线性相关“可传递性”的几何意义

从几何角度对随机变量显著相关可传递性质进行了分析,得出了样本容量为n(n≥3)随机变量显著相关可传递性质的概率的几何表达式。用Monte-Carlo方法验证了几何分析的合理性,并对此问题展开了一定的讨论。     

结合投影变换和相位相关的海冰运动监测

为提高对渤海海冰旋转和平移运动的监测精度,提出一种基于投影变换的相位相关跟踪方法。选取连续8景静止水色成像仪(GOCI)图像序列,根据特征图像窗口的投影变换构造辅助函数,通过寻求函数最优解得到旋转角度集合,选择修正相关系数确定最佳旋转角度,同时根据相位信息实现海冰样本间亚像素级别的平移跟踪,消除传统相位相关法中因忽略图像相频特性所造成的匹配误差。实验结果表明,以手动测量的旋转角度为基准,该方法和传统相位相关法的旋转监测均方根误差的最大值/平均值分别为0.59/0.50与1.41/0.94,跟踪速度提高了50.6%;海冰平移运动的速度矢量与辽东湾的现场实测数据及历史资料记录数据基本一致。该方法对渤海海冰旋转和平移运动具有较好的跟踪效果。     

盾构施工参数与沉降变形关系模型构建

针对盾构施工参数变化对施工引起的地表变形的重要影响,该文构建了盾构施工参数与地表沉降变形关系模型。以北京市某地铁盾构区间施工过程中的实测数据为基础,分析了不同盾构施工参数与地表沉降变形的关联度和相关性,得到不同参数对沉降变形贡献值的大小;之后,利用多元回归模型方法建立主要影响参数与地表变形的关系模型,并进行模型的合理性检验;最后,利用该模型得到的沉降量与实测数据进行对比分析,结果显示符合性较好。     

倾斜摄影测量的城市真三维模型构建方法

针对如何基于近年来新推出的倾斜摄影测量技术快速构建城市真三维模型的问题,在研究分析国内基于该技术构建三维模型方法的基础上,提出了利用Street Factory系统,结合少量人工干预快速构建城市真三维模型的方法。采用倾斜影像联合空中三角测量技术,实现了多角度倾斜影像的一体化区域网平差;通过多视影像密集匹配和自动纹理关联,实现了高精度真实三维模型的构建。基于RCD-30倾斜相机获取的西安大雁塔景区倾斜影像,开展城市真三维模型构建试验。结果表明,所提方法构建的城市真三维模型满足相关规范的要求,适合大规模区域城市三维模型快速构建,对测绘生产单位规模化生产具有一定的参考价值。     

The Carrancas Formation,Bambuí Group: A record of pre-Marinoan sedimentation on the southern São Francisco craton,Brazil

The Carrancas Formation outcrops in east-central Brazil on the southern margin of the São Francisco craton where it comprises the base of the late Neoproterozoic Bambuí Group. It is overlain by the basal Ediacaran cap carbonate Sete Lagoas Formation and was for a long time considered to be glacially influenced and correlative with the glaciogenic Jequitaí Formation. New stratigraphic, isotopic and geochronologic data imply that the Carrancas Formation was instead formed by the shedding of debris from basement highs uplifted during an episode of minor continental rifting. Reddish dolostones in the upper Carrancas Formation have δ¹³C values ranging from +7.1 to +9.6‰, which is a unique C isotopic composition for the lowermost Bambuí Group but similar to values found in the Tijucuçu sequence, a pre-glacial unit in the Araçuaí fold belt on the eastern margin of the São Francisco craton. The stratigraphic position below basal Ediacaran cap carbonates and the highly positive δ¹³C values together indicate a Cryogenian interglacial age for the Carrancas Formation, with the high δ¹³C values representing the so-called Keele peak, which precedes the pre-Marinoan Trezona negative δ¹³C excursion in other well characterized Cryogenian sequences. Hence, The Carrancas Formation pre-dates de Marinoan Jequitaí Formation and represents an interval of Cryogenian stratigraphy not previously known to occur on the southern margin of São Francicso craton. Documentation of Cryogenian interglacial strata on the São Francisco craton reinforces recent revisions to the age of Bambuí Group strata and has implications for the development of the Bambuí basin.     

塔里木盆地麦盖提斜坡奥陶纪地层划分对比及意义

以碳同位素值的波动变化与沉积环境、海平面升降及地层界面突变等地质事件相对应为理论依据,开展碳同位素地层研究,建立了各组值域划分标准,解决碳酸盐岩地层缺乏标准生物化石情况下,地层归属难确定的问题。指出奥陶系自下而上碳同位素曲线呈现稳定-上升-正漂移的过程。其中,下统蓬莱坝组—鹰山组δ~(13)C值范围为(-4.2~-0.2)×10~(-3),始终为负值;中统一间房组δ~(13)C值范围为(-0.4~0.6)×10~(-3),以分布在零值附近为特征;上统恰尔巴克组—良里塔格组δ~(13)C值范围(0.7~3.1)×10~(-3),均为正值。在此基础上,开展了巴楚典型露头剖面与麦盖提斜坡井下奥陶系碳同位素地层与岩石地层对比研究,提出麦盖提斜坡中部及东部断洼区发育上奥陶统,除东部断裂带外,普遍残存下奥陶统顶部泥晶灰岩段。     

Interaction between trench retreat and Anatolian escape as recorded by neogene basins in the northern Aegean Sea

The evolution of the North Aegean Sea is studied through the development of three deep basins: the North Aegean Trough, the North Skyros Basin and the Ikaria Basin. Bathymetric data, a 2D seismic dataset and the well-investigated stratigraphic records of the onshore deep basins of northern Greece and Western Turkey were used to make structural and seismic stratigraphic interpretations. The study area shows two sharp unconformities that correspond to the Eocene-Oligocene transition and the Miocene-Pliocene shift. These discontinuities were used as marker horizons for a more detailed structural and seismic stratigraphic interpretation resulting in the identification of several seismic units. A general seismic signature chart was established using onshore basin stratigraphy and well data, which was then used to constrain the ages of the different seismic units. The main features observed in the basins are interpreted as: 1) trans-tensional growth patterns in Pliocene and Quaternary sediments that combine NE–SW trending and steeply dipping fault zones that likely correspond to strike-slip corridors and E-W/WNW-ESE trending normal faults, 2) regional erosional truncations of Miocene sediments, likely related to the Messinian Salinity Crisis (MSC), 3) thick delta-turbidite deposits of Neogene age. Only the North Aegean Trough shows evidence of earlier development and polyphase deformation through inversion structures, and additional seismic units. Extension processes in the Aegean region have been driven by the Hellenic slab rollback since the middle Eocene. The widespread development of Neogene basins at the whole Aegean scale attests to a major tectonic change due to an acceleration of the trench retreat in the middle Miocene. The present study shows that the Neogene basins of the North Aegean Sea developed in dextral transtension with the northward migration of the associated NE-SW trending strike-slip faults. At regional scale, this tectonic pattern indicates that the westward escape of Anatolia started to interact with the trench retreat in the middle Miocene, around 10 Myr before the arrival of the North Anatolian Fault in the North Aegean Sea.     

Three dimensional seismic studies of deep-water hazard-related features on the northern slope of South China Sea

Mass transport deposits and geological features related to fluid flow such as gas chimneys, mud diapirs and volcanos, pockmarks and gas hydrates are pervasive on the canyon dominated northern slope of the Pearl River Mouth basin of the South China Sea. These deposits and structures are linked to serious geohazards and are considered risk factors for seabed installations. Based on high resolution three dimensional seismic surveys, seismic characteristics, distributions and origins of these features are analyzed. A distribution map is presented and geometrical parameters and spatial distribution patterns are summarized. Results show that various groups of the mapped features are closely tied to local or regional tectonism and sedimentary processes. Mass transport complexes are classified as slides near the shelf break, initially deformed slumps on the flanks of canyons and highly deformed slumps on the lower slope downslope of the mouth of canyons. We propose them to be preconditioned by pore pressure changes related to sea level fluctuations, steep topography, and fluid and fault activities. Gas chimneys are mainly located in the vicinity of gas reservoirs, while bottom-simulating reflectors are observed within the gas chimney regions, suggesting gas chimneys serve as conduits for thermogenic gas. Mud diapirs/volcanos and pockmarks are observed in small numbers and the formation of pockmarks is related to underlying gas chimneys and faults. This study aims at reducing risks for deep-water engineering on the northern slope of South China Sea.     

Stratigraphic evolution of Eocene clinoforms from northern Santos Basin,offshore Brazil: Evaluating controlling factors on shelf-margin growth and deep-water sedimentation

In order to assess the controlling factors on the evolution of a shelf margin and the timing of sediment transfer to deep waters, a seismic stratigraphic investigation was carried out in the Eocene interval of northern Santos Basin, offshore Brazil. The studied succession configures a complex of prograding slope clinoforms formed in a passive margin and encompasses five seismic facies and their respective depositional settings: shelf-margin deltas/shorefaces, oblique slope clinoforms, sigmoidal slope clinoforms, continental to shelfal deposits and mass-transport deposits. These are stratigraphically arranged as seven depositional sequences recording a total shelf-edge progradation of about 35 km and a progradation rate of 1,75 km/My. Two main types of sequences can be recognized, the first one (type A) being dominated by oblique slope clinoforms and shelf-margin deltas/shorefaces in which shelf-edge trajectories were essentially flat to descending and extensive sandy turbidites were deposited on the foreset to bottomset zones. Sequences of this type are dominated by forced-regressive units deposited during extensive periods of relative sea-level fall. Type B comprises an upper part represented by aggradational shelfal deposits and a lower part composed of mass-transport deposits and high-relief sigmoidal clinoforms with descending shelf-edge trajectory. Steep slump scars deeply cut the shelfal strata and constitutes the boundary between the two intervals observed in type B sequences. Sandy turbidites occur at the same frequency in both forced- and normal-regressive units but are more voluminous within forced-regressive clinoforms associated with shelf-margin deltas/shorefaces. Major slope failures and mass-transport deposits, by the other hand, occurred exclusively in type B sequences during the onset of sea-level fall and their volume are directly related to the thickness of the shelfal sediments formed during the pre-failure normal regressions.     

Fracture characteristics in Cretaceous platform and overlying ramp carbonates: An outcrop study from Maiella Mountain (central Italy)

This article focuses on field- and laboratory-based characterization of vertically persistent fractures that are part of oblique-slip normal fault zones and crosscut the Cretaceous platform and overlaying ramp carbonates outcropping at Maiella Mountain (central Italy). The achieved results show that: (i) fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones; (ii) joints and sheared joints composing the fault damage zones are taller, better connected and less spaced within the former rocks than in the ramp carbonates. The aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure. At Maiella Mountain, platform carbonates are, indeed, made up of overall stiffer (higher Uniaxial Compressive Strength values) and less porous rocks, due to more abundant intergranular void-filling cement and presence of matrix.In terms of hydrocarbon flow and recovery, geometric and dimensional attributes of fractures suggest that the well-connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow. In contrast, the relatively poorly connected and low-density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons.