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一种基于水深梯度原理的海底滑坡快速识别方法——以南海北部陆坡白云深水区为例 总被引：3，自引：2，他引：1
如何快速而准确的识别并提取海底滑坡的特征形态信息一直是海洋工程地质、特别是深水工程地质评价中所关注的问题之一。本文根据滑坡后形成的地形形态,基于水深梯度求值运算的原理,通过Matlab编程建立了一种快速识别海底滑坡的方法。以南海北部陆坡白云深水区为例进行海底滑坡的识别,并利用浅地层剖面做验证,结果显示这一方法是可行的,其最大的优点是滑坡识别速度快,对于规模小且数量多的滑坡识别效率较高。通过实测数据进一步的分析表明:（1）阈值的选取对识别结果有明显影响,阈值的选取需要结合其他物探资料（如浅地层剖面和声呐影像）综合判断来确定;（2）水深数据的空间分辨率会影响滑坡识别结果的准确度,合适的空间分辨率会提高识别结果的准确性。 相似文献
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洋中脊是板块扩张和洋壳增生的主要区域,除了发育沿洋脊走向的裂隙式喷发火山脊,还分布有众多零星的中心式喷发火山锥。这些火山锥的形态和分布对了解洋中脊构造和岩浆活动具有重要的指示意义。基于海底多波束地形数据,采用人工或机器解译方法可以识别这些火山锥。本文利用大洋24航次船载多波束测深获得的卡尔斯伯格脊DEM(数字高程模型)数据,以非监督分类为手段,开展洋中脊火山锥的自动提取方法研究。基于原始DEM计算地形坡度、地表粗糙度、正负地形等衍生参数,进行特征变换,提取火山锥的特征信息。使用ISO(迭代自组织)聚类方法对特征变换后的图像进行聚类分析,并利用景观形状指数进行几何筛选,完成火山锥的自动提取。所使用的海底火山锥自动识别方法,正确率达0.8,重叠率约0.7,识别效果较好,效率高,能够在海底大范围的火山锥解译中发挥重要作用。 相似文献
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利用广州海洋地质调查局在南海北部神狐钻探区采集的高分辨率地震数据,结合2007年第一次水合物钻探航次(GMGS01)获取的岩心资料,从宏观地震反射结构、微观岩心粒度特征两个方面对GMGS01区块内残留在峡谷群脊部的细粒浊积体进行特征识别和刻画。研究结果显示,似海底反射(bottom simulating reflectors,BSR)之上存在着2套特征不同的沉积单元,位于下部的沉积单元1表现为薄层杂乱透镜状的地震反射特征,对应于粒度C-M图版中与C=M基线近似平行的含水合物层段的样品,被解释为峡谷群脊部的细粒浊积体。选取穿过神狐海域峡谷群中第16条海底峡谷的8条测线为研究对象,能够揭示沉积单元1(细粒浊积体)自北向南的空间变化特征,从而进行分布范围的确定。神狐海域沉积过程分析表明,峡谷群脊部的细粒浊积体是北部小型水道侵蚀下伏沉积物并发生再搬运和再沉积的结果。利用区域性覆盖的二维地震资料,本次研究确定了小型水道的北部侵蚀边界。综合GMGS01区块细粒浊积体的地震反射特征、穿过神狐海域东部第16号海底峡谷自北向南的地震反射差异、研究区北部小型水道的侵蚀边界,本次研究利用两点确定一线和相似平行的方法,在整个神狐海域初步确定了峡谷群脊部细粒浊积体的分布范围。细粒浊积体沉积边界的识别,将为从深水沉积的角度探讨神狐海域水合物不均匀性分布提供依据,同时也能进一步揭示该区域峡谷群脊部水合物的成藏机制和富集规律。 相似文献
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海底沙波特征线的最优方向剖面自动识别方法 总被引：2，自引：2，他引：0
海底沙波是发育在近海陆架上的一种常见海底地貌类型,海底沙波特征与运动规律的研究具有重要的科学意义与工程应用价值,沙波脊线与谷线是表征海底沙波的最基本特征,也是精确描述沙波运动的基本参量。本文提出了一种基于复合数字水深模型的沙波特征线自动识别方法——最优方向剖面法,基于水深曲面归算得到最优剖面方向,再依据最优剖面方向求导并判定极值,自动提取沙波形态特征点,最终形成沙波脊线和谷线。以台湾浅滩复合型沙波为例进行对比实验研究,结果表明,该方法能基于不同分辨率的数字水深模型自动准确地提取海底沙波脊线与谷线,勿需设置阈值,地形自动化识别程度得到进一步提升,具有重要的实际应用价值。 相似文献
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基于最新的高分辨率多波束全覆盖测深数据、单道地震和多道地震剖面数据,对南海北部陆坡一统峡谷群9条峡谷的地形地貌及沉积特征进行了分析:峡谷群自陆坡向深海盆方向呈聚敛型,横断面主要呈"V"型,谷壁对称发育,坡度较陡;研究区海底地层受多条断裂控制,呈典型阶梯状发育,海底断陷、重力滑塌面和小型滑坡体等海底不稳定地质灾害高度发育,说明峡谷群海底环境处于极不稳定状态。在研究区海底峡谷群地貌演化过程中,西沙海槽区域沉降等新生代构造运动控制着峡谷群地貌格局的形成;来自北部陆架的充足沉积碎屑物质的输入往往伴随着高密度浊流、海底滑坡、坍塌等海底灾害的发生,控制着峡谷群的进一步发育;相对海平面变化直接改变了研究区的沉积环境,为陆源碎屑物质的搬运提供了更加直接的通道,这也是诱发陆坡海底失稳、塑造峡谷群地貌特征的重要因素之一。 相似文献
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《海洋地质与第四纪地质》2017,(5)
利用广州海洋地质调查局采集的2D和准3D地震资料,从整体形态、期次性和内部结构等方面对南海北部陆坡神狐海域内广泛发育的沉积物失稳进行了类型划分和特征描述,并将沉积物失稳的分布特征和陆坡限制型海底峡谷群的分段性进行耦合关联,进而分析沉积物失稳的空间变化规律。研究结果显示,沉积物失稳可以划分为两种类型:第一种类型位于峡谷群的下游段,几乎不受峡谷群地貌的影响,表现为多期次、内部连续和自北向南的块体运动方式,主要以"残留"的形式位于峡谷群脊部;另一种类型主要表现为沿峡谷群脊部向谷底的块体运动方式,受到峡谷群地形起伏的影响,在峡谷群头部,主要为多期次滑移体,中游段变形强度最大,滑塌体是主要的类型,而在下游段-嘴部,表现为滑移块体。第四纪以来,源自北部珠江水系充足的沉积物供给和自北向南较陡的海底地形,是沉积物失稳发育的关键控制因素;陆坡限制型海底峡谷群可能造成了沉积物的再次变形作用,使得沉积物失稳的空间变化规律与峡谷群分段性具有对应关系。此外,神狐海域含气流体的垂向运移以及水合物矿体的存在,也是研究区内沉积物失稳的重要控制因素。 相似文献
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珠江口盆地陆架坡折带海底滑坡及其影响因素 总被引：3，自引：1，他引：2
为了解海底滑坡在陆架坡折演化过程中所起的作用并分析影响海底滑坡发育的因素,以最新采集的二维和三维地震资料为基础,综合运用了地貌分析和地震解释技术,通过对滑坡的地貌形态特征及地震响应特征进行详细刻画,在珠江口盆地陆架坡折带新近纪地层中识别出多处海底滑坡,明确了其分布范围并建立了滑坡发育的地质模式。分析认为,珠江口盆地相对海平面变化和流体活动的综合作用是导致研究区海底不稳定的主要因素。海底滑坡发源于海底峡谷的朔源侵蚀,向上陆坡扩展并终止于陆架坡折带。 相似文献
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东海陆坡不同类型海底峡谷的分布构造响应 总被引：1，自引：0，他引：1
利用1997-2001年在东海海域获得的多波束全覆盖测深数据和收集的部分高分辨率单道地震剖面,对东海陆坡海底峡谷的地形要素,如长度、弯曲度、平均坡度、剖面特征、头部和末端的水深等进行了详细的分析和统计.根据平面形态将海底峡谷划分为3种类型:直线型、蛇曲型和树枝型.海底峡谷主要分布于中段和南段的东海陆坡之上,平面形态特征总体上自北向南趋于复杂(直线型→蛇曲型→树枝型),规模逐渐增大,不同平面类型代表了峡谷不同的演化阶段.峡谷的分布格局和变化趋势主要受控于冲绳海槽扩张背景下的构造活动. 相似文献
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海底峡谷作为海洋中油气勘探的重要指示器和富集场所,研究其复杂的水动力系统变得十分重要。海底峡谷中水动力系统包括了重力流、浊流、潮汐/内潮汐、内波、底层流、上升流和高密度陆架瀑布流(Dense Shelf Water Cascading)等要素,与峡谷外有明显的不同。首次从海底峡谷水动力系统的综合概况出发,研究了水动力作用对峡谷的侵蚀、沉积物的搬运与沉积以及特殊生态系统的塑造,总结分析了峡谷中水动力系统的主要研究手段。结果表明,海底峡谷中的水动力作用由于成因不同,各自的表现特征也不一样;重力流、内潮汐、上升流等水动力作用对峡谷的形态地貌、物质搬运以及生态系统的影响较为显著;对于常用的4种水动力系统的研究方法而言,其研究背景各不相同,且存在一定的局限性。本文为我国海底峡谷水动力系统的研究起到了一定的指导作用。 相似文献
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海底峡谷在全球陆缘广泛分布，是浅海沉积物向深海运移的主要通道，对于理解深海浊流触发机制、深海沉积物的搬运模式、深海扇的发育历史和深海油气资源勘探等均具有重要意义。本文基于高分辨率高精度的多波束测深数据，首次对南海东北部海底峡谷体系进行了研究，精细刻画了高屏海底峡谷、澎湖海底峡谷、台湾浅滩南海底峡谷和东沙海底峡谷等4条大型海底峡谷的地貌特征并分析其发育控制因素。海底坡度、构造运动、海山与海丘是影响南海东北部峡谷群走向与特征的重要因素，其中，海底坡度对于峡谷上游多分支与“V”字特征有显著的控制作用；构造运动是控制高屏海底峡谷走向的因素，澎湖海底峡谷的走向则与菲律宾海板块与欧亚板块碰撞有关，东沙海底峡谷的走向则与东沙运动相关，台湾浅滩南海底峡谷上段受NW向断裂构造的控制；海山的阻挡作用造成峡谷局部走向和特征改变。海底峡谷群输送大量陆源沉积物到深海盆并形成大面积的沉积物波，海山和沉积物波的发育导致东沙海底峡谷下段“回春”和转向。 相似文献
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南海北部陆坡发育众多海底峡谷,其形成、发育、演化过程都存在较大差异。本文选取南海北部陆坡典型的珠江口外海底峡谷群、东沙海底峡谷、台湾浅滩南海底峡谷和澎湖海底峡谷进行研究,通过高分辨率多道地震数据和多波束测深数据,结合前人研究成果,对4条典型海底峡谷的形态特征、沉积充填特征及结构、形成发育过程及控制因素进行研究。结果表明,南海北部陆缘各个海底峡谷的形成受多个控制因素的影响,其影响程度及方式都有差别。构造活动、海平面变化及沉积物重力流与海底峡谷的演化密切相关,而陆地河流和局部构造因素也以不同方式影响着海底峡谷的发育。对于发育在主动大陆边缘的台湾岛东南侧的澎湖海底峡谷,其板块运动和岩浆活动活跃,其上发育的海底峡谷的控制因素以内营力地质作用为主。而具有被动大陆边缘属性的其他3条峡谷,由于构造运动较少或停止,其上发育的海底峡谷的控制因素以外营力地质作用为主。 相似文献
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Sediments of the continental slope are commonly bioturbated by endo- and epibenthic organisms, particularly in and around submarine canyons and channels. This study reviews the architecture and depositional environments associated with canyons and channels on the continental slope, and assesses the key physical and chemical conditions encountered in and around these conduits. Hydrodynamic energy, concentration and quality of organic carbon, dissolved oxygen concentration and sedimentation rate are identified as key controls on the composition of benthic ecosystems in slope environments. Submarine canyons and channels focus a variety of turbid and clear-water currents, all of which serve to increase the concentration of oxygen, labile organic carbon and other nutrients, which tend to elevate the abundance and biodiversity in the seafloor sediments, compared with those of the surrounding slope. Ancient slope channel and canyon systems reflect some of the variation in ichnological assemblages that is seen in modern analogues, although processes of erosion and trace fossil preservation mean that the benthic environment is often incompletely preserved in the ancient record. By integrating current understanding of sedimentology, oceanography, biology and ichnology of slope environments it is possible to provide a first order summary of the inter-relationships between ichnology and depositional environments on the continental slope. The combination of these data has the potential to improve our understanding of changes in deep marine benthic ecosystems through geological time, and to further the use of ichnology in assessing hydrocarbon reservoir presence, quality and performance from bioturbated slope, canyon and channel-levee hydrocarbon reservoirs. 相似文献
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基于水下自主航行器(AUV)的神狐峡谷谷底块体搬运沉积特征及其对深水峡谷物质输运过程的指示 总被引：2，自引：0，他引：2
海底峡谷是陆源物质向深海运移的重要通道。对于远离陆地的海底峡谷,通常认为浊流是物质搬运的主要营力。受限于探测精度和复杂作业环境影响,使用常规地球物理资料对深水海底峡谷尤其是对谷底沉积体的形态和结构特征的刻画不够精细。基于水下自主航行器(AUV,Autonomous Underwater Vehicle)采集的高分辨率多波束、旁扫声呐和浅地层剖面资料,对神狐峡谷群中的一条峡谷的谷底表面及部分浅部地层的沉积特征进行了分析。结果表明,峡谷谷底浅部地层并不像它平滑的表面那么简单,而是由大量内部杂乱弱反射、厚度在8.4 m及以下的块体搬运沉积体组成。峡谷中下游块体搬运沉积体大都沿峡谷走向整体呈条带状展布,不是直接来源于相邻的峡谷脊部。研究认为在特定沉积环境下(例如高海平面时期),陆坡限定性峡谷谷底的块体搬运沉积过程的重复进行是峡谷谷底物质输运的重要途径,与浊流共同雕刻了峡谷的地形地貌。基于AUV的地球物理探测技术将是研究海底浅表层沉积过程和保障海底工程施工的重要手段。 相似文献
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南海北部白云深水区东北部小型峡谷内的块体搬运 总被引：2，自引：1，他引：1
The process of mass movements and their consequent turbidity currents in large submarine canyons has been widely reported, however, little attention was paid to that in small canyons. In this paper, we document mass movements in small submarine canyons in the northeast of Baiyun deepwater area, north of the South China Sea(SCS), and their strong effects on the evolution of the canyons based on geophysical data. Submarine canyons in the study area arrange closely below the shelf break zone which was at the depth of –500 m. Within submarine canyons, seabed surface was covered with amounts of failure scars resulted from past small-sized landslides. A complex process of mass transportation in the canyons is indicated by three directions of mass movements.Recent mass movement deposits in the canyons exhibit translucent reflections or parallel reflections which represent the brittle deformation and the plastic deformation, respectively. The area of most landslides in the canyons is less than 3 km2. The trigger mechanisms for mass movements in the study area are gravitational overloading, slope angle and weak properties of soil. Geophysical data indicate that the genesis of submarine canyons is the erosion of mass movements and consequent turbidity currents. The significant effects of mass movements on canyon are incision and sediment transportation at the erosion phases and fillings supply at the fill phases. This research will be helpful for the geological risk assessments and understanding the sediment transportation in the northern margin of the SCS. 相似文献
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High-resolution and high-density 2-D multichannel seismic data, combined with high-precision multibeam bathymetric map, are utilized to investigate the characteristics and distribution of submarine landslides in the middle of the northern continental slope, South China Sea. In the region, a series of 19 downslope-extending submarine canyons are developed. The canyons are kilometers apart, and separated by inter-canyon sedimentary ridges. Numerous submarine landslides, bounded by headscarps and basal glide surfaces, are identified on the seismic profiles by their distorted to chaotic reflections. Listric faults and rotational blocks in head areas and compressional folds and inverse faults at the toes of the landslides are possibly developed. Three types of submarine landslides, i.e., creeps, slumps, and landslide complexes, are recognized. These landslides are mostly distributed in the head areas and on the flanks of the canyons. As the most widespread landslides in the region, creeps are usually composed of multiple laterally-coalesced creep bodies, in which the boundaries of singular component creep bodies are difficult to delineate. In addition, a total of 77 landslides are defined, including 61 singular slumps and 16 landslide complexes that consist of two or more component landslides. Statistics show that most landslides are of a small dimension (0.53–18.09 km² in area) and a short runout distance (less than 3.5 km). Regional and local slope gradients and rheological behavior of the displaced materials might play important roles in the generation and distribution of the submarine landslides. A conceptual model for the co-evolution of the canyons and the associated landslides in the study area is presented. In the model it is assumed that the canyons are initiated from gullies created by landslides on steeper sites of the continental slope. The nascent canyons would then experience successive retrogressive landsliding events to extend upslope; at the same time canyon downcutting or incision would steepen the canyon walls to induce more landslides. 相似文献
18.
Claudio Lo Iacono Attilio Sulli Mauro Agate Valeria Lo Presti Fabrizio Pepe Raimondo Catalano 《Marine Geophysical Researches》2011,32(1-2):127-138
The continental shelf and the upper slope of the Gulf of Palermo (Southern Tyrrhenian Sea) in the depth interval ranging from 50 to 1,500 m were mapped for the first time with Multi Beam echosounder and high resolution seismic. Seven submarine canyons are confined to the upper slope or indent the shelf-edge and enter the Palermo intraslope basin at a depth of around 1,300 m. The canyons evolved through concurrent top-down turbiditic processes and bottom-up retrogressive mass failures. Most of the mass failure features of the area are related to canyon-shaping processes and only few of them are not confined to the upper slope. In general, these features probably do not represent a significant tsunami hazard along the coast. The geological element that controls the evolution of the canyons and induces sediment instability corresponds to the steep slope gradient, especially in the western sector of the Gulf, where the steepest canyons are located. The structural features mapped in the Palermo offshore contributed to the regulation of mass failure processes in the area, with direct faults and antiform structures coinciding with some of the canyon heads. Furthermore, the occurrence of pockmarks and highs that probably consist of authigenic carbonates above faulted and folded strata suggests a local relationship between structural control, fluid escape processes and mass failure. This paper presents a valuable high-resolution morphologic dataset of the Gulf of Palermo, which constitutes a reliable base for evaluating the geo-hazard potential related to slope failure in the area. 相似文献
19.
Two fundamentally different types of submarine canyons along the continental margin of Equatorial Guinea 总被引：1，自引：0，他引：1
Most submarine canyons are erosive conduits cut deeply into the world’s continental shelves through which sediment is transported from areas of high coastal sediment supply onto large submarine fans. However, many submarine canyons in areas of low sediment supply do not have associated submarine fans and show significantly different morphologies and depositional processes from those of ‘classic’ canyons. Using three-dimensional seismic reflection and core data, this study contrasts these two types of submarine canyons and proposes a bipartite classification scheme.The continental margin of Equatorial Guinea, West Africa during the late Cretaceous was dominated by a classic, erosional, sand-rich, submarine canyon system. This system was abandoned during the Paleogene, but the relict topography was re-activated in the Miocene during tectonic uplift. A subsequent decrease in sediment supply resulted in a drastic transformation in canyon morphology and activity, initiating the ‘Benito’ canyon system. This non-typical canyon system is aggradational rather than erosional, does not indent the shelf edge and has no downslope sediment apron. Smooth, draping seismic reflections indicate that hemipelagic deposition is the chief depositional process aggrading the canyons. Intra-canyon lateral accretion deposits indicate that canyon concavity is maintained by thick (>150 m), dilute, turbidity currents. There is little evidence for erosion, mass-wasting, or sand-rich deposition in the Benito canyon system. When a canyon loses flow access, usually due to piracy, it is abandoned and eventually filled. During canyon abandonment, fluid escape causes the successive formation of ‘cross-canyon ridges’ and pockmark trains along buried canyon axes.Based on comparison of canyons in the study area, we recognize two main types of submarine canyons: ‘Type I’ canyons indent the shelf edge and are linked to areas of high coarse-grained sediment supply, generating erosive canyon morphologies, sand-rich fill, and large downslope submarine fans/aprons. ‘Type II’ canyons do not indent the shelf edge and exhibit smooth, highly aggradational morphologies, mud-rich fill, and a lack of downslope fans/aprons. Type I canyons are dominated by erosive, sandy turbidity currents and mass-wasting, whereas hemipelagic deposition and dilute, sluggish turbidity currents are the main depositional processes sculpting Type II canyons. This morphology-based classification scheme can be used to help predict depositional processes, grain size distributions, and petroleum prospectivity of any submarine canyon. 相似文献
20.
The upper part of the continental slope in the northern South China Sea is prone to submarine landslide disasters,especially in submarine canyons. This work studies borehole sediments, discusses geotechnical properties of sediments, and evaluates sediment stability in the study area. The results show that sediment shear strength increases with increasing depth, with good linear correlation. Variations in shear strength of sediments with burial depth have a significantly greater rate of change in the canyon head and middle part than those in the canyon bottom. For sediments at the same burial depth, shear strength gradually increased and then decreased from the head to the bottom of the canyon, and has no obvious correlation with the slope angle of the sampling site. Under static conditions, the critical equilibrium slope angle of the sediments in the middle part of the canyon is 10° to 12°, and the critical slope angle in the head and the bottom of the canyon is 7°. The results indicate that potential landslide hazard areas are mainly distributed in distinct spots or narrow strips on the canyon walls where there are high slope angles. 相似文献