Structure and evolution of mass transport deposits in the South Caspian Basin, Azerbaijan

Richardson, Steve E. J.; Davies, Richard J.; Allen, Mark B.; Grant, Simon F.

doi:10.1111/j.1365-2117.2011.00508.x

Cited by 42 publications

(32 citation statements)

References 67 publications

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“…Boundary conditions at the ends of the shear band prescribe zero displacements 16) where the first condition is satisfied by equation (3.16) automatically, while the second one can be approximated as 17) leading to the following relationship (figure 6):…”

Section: Z = F(x)mentioning

confidence: 99%

“…According to the geological data, this landslide generated a tsunami wave with a height of 10-12 m on the coast of Norway; on the Shetland Islands, it was higher than 20 m [13]. Many other examples exist in the geological record and are often observed on industry-acquired geophysical data [14][15][16]. The common features of the above landslides are that they are very long (10 1 -10 2 km), relatively shallow (less than 10 2 m thick) and occur in very mild continental slopes (inclination less than 10 −1 ) built of normally consolidated sediments.…”

Section: Introduction (A) Submarine Landslidesmentioning

confidence: 99%

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Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides

Puzrin

Gray²,

Hill

2015

Proc. R. Soc. A.

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A simple approach to slope stability analysis of naturally occurring, mild nonlinear slopes is proposed through extension of shear band propagation (SBP) theory. An initial weak zone appears in the steepest part of the slope where the combined action of gravity and seismic loads overcomes the degraded peak shear resistance of the soil. If the length of this steepest part is larger than the critical length, the shear band will propagate into the quasi-stable parts of the slope, where the gravitational and seismically induced shear stresses are smaller than the peak but larger than the residual shear strength of the soil. Growth of a shear band is strongly dependent on the shape of the slope, seismic parameters and the strength of soil and less dependent on the slope inclination and the sensitivity of clay. For the slope surface with faster changing inclination, the criterion is more sensitive to the changes of the parameters. Accounting for the actual nonlinear slope geometry eliminates the main challenge of the SBP approach-determination of the length of the initial weak zone, because the slope geometry can be readily obtained from submarine site investigations. It also helps to identify conditions for the early arrest of the shear band, before failure in the sliding layer or a change in loading or excess pore water pressures occurs. The difference in the size of a landslide predicted by limiting equilibrium and SBP approaches can reach orders of magnitude, potentially providing an explanation for the immense dimensions of many observed submarine landslides that may be caused by local factors acting over a limited portion of the slope.

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Section: Z = F(x)mentioning

confidence: 99%

Section: Introduction (A) Submarine Landslidesmentioning

confidence: 99%

Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides

Puzrin

Gray²,

Hill

2015

Proc. R. Soc. A.

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“…These correspond to the initial definition of mass-transport deposits (MTDs) proposed by Weimer (1989). Reviews of MTDs imaged by better quality seismics than in that initial work can be found in Moscardelli et al (2006) and Bull et al (2009); a detailed study of MTDs around the Shah Deniz anticline is provided by Richardson et al (2011). In the present article, the four MTDs are numbered MTD 1 to MTD 4 from the top of the section downward.…”

Section: Regional Stratigraphymentioning

confidence: 68%

“…In this prolific onshore and offshore oil and gas province, sediment remobilization has been the subject of numerous publications this last decade, in particular related to mud volcanoes (e.g., Fowler et al 2000;Planke et al 2003;Yusifov and Rabinowitz 2004;Evans et al 2006) and mud volcano systems . More recently, Richardson et al (2011) focused on mass-transport complexes. The present study investigates a massive (several kilometers in diameter), buried crater-like structure associated with a mass-transport deposit at the crest of the Absheron anticline.…”

Section: Introductionmentioning

confidence: 99%

How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!

2014

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The crest of the Absheron anticline in the South Caspian Basin at a few hundred meters below the present seafloor shows a subcircular depression about 8 km in diameter and 200 m deep, bounded by steep edges dipping 15°to 45°into it. The depression and the surrounding series are respectively filled and overlain by a regional mass-transport deposit (MTD) 150 m thick outside the depression and 300 m thick inside, composed mostly of extensional blocks. Geometric and stratigraphic analyses indicate that 150 m of initially deposited sediment were removed from a closed area after burial. Seismic evidence of shallow gas accumulations below the crater-like feature suggests that gas likely played a significant role in its development. The model proposed for the emplacement of the crater is that the gas-bearing cover of a shallow gas reservoir underwent exsolution when its overburden thinned during an episode of extensional slope failure. This resulted in loss of resistance to shear and evacuation of the gas-bearing sediment, likely at the shearing base of the failed mass. This evacuation feature is considered an example where the presence of gas locally governs the morphology of an MTD. The interpreted process shows a positive feedback between slope failure and loss of strength at the base of the resulting MTD.

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“…Gee et al, 2006;Loncke et al, 2009;Richardson et al, 2011). Typically, limiting equilibrium (LE) analysis underlies the probabilistic modelling, which assumes that failure takes place simultaneously along the entire sliding surface where the shear stress exceeds the peak shear strength.…”

Section: Introductionmentioning

confidence: 99%

Application of the Shear Band Propagation Method to Slope Stability Analysis of a Palaeo-Landslide in the Caspian Sea

Gray¹,

Puzrin

Hill

2015

All Days

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Geophysical observations of palaeolandslides in offshore settings include long and relatively thin failures that occur on very mild slopes. Back analysis of such failures using the limiting equilibrium approach and measured geotechnical soil properties is typically used to inform the likely causes of past failures. An assessment can then be made of the present day significance of causal factors (e.g. the presence of excess pore water pressure), with the limiting equilibrium approach used to assess factors of safety for present-day slopes and predict the potential size of any future failures. However, for long, thin slides, use of the limiting equilibrium approach can lead to the conclusion that either a significantly large seismic trigger or other, abnormal geological condition was required to initiate failure. A result has been the focusing of academic research into other failure causes and conditioning factors. Further, the stability of the present day seabed for offshore developments can be overestimated, given the rarity of large seismic events in many areas and geotechnical measurements that not always show abnormal soil conditions. The shear band propagation approach offers an alternative view, where an initial small failure can grow into a larger failure at the point of initiation. A result is that an explanation of the conditions leading to failure can be attributed to many submarine landslides. Further, accounting for the potential propagation of a shear band in the future prediction of submarine landslides can result in greater predicted failure sizes and lower factors of safety than using limiting equilibrium only. The application of the shear band propagation approach to back analyse a palaeolandslide in the ACG Field, Caspian Sea, is used to demonstrate the methodology and compare with results using the limiting equilibrium approach. Results show that the shear band propagation approach successfully predicts observed failure geometries and suggests triggering conditions from a lower magnitude seismic event compared to that predicted using limiting equilibrium. The future application of shear band propagation theory to submarine landslide analysis is also discussed.

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Structure and evolution of mass transport deposits in the South Caspian Basin, Azerbaijan

Cited by 42 publications

References 67 publications

Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides

Significance of the actual nonlinear slope geometry for catastrophic failure in submarine landslides

How to evacuate 10 km3 of mud: saturate with gas and decrease the pressure!

Application of the Shear Band Propagation Method to Slope Stability Analysis of a Palaeo-Landslide in the Caspian Sea

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