近岸大区域水波数学模型及其数值求解

从水波发展方程出发,导出了大区域缓坡水波数学模型,并采用交错网格系统下的有限差分法对该数学模型进行了数值求解,计算结果表明该数学模型在粗网格下也能得到与实验结果比较一致的结果,从而表明该模型可用于较大区域的水波问题.该模型具有编程简单、求解比较快速、经济的优点.     

俯冲板片形貌特征和活动大陆边缘演化体制的关系

当大洋板块向大陆板块下俯冲时,上覆板块的边缘可以以沟—弧—盆体制发育,也可以不发育弧后拉伸盆地．为什么同属上覆板块边缘但可以这二种完全不同的体制演化是现代地球科学研究的一个热点．本文在查阅大量最新文献的基础上认为造成这二种不同演化体制除了与俯冲作用的年代学特征有关外还可能主要与俯冲板片的形貌不同所导致局部地幔对流方式不一有关．由于俯冲的倾角,俯冲达到的最大深度以及俯冲板片在６７０ｋｍ上下地幔过渡带处保存的形态等因素不同,造成仰冲板块边缘之下软流圈对流方式不一．从而,造成弧体近陆一侧是否将发生岩石圈拉伸的动力学过程．     

BOOK REVIEWS

Book Reviewed in this article: The Vanishing Farmland Crisis, Critical Views of the Movement to Preserve Agricultural Land . John Baden Protecting Farmlands . Frederick R. Steiner and John E. Theilacker Ecological Effects of Fire in South African Ecosystems . Peter de V. Booysen and Neil M. Tainton Geography in China . Wu Chuanjun , Wang Nailiang , Lin Chao and Zhao Songqiao Resource Inventory and Baseline Study Methods for Developing Countries . Francis Conant , Peter Rogers , Marion Baumgardner , Cyrus Mc Kell , Raymond Dasmann, and Priscilla Reining Principles of Remote Sensing . Paul J. Curran Famine As A Geographical Phenomenon . Bruce Currey and Graeme Hugo The Suburban Squeeze: Land Conversion and Regulation in the San Francisco Bay Area . David E. Dowall Senses of Place . John Eyles Uneven Development and the Geographical Transfer of Value . D. K. Forbes and P. J. Rimmer Issues in Wilderness Management . Michael Frome Land-use and Prehistory in South-east Spain , The London Research Series in Geography 8. Antonio Gilman and John B. Thornes with Stephen Wise Regions in Question, Space, Development Theory and Regional Policy . Charles Gore The Colorado River: Instability and Basin Management . William L. Graf Hazardous Waste Sites: The Credibility Gap . Michael R. Greenberg and Richard F. Anderson Peasants, Subsistence Ecology, and Development in the Highlands of Papua New Guinea . Lawrence S. Grossman Silver Cities: The Photography of American Urbanization, 1839-1915 Peter B. Hales Silicon Landscapes . Peter Hall and Ann Markusen Remaking Ibieca: Rural Life in Aragon under Franco . Susan F. Harding The European Energy Challenge: East and West . George W. Hoffman The Global Climate . John T. Houghton The Urban Jobless in Eastern Africa . Abel G. M. Ishumi . The Tourist: Travel in Twentieth-Century North America . John A. Jakle City and Society: An Outline for Urban Geography . R. J. Johnston Residential Segregation, The State and Constitutional Conflict in American Urban Areas . R. J. Johnston Accessibility and Utilization: Geographical Perspectives on Health Care Delivery . Alun E. Joseph and David R. Phillips To the Heart of Asia: The Life of Sven Hedin . George Kish North American Culture , Vol 1. Ary J. Lamme III Past and Present in the Americas: A Compendium of Recent Studies . John Lynch Ethnicity in Contemporary America: A Geographical Appraisal . Jesse O. Mc Kee The Shell Countryside Book . Richard Muir and Eric Duffey 1990 Planning Conference Series. Proceedings of the National Geographic Areas Conference . Proceedings of the Regional Geographic Areas Conferences Wood, Brick, and Stone: The North American Settlement Landscape . Vol. 2: Barns and Farm Structures . Allen G. Noble Bangladesh: Biography of a Muslim Nation . Charles Peter O'donnell     

Differential equations governing slip-induced pore-pressure fluctuations in a water-saturated granular medium

Macroscopic frictional slip in water-saturated granular media occurs commonly during landsliding, surface faulting, and intense bedload transport. A mathematical model of dynamic pore-pressure fluctuations that accompany and influence such sliding is derived here by both inductive and deductive methods. The inductive derivation shows how the governing differential equations represent the physics of the steadily sliding array of cylindrical fiberglass rods investigated experimentally by Iverson and LaHusen (1989). The deductive derivation shows how the same equations result from a novel application of Biot's (1956) dynamic mixture theory to macroscopic deformation. The model consists of two linear differential equations and five initial and boundary conditions that govern solid displacements and pore-water pressures. Solid displacements and water pressures are strongly coupled, in part through a boundary condition that ensures mass conservation during irreversible pore deformation that occurs along the bumpy slip surface. Feedback between this deformation and the pore-pressure field may yield complex system responses. The dual derivations of the model help explicate key assumptions. For example, the model requires that the dimensionless parameterB, defined here through normalization of Biot's equations, is much larger than one. This indicates that solid-fluid coupling forces are dominated by viscous rather than inertial effects. A tabulation of physical and kinematic variables for the rod-array experiments of Iverson and LaHusen and for various geologic phenomena shows that the model assumptions commonly are satisfied. A subsequent paper will describe model tests against experimental data.     

Flood hydrograph estimation from arid catchment morphology

Data on performance of a geomorphologic rainfall-runoff model in simulating observed flash flood hydrographs in 32 arid catchments have been analysed. The catchments, which are located in the southwest region of Saudi Arabia, vary in their size, slope of land, and characteristics of soils, and are in zones of different rainstorm characteristics. The sensitivity of the model accuracy with various catchment and rainfall characteristics has been investigated. Size, followed by rate of infiltration and slope of land, are the most effective catchment characteristics affecting the accuracy. In addition, the accuracy varies with spatial and temporal rainfall variation, total rainfall depth, and length of the dry period between two successive rainstorms over catchment. It is sensitive to temporal rainfall variation more than spatial rainfall variation, and to the dry period more than total rainfall depth. Generally, the model did not display an accuracy approaching that of the observations, especially in simulating peak flowrates in large size infiltrating catchments having high temporal rainstorm variation. Guidelines on the best use of the model in arid catchments were proposed.     

页岩油藏多段水平井压后关井阶段压力扩散数学模型研究

多段多簇水平井压裂技术作为页岩油藏的重要开发手段已经得到了广泛认同,压后关井能充分发挥渗吸的作用,提高单井压后产量,但目前压裂液渗吸作用区域一直是困扰油藏工程师的重要难题。本文以陇东页岩油藏多段压裂井为研究对象,基于物质平衡原理,利用渗流力学和岩石力学理论,建立了压裂施工过程中和压后关井过程中流体压力扩散数学模型,研究了压力扩散和压裂液波及体积随时间的变化关系。结果表明：压裂液波及体积随关井时间的增加逐渐增加,但增加的幅度会逐渐降低。储层渗透率越小,孔隙度越大,压裂施工时间越长,关井阶段井底压力越高,地层能量越高。该结果可为页岩油藏最佳关井时间的确定提供理论支持。     

广西泗顶铅锌矿床矿体形貌特征及构造成因分析

研究矿体形貌分类,鉴别控制矿体的成矿构造类型,是成矿构造研究与预测的基础性工作,在矿山深部找矿工作中具有指导意义。广西泗顶铅锌矿床是桂北铅锌成矿区中大型矿床的典型代表,经过多年开采,其矿体的三维形貌已展露无遗,具有进行矿体形貌及构造成因研究的良好条件。基于矿体形貌视角,通过矿体形貌的几何特征及成因特征解析,建立矿体的构造成矿模式,分析讨论矿床的构造成因与动力学背景。研究结果表明：①泗顶矿区成矿构造类型分为两类,一类为早期构造流体型成矿构造,控制脉状铅锌矿体;另一类为晚期构造型成矿构造,控制蚀变岩型贫矿体,并叠加于早期脉状矿体之上。②矿体形貌由NE向右行张扭性断层控制形成的构造顺层脉型、NW向右行张性断层控制形成的构造切层脉型和脆–韧性剪切带控制形成的构造–流体型3种矿体形貌组成。基于矿体形貌建立以Ⅰ、Ⅳ号矿体为代表的构造顺层式成矿模式和以Ⅴ号矿体代表的构造切层式成矿模式。③区域动力学表明,泗顶矿区经历了多期构造运动,尤其是印支期的两次动力转换（早期SE向区域挤压力转换为EW向右行走滑剪切,晚期近EW向右行剪切则转换为EW向挤压）,为矿床的形成提供了优越的动力条件。④矿田动力学分析认为,泗顶铅锌成矿作用发生在脆–韧性剪切带演化到脆性阶段,应力弱化、变形分解、递进变形、非共轴剪切和层间滑动共同控制了各类几何矿体形貌的形成。     

突发性水污染扩散模型及其在GIS平台中的可视化

提出了一种适用于河流突发性水污染应急处理的工程化模型,采用四点隐式差分格式进行模型的数值求解,并在ArcGIS平台上实现了污染计算结果的实时动态可视化。最后,通过实例验证了该模型在公共安全应急平台中应用的有效性和合理性。     

三维激光扫描技术与断层面形貌量化分析在基岩区古地震研究中的应用

由于对第四纪地层的严重依赖,传统古地震探槽研究方法在基岩区难以发挥作用,导致无法获取基岩区断层的强震活动历史。本研究以山西地堑系的交城断裂为目标断裂,以断裂北段2处基岩断层面为研究对象,通过三维激光扫描技术获取基岩断层面高精度形貌,基于变差函数法结合滑动窗口操作量化断层表面形貌特征,开展在基岩区提取断裂古地震信息的实例研究。结果显示,2处基岩断层面的形貌在高度上具有明显的分段特征,指示了断层面在地震事件作用下的分段出露过程。这种断层面形貌分段特征可以用来识别古地震事件和同震位移量。在思西村基岩断层面上,识别出由老到新的3次古地震事件,同震倾滑位移量依次为2.0 m、1.9 m和2.3 m,在上兰镇基岩断层面上,识别出由老到新的3次古地震事件,同震倾滑位移量依次为1.4 m、2.5 m和2.0 m,指示了交城断裂北、中段具有产生同震位移量大于2 m、震级大于7.5级的破裂型地震的能力。上述研究成果表明,基于三维激光扫描和形貌量化分析方法开展基岩断层面古地震研究,可以准确而高效地识别古地震事件次数和同震位移量,扩展古地震的研究对象,拓宽古地震的研究空间。在未来的研究中,可以适时地开展宇宙成因核素测年以测定断层面的暴露年龄,获得发震年代,给予地震序列年龄框架。     

Channel processes following land use changes in a degrading steep headwater stream in North Island, New Zealand

In headwater streams in steep land settings, narrow and steep valley floors provide closely coupled relationships between geomorphic components including hillslopes, tributary fans, and channel reaches. These relationships together with small catchment sizes result in episodic changes to the amount of stored sediment in channels. Major sediment inputs follow high magnitude events. Subsequent exponential losses via removal of material can be represented by a relaxation curve. The influence of hillslope and tributary processes on relaxation curves, and that of altered coupling relations between components, were investigated along a 1.3 km reach of a degrading channel in the 4.8 km² Weraamaia Catchment, New Zealand. Extensive deforestation in the late 19th and early 20th centuries, followed by invasion of scrubs and reforestation, induced changes to major erosion types from gully complexes to shallow landslides. Changes in the size and pattern of sediment slugs from 1938 to 2002 were analysed from air photographs tied to detailed field measurement. The rate and calibre of sediment flux changed progressively following substantive hillslope input in a storm in 1938. Subsequently, the channel narrowed and incised, decoupling tributary fans from the main stem, thereby scaling down the size of sediment slugs. As a consequence, the dominant influence on the behaviour of sediment slugs and associated relaxation processes, changed from tributary fans to the type and distribution of bedrock outcrops along the reach.