Some Insights into Topographic,Elastic and Self-gravitation Interaction in Modelling Ground Deformation and Gravity Changes in Active Volcanic Areas     

María Charco  José Fernández  Francisco Luzón  Kristy F. Tiampo  John B. Rundle 《Pure and Applied Geophysics》2007,164(4):865-878

Surface displacements and gravity changes due to volcanic sources are influenced by medium properties. We investigate topographic, elastic and self-gravitation interaction in order to outline the major factors that are significant in data modelling. While elastic-gravitational models can provide a suitable approximation to problems of volcanic loading in areas where topographic relief is negligible, for prominent volcanoes the rough topography could affect deformation and gravity changes to a greater extent than self-gravitation. This fact requires the selection, depending on local relief, of a suitable model for use in the interpretation of surface precursors of volcanic activity. We use the three-dimensional Indirect Boundary Element Method to examine the effects of topography on deformation and gravity changes in models of magma chamber inflation/deflation. Topography has a significant effect on predicted surface deformation and gravity changes. Both the magnitude and pattern of the geodetic signals are significantly different compared to half-space solutions. Thus, failure to account for topographic effects in areas of prominent relief can bias the estimate of volcanic source parameters, since the magnitude and pattern of deformation and gravity changes depend on such effects.  相似文献   

Morphology of the Itapeva to Tramandai transgressive dunefield barrier system and mid‐ to late Holocene sea level change     

Patrick A. Hesp  Sergio Rebello Dillenburg  Eduardo Guimaraes Barboza  Luiz C. P. Clerot  Luiz J. Tomazelli  Ricardo Norberto Ayup Zouain 《地球表面变化过程与地形》2007,32(3):407-414

The surface morphology of the transgressive dunefield barrier extending from Itapeva to Tramandai along the northern littoral of Rio Grande do Sul, is examined and an attempt is presented to link morphological changes across the barrier to Holocene sea level changes. The 4·5 km wide Holocene barrier displays two typical morphologies: an inner part dominated by large‐scale, continuous alongshore, overlapping dunefield phases comprising sand sheets, dunes, deflation plains and precipitation ridges; and an outer part dominated by discontinuous, medium‐ to small‐scale, triangular to lobate transgressive dunefield phases, cut by both active and relict (palaeo‐) creeks or washouts. Holocene sea level in the region rose to c. +1 to +3 m above present reaching a maximum around 5100 years bp and then progressively fell to the present level. We argue that the effect on barrier development was to suppress the development of a drainage system during the rising and maximum stages, and encourage the development of an organized drainage system in the form of regularly spaced washouts during the falling period, and that this change in sea level from rising to falling therefore produced the large‐scale differences in barrier morphology. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

In situ measurements of surficial mud strength: A new vane tester suitable for soft intertidal muds     

P. Bassoullet  P. Le Hir 《Continental Shelf Research》2007

A vane fitted to a standard shear vane tester is described, the purpose of which is to obtain better measurements of the rheological properties of soft, surficial, intertidal muds (and consequently, variations in their erodability). Specifications and geometry of this vane are presented. The computation procedure is detailed, so that the methodology can be applied to any vane tester. The main improvement is a greater vertical resolution, typically less than 1 cm. Sets of direct measurements with this equipment and correlation with dry densities for three intertidal mudflats (estuaries and bay) are presented.  相似文献   

农业生产对气候变化的脆弱性研究方法初探   总被引：13，自引：1，他引：13  

刘文泉 《南京气象学院学报》2002,25(2):214-220

在总结脆弱性的定义与介绍相关研究方法的基础上，提出了农业生产对气候变化的脆弱性的初步定义、研究思路、指标体系及计算方法，并讨论了区域农业生产对气候变化影响的适应对策应遵循的有关原则。  相似文献   

Shape Similarity measures of Linear Entities     

ZhangQiaopin  LIDeren 《地球空间信息科学学报》2002,5(2):62-67

The essential of feature matching technology lies in how to measure the similarity of spatial entities.Among all the possible similarity measures,the shape similarity measure is one of the most important measures because it is easy to collect the necessary parameters and it is also well matched with the human intuition.In this paper a new shape similarity measure of linear entities based on the differences of direction change along each line is presented and its effectiveness is illustrated.  相似文献   

图幅磁偏角自动计算的原理和方法   总被引：2，自引：0，他引：2  

王双亭  王明孝等 《测绘学院学报》2002,19(2):122-123,127

详细论述了磁偏角自动计算的原理，并提出了一种利用地磁图自动计算图幅磁偏角的新方法，实验表明，用地磁图建立磁偏角数字模型和年变率数字模型进行图幅磁偏角的自动计算是可行的。  相似文献   

新疆库车盆地吉迪克组的地层时代和沉积环境   总被引：3，自引：0，他引：3  

关绍曾  关世桥 《化工矿产地质》2002,24(1):1-6,22

库盆地吉迪组分布十分广泛,它是储油层和油、气田的盖层,主要由碎屑岩或碎屑岩与石膏岩的互层组成,沉积厚度301.4-1081m。这套地层中富含有孔虫、介形类、抱粉、轮藻和腹足类等化石,通过古生物群的分折研究,可确定其沉积时代为中新世,更确切地说为中新世早、中期。通过沉积物特征和古生物群中广海、底栖有孔虫,咸水型介形类,水生植物抱粉和沟鞭藻等门类的分析,大致可确定沉积物的物源主要来自盆地北部的南天山山脉。沉积物颗粒自北向南由粗变细,水体中的含盐度自西向东逐渐升高,沉积了石膏、石盐和钙芒硝等盐类物质;推测在中新世早、中期库车盆地可能与塔里木盆地西部的喀什-乌恰-带残留海相连通。  相似文献   

温室效应变化及其地理意义   总被引：2，自引：0，他引：2  

王忠仁  郭有平  高自强 《世界地质》2002,21(3):278-282

在过去100年间，全球平均气温上升0．3－0．5℃，这种增温幅度与温度效应的预报结果相一致。也与气候变化的自然幅度相一致，由于温室气体效应，现代的气候变化与过去气候变化已有本质不同，经过进一步研究，多数科学家认为，全球变暖主要是大气中的温室气体增加造成的，温室效应变化具有重要的地理意义，增温幅度存在普遍适应的规律。冬季大于夏季，高纬度大于低纬度，陆地大于海洋。植物种群的更新及迁移可能跟不上气候变化的步伐，土壤的形成更将远远落后于气候变化，过渡带的生态系统将长时期内存在，它们将是不稳定的，脆弱的，物种的灭绝速度可能会因此加快，人类对生物资源的利用也许会面临新的问题和挑战。  相似文献   

环境中的多环芳烃及其生物恢复技术   总被引：9，自引：0，他引：9  

李志萍  陈肖刚  陈爱玖  马生明 《世界地质》2002,21(4):358-363

多环芳烃是一大类广泛存在于环境中的有机污染物。天然燃烧、火山爆发、矿物资料及其它有机物的不完全燃料和热解产生的PAH进入大气中，气态沉降、城市地表径流、城市污水、废水及油的溢涵和渗漏等是PAH进行地表水的主要途径，大气中PAH的干、湿沉降，污水灌溉，地面及地下储油装置的渗漏，地面固体废物堆的淋滤等是土壤中PAH的主要来源，沉积物和土壤是PAH的主要环境归宿。生物恢复是一种处理有机污染的新方法。  相似文献   

层次分析法在水环境系统工程中的应用   总被引：20，自引：0，他引：20       下载免费PDF全文

金菊良  魏一鸣  付强  丁晶 《水科学进展》2002,13(4):467-472

针对层次分析法中判断矩阵的一致性问题,直接从判断矩阵的定义出发,提出了基于加速遗传算法的层次分析法 (AGA-AHP),利用该法可同时确定层次各要素的相对重要性的排序权值和进行判断矩阵的一致性检验。理论分析和实例分析的初步结果说明:AGA-AHP法直观、可行且有效,计算简便、精度高。  相似文献