Application of the Newmark Analysis Method in Stability Evaluation of Submarine Slope

The Newmark seismic time-history analysis method can take into account the effects of natural seismic peak ground acceleration (PGA), duration, and seismic frequency; seismic wave can be input into the method for simulation. This study calculates the dynamic response of the typical seabed slope of Caofeidian in the event of a similar Tangshan earthquake, and the displacement value can be used to quantitatively reflect the influence of the earthquake on the slope of the site. The allowable displacement value of the top of buildings or submarine slope can be used as a marker of security and stability analysis, which can further provide important reference for similar slope stability evaluation and offshore engineering construction.

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

<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>

Research on deformation of submarine slope in Zhoushan Islands by in-situ observation

Instability of submarine slopes in Zhoushan Islands is widespread. Frequent submarine landslides pose a great threat to offshore facilities such as submarine optical cables, reclamation projects, ports and docks. In this paper, a self-developed in-situ observation system is used to observe the deformation of submarine slopes on the southwest side of Zhujiajian Island in Zhoushan Islands for 75 days. The results show that the deformation characteristics of sediments at different depths of the submarine slope are different, and the lateral deformation of bottom sediments is about 0.75 mm, which is three times as much as the deformation of overlying sediments. The deformation process presents a step-like change, and the deformation direction is consistent with the trend of submarine slope.

Underestimated angle of submarine slope at failure: A short discussion

Submarine landslides always occur along gently inclined continental slopes, but the reasons for such failure of low-angle submarine slopes are unclear and contentious. A short discussion is presented here to some recent published papers including some inspirations about the low-angle failure of submarine slopes. Because fluid overpressure could lead to steepening slopes before landslide, the inclination of the slopes at failure may be underestimated. We offer a new perspective on low-angle failure of low-permeability slopes.

Faunistické společenstvo kroměřížského souvrství na lokalitě Litenčice (karpatská předhlubeň, střední Morava)

The fossil assemblages of the foraminifers, bryozoans, molluscs, corals, decapods, sharks and teleosteans were analysed from the Litenčice sand pit in the middle part of the Carpathian Foredeep. The section can be assigned to the Karpatian Stage of the Central Paratethys regional stratigraphy (uppermost Lower Miocene) on the basis of species Uvigerina graciliformis Papp et Turn., Lampanyctus carpaticus (Brz.) and Agapilia pachii (Hoern.). Rich and diversified assemblages indicate mainly shallow water marine environment. Foraminifers and molluscs indicate salinity perturbations. Bryozoans and also molluscs document environment with relatively high dynamics and depth of water about 100 m. Foraminifers, fishes and sharks represent deeper water taxa and indicate a possible reworking of shallow-water elements. The studied sands and gravels of the Holešov Member of the Kroměříž Formation are interpreted as sediments of gravitational currents, more precisely dense turbidity currents (high-density turbidity currents) in the sense of Lowe (1982). The deposition environment can probably be placed on the submarine slope of the coarse-grained delta of the Gilbert type (so-called foresets). This study provided evidence of a number of fossil groups that occur at the site.