The landslide problem
The landslide problem
复制标题
DOI：
10.3724/sp.j.1261.2015.00071
复制
发表时间：
2015-04
期刊：
影响因子：
--
通讯作者：
G. Shanmugam;Y. Wang
中科院分区：
文献类型：
--
作者：
G. Shanmugam;Y. Wang
摘要：通用术语“滑坡”的同义使用（内在指的是滑动运动）适用于所有种类的质量输送沉积物（MTD），包括地下、湖底、海底和地外环境中的滑坡、滑坡、碎屑、倾倒、蠕变、碎屑雪崩等，这造成了许多概念和命名问题。此外，群众运动的触发器和长期运行机制的概念应用得松散，缺乏严谨性。这些问题对于过程沉积学、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巨大的意义。因此，这次批判性审查的目的是确定关键问题并提供概念清晰度和可能的解决方案。具体问题如下：（1）根据土力学中的“极限平衡分析”，当边坡稳定安全系数（F）小于1时，在剪切面上就会引发滑动运动的沉积物破坏。然而，滑坡一词对于流动运动的泥石流没有意义。 (2) 可以在定向岩心和露头中测量滑动运动，但这种测量在地震剖面或雷达图像上不实用。 (3) 尽管地质和工程文献中存在 79 种 MTD 类型，但只有滑坡、滑塌和碎屑岩是解释古代地层记录的可行沉积相。 (4) 使用滑坡一词来描述高速碎片雪崩是不合适的，因为在岩石记录中无法确定质量传输过程的速度。 (5) 在21种潜在的沉积破坏触发机制中，仅持续几分钟至数小时或数天的频繁短期事件（例如地震、陨石撞击、海啸、热带气旋等）比持续数千年至数百万年的零星长期事件（例如海平面低位）对控制深水沙粒沉积的影响更大。 (6) 由于数据源（例如露头与地震或雷达图像）的差异，地面环境中 MTD 的 H/L（坠落高度/跳动距离）比与海底和地外环境中 MTD 的 H/L 比的比较不一致。 (7) 滑坡代表了物源区地层搬运前的配置及其储层质量（即孔隙度和渗透率），而岩屑则反映了搬运后的沉积结构和储层质量。然而，沙质滑坡和沙质碎屑都可能产生块状绳索（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过程特定相解释，而不是基于电缆测井或地震剖面和相关过程模糊相解释。这些问题的解决方案是仅将术语“滑坡”应用于可以凭经验确定滑动运动的情况。否则，通用术语 MTD 是合适的。这项法令不仅仅是语义上的争论；这是准确描述质量运动的物理原理的问题。沉积相（例如，砂质滑坡与砂质碎屑）的精确解释不仅对于保持概念清晰度至关重要，而且对于表征石油储层也至关重要。
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.