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The landslide problem

机译：滑坡问题

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Abstract The synonymous use of the general term “landslide”, with a built-in reference to a sliding motion, for all varieties of mass-transport deposits (MTD), which include slides, slumps, debrites, topples, creeps, debris avalanches etc. in subaerial, sublacustrine, submarine, and extraterrestrial environments has created a multitude of conceptual and nomenclatural problems. In addition, concepts of triggers and long-runout mechanisms of mass movements are loosely applied without rigor. These problems have enormous implications for studies in process sedimentology, sequence stratigraphy, palaeogeography, petroleum geology, and engineering geology. Therefore, the objective of this critical review is to identify key problems and to provide conceptual clarity and possible solutions. Specific issues are the following: (1) According to “limit equilibrium analyses” in soil mechanics, sediment failure with a sliding motion is initiated over a shear surface when the factor of safety for slope stability (F) is less than 1. However, the term landslide is not meaningful for debris flows with a flowing motion. (2) Sliding motion can be measured in oriented core and outcrop, but such measurement is not practical on seismic profiles or radar images. (3) Although 79 {MTD} types exist in the geological and engineering literature, only slides, slumps, and debrites are viable depositional facies for interpreting ancient stratigraphic records. (4) The use of the term landslide for highvelocity debris avalanches is inappropriate because velocities of mass-transport processes cannot be determined in the rock record. (5) Of the 21 potential triggering mechanisms of sediment failures, frequent short-term events that last for only a few minutes to several hours or days (e.g., earthquakes, meteorite impacts, tsunamis, tropical cyclones, etc.) are more relevant in controlling deposition of deep-water sands than sporadic long-term events that last for thousands to millions of years (e.g., sea-level lowstands). (6) The comparison of H/L (fall height/runout distance) ratios of {MTD} in subaerial environments with H/L ratios of {MTD} in submarine and extraterrestrial environments is incongruous because of differences in data sources (e.g., outcrop vs. seismic or radar images). (7) Slides represent the pre-transport disposition of strata and their reservoir quality (i.e., porosity and permeability) of the provenance region, whereas debrites reflect post-transport depositional texture and reservoir quality. However, both sandy slides and sandy debrites could generate blocky wireline (gamma-ray) log motifs. Therefore, reservoir characterization of deep-water strata must be based on direct examination of the rocks and related process-specific facies interpretations, not on wireline logs or on seismic profiles and related process-vague facies interpretations. A solution to these problems is to apply the term “landslide” solely to cases in which a sliding motion can be empirically determined. Otherwise, a general term {MTD} is appropriate. This decree is not just a quibble over semantics; it is a matter of portraying the physics of mass movements accurately. A precise interpretation of a depositional facies (e.g., sandy slide vs. sandy debrite) is vital not only for maintaining conceptual clarity but also for characterizing petroleum reservoirs.
机译：摘要滑坡，滑坡是内置的通用术语的同义词，它适用于所有种类的运输沉积物（MTD），包括滑坡，塌陷，碎屑，倾倒，蠕变，碎屑崩塌等。在航空，湖底，海底和地外环境中，已经产生了许多概念上和命名上的问题。此外，触发器的概念和群众运动的长跳动机制没有严格要求。这些问题对过程沉积学，层序地层学，古地理学，石油地质学和工程地质学的研究具有重大意义。因此，本次严格审查的目的是确定关键问题并提供概念上的明确性和可能的​​解决方案。具体问题如下：（1）根据土壤力学中的“极限平衡分析”，当边坡稳定性的安全系数（F）小于1时，会在剪切面上引发具有滑动运动的沉积物破坏。但是， “滑坡”一词对运动中的泥石流没有意义。 （2）可以在定向的岩心和露头中测量滑动运动，但是这种测量在地震剖面或雷达图像上不可行。 （3）尽管地质和工程文献中存在79种{MTD}类型，但只有滑坡，塌陷和碎屑才是解释古代地层记录的可行沉积相。 （4）将滑坡一词用于高速碎屑崩塌是不合适的，因为无法在岩石记录中确定质量传输过程的速度。 （5）在21种潜在的沉积物破坏触发机制中，仅持续几分钟到几小时或几天的频繁短期事件（例如地震，陨石撞击，海啸，热带气旋等）在以下方面更为相关：与持续数千到数百万年的零星长期事件（例如，海平面低位）相比，控制深水沙的沉积更为重要。 （6）由于数据源的差异（例如露头），在海底环境中{MTD}的H / L（下降高度/跳动距离）比率与在海底和陆地外环境中{MTD}的H / L比的比较是不一致的。对比地震或雷达图像）。 （7）滑坡代表物源区的运输前地层分布及其储层质量（即孔隙度和渗透率），而碎屑则反映了运输后的沉积质地和储层质量。然而，沙质滑坡和沙质碎屑都可能产生块状的有线（伽马射线）原木图案。因此，深水地层的储层表征必须基于对岩石的直接检查和相关的过程特定相解释，而不是基于电缆测井或地震剖面和相关的过程模糊相解释。这些问题的解决方案是仅将“滑坡”一词应用于可以凭经验确定滑动的情况。否则，一般的术语{MTD}是合适的。该法令不仅仅是对语义的质疑;这是准确描绘大众运动的物理学问题。准确解释沉积相（例如，砂质滑移与砂质碎屑）不仅对保持概念清晰性而且对表征石油储层都至关重要。

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