid sedimentation rates and slope oversteepening results in recurring submarine landslides. A frequency for the >100 km3 failures is tentatively proposed at 0.5 Ma, with smaller events occurring at least every 160 ka. This area is therefore potentially prone to tsunamis generated from these submarine landslides. We identify a disparity between historical fault rupture-triggered tsunamis (located along the Palu-Koro fault zone) and the distribution of mass transport deposits in the subsurface. If these newly identified mass failures are tsunamigenic, they may represent a previously overlooked hazard in the region.

scholarly journals Mass wasting along the NW African continental margin

2018 ◽  
Vol 477 (1) ◽  
pp. 151-167 ◽  
Author(s):  
S. Krastel ◽  
W. Li ◽  
M. Urlaub ◽  
A. Georgiopoulou ◽  
R. B. Wynn ◽  
...  
Keyword(s):  
Continental Margin ◽  
Large Scale ◽  
Current Knowledge ◽  
Special Focus ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Recurrence Rates ◽  
Volcanic Debris ◽  
Rising Sea Level ◽  
Over Time

AbstractThe NW African continental margin is well known for the occurrence of large-scale but infrequent submarine landslides. The aim of this paper is to synthesize the current knowledge on submarine mass wasting off NW Africa with a special focus on the distribution and timing of large landslides. The described area reaches from southern Senegal to the Agadir Canyon. The largest landslides from south to north are the Dakar Slide, the Mauritania Slide, the Cap Blanc Slide, the Sahara Slide and the Agadir Slide. Volumes of individual slides reach several hundreds of cubic kilometres; run-outs are up to 900 km. In addition, giant volcanic debris avalanches are widespread on the flanks of the Canary Islands. All headwall areas are complex with clear indications of multiple failures. The most prominent similarity between all investigated landsides is the existence of widespread glide planes that follow the stratigraphy, which points to weak layers as most important preconditioning factor for the failures. Landslides with volumes larger than 100 m3 are close to being evenly distributed over time, contradicting previous suggestions that landslides off NW Africa occur at periods of low or rising sea level. The risk associated with the landslides off NW Africa, however, is relatively low due to their long recurrence rates.

Formation of excess fluid pressure, sediment fluidization and mass-transport deposits in the Plio-Pleistocene Boso forearc basin, central Japan

2018 ◽  
Vol 477 (1) ◽  
pp. 255-264 ◽  
Author(s):  
Nana Kamiya ◽  
Masayuki Utsunomiya ◽  
Yuzuru Yamamoto ◽  
Junichi Fukuoka ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Mass Transport ◽  
Large Scale ◽  
Fluid Pressure ◽  
High Porosity ◽  
Submarine Landslides ◽  
Forearc Basin ◽  
Central Japan ◽  
Pressure Interval ◽  
The Stability ◽  
Mass Transport Deposits

AbstractAnalyses of consolidation state, fabrics and physical properties were conducted on rock samples from the Plio-Pleistocene Boso forearc basin, central Japan. Consolidation tests identified that the trend in consolidation yield stress was systematically 8 MPa smaller than expected for the overburden from the sediment thickness of the Kazusa Group. An excess fluid pressure interval was also identified in the lower part of the basin fill, where several large-scale (several kilometres in length and several tens of metres thick) mass-transport deposits (MTDs) are intercalated. This interval is characterized by high porosity and small consolidation yield stresses, indicating that consolidation had been retarded by the excess fluid pressure. The estimated excess fluid pressure was c. 5–7 MPa. In addition, outcrop-scale fluidization and minor liquefaction features were identified within and below the high fluid pressure interval. The excess fluid pressure reduced the effective stress in the Boso forearc basin and, subsequently, the stability of the slope, allowing small tectonic events to generate submarine landslides. Therefore, the formation of these large-scale MTDs was probably related to the excess fluid-pressure generation.

scholarly journals Morphology and spatio-temporal distribution of lacustrine mass-transport deposits in Wörthersee, Eastern Alps, Austria

2019 ◽  
Vol 500 (1) ◽  
pp. 235-254 ◽  
Author(s):  
Christoph Daxer ◽  
Maddalena Sammartini ◽  
Ariana Molenaar ◽  
Thomas Piechl ◽  
Michael Strasser ◽  
...  
Keyword(s):  
Mass Transport ◽  
Temporal Distribution ◽  
Late Glacial ◽  
Eastern Alps ◽  
Excess Pore Pressure ◽  
European Alps ◽  
Fine Grained ◽  
Spatio Temporal ◽  
Morphological Differences ◽  
Mass Transport Deposits

AbstractIn lakes, landslides can be studied in high resolution due to their accessibility and limited size. Here, we investigate mass-transport deposits in glacigenic Wörthersee (Eastern European Alps) by integration of seismic, sediment core and multibeam bathymetric data. Two outstanding landslide events were revealed: the first occurred in the Late Glacial, leading to multiple deposits of up to 15 m thickness; they consist of sandy turbidites and mudclast conglomerates, which are overlain by a 2.5 m thick megaturbidite. The extensive, likely earthquake-triggered failure linked to this event was preconditioned by rapid sedimentation of fine-grained glaciolacustrine sediments and associated build-up of excess pore pressure. The second event was presumably triggered by a major earthquake (Mw≈7) in AD 1348 and comprises a mass-transport complex and several landslides, which led to a c. 30 cm thick turbidite. In total, 62 landslides are imaged in the multibeam map, 6 of which are most likely human-induced. Some of these show horseshoe-type compressional ridges and frontal breaching, whereas others exhibit an extensive zone of rafted blocks. We attribute these morphological differences to four main factors: (1) slope gradient and changes therein; (2) preconditioning of the impacted zone; (3) volume of remobilized sediment; and (4) type of impactor.

Megaclasts within mass-transport deposits: their origin, characteristics and effect on substrates and succeeding flows

2020 ◽  
Vol 500 (1) ◽  
pp. 515-530 ◽  
Author(s):  
Jefferson Nwoko ◽  
Ian Kane ◽  
Mads Huuse
Keyword(s):  
Mass Transport ◽  
Seismic Reflection ◽  
Radial Flow ◽  
Submarine Landslide ◽  
Submarine Landslides ◽  
3D Seismic ◽  
Seafloor Topography ◽  
Basal Surface ◽  
Mass Transport Deposits ◽  
Substrate Influence

AbstractMegaclasts transported within submarine landslides can erode the substrate, influence the flow that transports them and, if they form seafloor topography, can influence subsequent flows and their deposits. We document grooves up to 40 km long formed by megaclasts carried in submarine landslides that scoured tens of metres deep into the contemporaneous substrate of the deep-water Taranaki Basin, New Zealand. A 1925 km2 3D seismic reflection survey records six mass transport deposits (MTDs) interbedded with turbidites. Here, we focus on three MTDs, labelled A (oldest), B and C (youngest). MTD-A features megaclasts that internally have coherent parallel strata, and formed striations 4–15 km long and 2–3 km wide, with protruding megaclasts that are onlapped by younger sediments. The seafloor expression of these megaclasts partially obstructed the submarine landslide that created MTD-B. MTD-B contains megaclasts that incised through the rugose topography of the underlying MTD-A, and formed divergent grooves on the basal surface of MTD-B (8–40 km long and 200–250 m wide), which suggest radial flow expansion where flows exited topographic confinement. MTD-C features grooves 2–6 km long and 100–200 m wide that terminate at megaclasts and which internally are characterized of highly deformed reflectors surrounded by a chaotic matrix. This study directly links megaclasts to the grooves they form, and demonstrates that markedly different styles of scouring and resultant grooves can occur in closely related MTDs.

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