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Methane from Gas Hydrates
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
Since hydrates prevent sediment compaction, their in situ dissociation can also cause climate change and falling of sea level. If the hydrate breaks down, it will weaken the sediment and may cause submarine landslides and simultaneously release methane into the atmosphere. The methane released from the reservoir to the atmosphere can contribute to the climate change. Submarine landslides can cause tsunamis and catastrophic coastal flooding. The thickness of the gas hydrate stability zone (GHSZ) in continental margins depends on water depth (hydrostatic pressure), water temperature, geothermal gradient, and gas composition [1,60] (Tohidi, 2013, pers. comm.).
Interaction between submarine landslides and suspended pipelines with a streamlined contour
Published in Marine Georesources & Geotechnology, 2018
Ning Fan, Ting-kai Nian, Hou-bin Jiao, Yong-gang Jia
Submarine landslides are a common and frequent marine geohazard. They can lead to a large volume of sediment movement, and these sediments may travel hundreds of kilometers in less than 1 h to over several days, even on gentle slopes (<1°) (Holcomb and Searle 1991; Locat and Lee 2002; Hance 2003; Sahdi et al. 2014; Jia et al. 2016). In previous studies, the fastest landslide movement, located in the North Sea fan off the west coast of Norway, was reported to be nearly 30 m/s in velocity (De Blasio et al. 2004; Zakeri, Høeg, and Nadim 2008). On these occasions, submarine landslides have the potential to seriously damage fixed platforms, submarine pipelines, cables, and other seafloor installations (Miao 2007; Chatterjee,White, and Randolph 2012; Zakeri, Hawlader, and Chi 2012; Jeong et al. 2013; Zhang et al. 2016), especially submarine pipelines, which undertake the essential transportation function in ocean resource development and whose slender structure is easily destroyed (Kim, Lee, and Yeon 2011). Therefore, studies of the interaction between submarine landslides and pipelines and the techniques for reducing landslide impact are extremely important.
Simulation of runout behavior of submarine debris flows over regional natural terrain considering material softening
Published in Marine Georesources & Geotechnology, 2023
Yangming Chen, Lulu Zhang, Xin Wei, Mingjing Jiang, Chencong Liao, Hailei Kou
Submarine landslides are one of the most hazardous geological threats to subsea infrastructure since they can transport a considerable volume of sediment across continental slopes. After initiation, submarine landslides quickly transform into submarine debris flows due to water intake (De Lange et al. 2020; Jeong et al. 2013; Yin and Rui 2018). Affected by gravity and water, the strength of sliding material decreases gradually (De Blasio et al. 2005; Harbitz et al. 2003), resulting in extremely long-runout distance and particularly high velocity of submarine debris flows (De Blasio et al. 2005; Harbitz et al. 2003; Kim et al. 2019): the runout distance of a submarine debris flow may reach hundreds of km on very gentle continental slopes (0.5–3.0°) (De Blasio et al. 2005; Issler et al. 2005; Rui and Yin 2019) and the maximum velocity of a submarine debris flow may reach 20 m/s (De Blasio et al. 2004b; Leynaud, Sultan, and Mienert 2007; Wang et al. 2016). With such a huge impact area and high velocities, submarine debris flows are extremely dangerous for regional offshore infrastructures, such as subsea pipelines and communication cables (X. Y. Chen, Zhang, Zhang, et al. 2020; Fan et al. 2018; Li, Chen, and Liao 2021; Wang, Fu, and Qin 2020; Zakeri, Høeg, and Nadim 2008; Zakeri 2009; Zakeri, Høeg, and Nadim 2009). For engineering practice, rapid and accurate evaluation of runout behavior of submarine debris flows in regional natural terrain considering material softening is of great significance because of its fundamental role in quantitative evaluation of the areas vulnerable to disaster and the intensity of a potential disaster.
Large-scale seafloor stability evaluation of the northern continental slope of South China Sea
Published in Marine Georesources & Geotechnology, 2020
Xing-sen Guo, De-feng Zheng, Ting-kai Nian, Le-ting Lv
Based on GIS techniques, the terrain slope gradients of the northern continental slope of the South China Sea were obtained, and a historical earthquake distribution map was produced. Combined with the acquired physical and mechanical data of the marine soils, a large-scale seafloor seismic stability evaluation of the northern continental slope was carried out. The main conclusions were as follows. The northern continental slope can be divided into five segments, and while the overall slope gradient is low, many areas exhibit high slope gradients. The distribution of seismic activity is quite uneven, showing that the seismic activity in the east and north is strong and that the seismic activity in the west and south is weak. Seismic action is one of the most significant causes of submarine landslides.The formulas for calculating the safety factor based on the limit equilibrium method of an infinite slope model are derived, and they provide a theoretical basis for quantitative evaluation. The physical and mechanical parameters of the marine soil, slope gradient and horizontal seismic action are important factors affecting the stability of submarine slopes.Regional stability evaluation of the northern continental slope of the South China Sea under different seismic conditions is achieved, and intuitive and quantitative distributions of the risk zones are given. Under strong seismic action, the Shenhu, Zhujiang Valley and Taiwan Bank slope segments will exhibit large-scale instability, which must be taken seriously.