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411.
Destructive tsunamis are infrequent comparedwith other natural disasters, andtheir evidences tend to disappear quickly.Conventional data acquisition havebeen limited in coverage and tend to beunreliable. Readily available andtransient data should be collectedby field survey teams as soon as possible.Since tsunamis are always triggered by the simultaneous or in-advanceoccurrence of another phenomena, they can be considered close to thesource as a syndrome, leaving a variety of almost simultaneous effectsat the nearby coasts. By observating the evidence left bythese local interaction effects, the surveyors should be able to identifyand evaluate at least the maximum horizontal extension and the verticalreach of the inundation. High water marks and lines of landward limitof sea grass, debris or sediment deposited, may help in this identification and measurement process.Guidelines to conduct post-tsunami field surveys and standards for theobservations have been established by the International Coordination Groupfor the Tsunami Warning System in the Pacific (ICG/ITSU) upon agreement with the scientific community. A Post-Tsunami Survey Field Guide was published by the Intergovernmental Oceanographic Commission (IOC) of UNESCO. 相似文献
412.
Mary E. Edwards Nancy H. Bigelow Bruce P. Finney Wendy R. Eisner 《Journal of Paleolimnology》2000,24(1):55-68
We investigated whether techniques developed to evaluate qualitative lake-level changes in the temperate zone can be used in sub-arctic and arctic Alaska. We focused on aquatic pollen records and sediment properties (loss-on-ignition and magnetic susceptibility) from centrally-located sediment-surface samples and cores, as these are the most commonly reported data in the literature. Modern aquatic pollen values are generally low (< 5%) and may be zero, even in lakes with abundant aquatic macrophytes. Greater diversity and higher values of aquatic pollen are likely at depths < 5 m, but pollen is found in depths up to 15 m. It is absent at depths > 20 m. Spores of Isoetes and Equisetum and Pediastrum cell-nets, when present, tend to be widely distributed, even in deep water. At Birch Lake, interior Alaska, trends in aquatic taxa and sediment characteristics for the last ca. 12,000 14C yrs recorded in a single, deep-water core reflect the same water-level changes as do transect-based lake-level reconstructions - if modern distributional characteristics of pollen and spores are taken into account. The lake rose from extremely low levels at ca. 12,000 14C yr B.P. After a period of fluctuation, it rose to a relatively high level by ca. 8000 14C yr B.P. and then stabilized. A preliminary survey of aquatic pollen trends from other lake-sediment records suggests that the period ca. 11,000-8000 14C yr B.P. may have seen relatively low lake levels in north-western and interior Alaska and high levels thereafter. Changes in aquatic pollen and sediments are evident in north-eastern interior lakes at the same time, but they are more difficult to interpret. Aquatic pollen productivity in Alaskan lakes may partly depend on factors other than water depth (e.g. temperature, pH, nutrient status, or length of the ice-free season). An Alaska-wide reconstruction of late-Quaternary lake levels based on extant single-core data would be best done after further study of contributing factors that may control sediment properties and aquatic pollen distribution. 相似文献
413.
区域旅游地理层次与人造景点之创意策划--回顾陈传康教授地段地理学思想 总被引:1,自引:0,他引:1
在简述人造景点之必然与存在问题的前提下,以区域旅游层次学观点论述了人造景点策划的地理环境问题. 相似文献
414.
The concentration levels of 12 priority volatile organic compounds (VOCs) were determined in two species of vertebrates and four species of invertebrates from sampling stations in the southern North Sea, using a modified Tekmar LSC 2000 purge and trap system coupled to gas chromatograph–mass spectrometer (GC–MS). In general, concentration levels of VOCs found in this study were of the same order of magnitude as those previously reported in the literature. The concentrations of the chlorinated hydrocarbons (CHCs), with the exception of chloroform, tended to be lower than those of the monocyclic aromatic hydrocarbons (MAHs). The experimental data were statistically evaluated using both cluster analysis and principal component analysis (PCA). From the results of cluster analysis and PCA, no specific groups could be distinguished on the basis of geographical, temporal or biological parameters. However, based on the cluster analysis and the PCA, the VOCs could be divided into three groups, C2-substituted benzenes, CHCs and benzene plus toluene. This division could be related to different types of sources. Finally, it was shown that organisms can be used to monitor the presence of VOCs in the marine environment and the observed concentrations levels were compared with proposed safety levels. 相似文献
415.
MicroStation环境下地图矢量数据全要素符号化研究 总被引:3,自引:0,他引:3
MicroStation是进行地图生产的图形编辑平台。把地图矢量数据在MicroStation中进行全要素符号化是实现其地图生产出版的首要条件。文中就符号化的各项工作进行了全面的论述 ,内容包括属性编码研究 ,符号库建立 ,分层规定 ,符号化控制表定义等 ,最后通过MDL编程实现了地图全要素的符号化。 相似文献
416.
417.
介绍了逐层子空间迭代法的基本原理及实现步骤,通过实例计算,与普遍迭代法对比,体现该算法的显著特点及其有于水文地质数值计算的可行性。 相似文献
418.
中国部分清洁地区大气中N2O的浓度 总被引:11,自引:0,他引:11
1993年4月—1995年8月对中国部分清洁地区大气的N2O浓度进行了现场观测,结果表明:农田(玉米田和麦田)大气的N2O平均浓度高达322.1-343.4ppbv,这是土壤排放N2O的结果;临安、龙风山和瓦里关山大气本底观测站(WMO/GAW)N2O的平均浓度分别为318.8±8.4ppbv,317.4±4.7ppbv和314.0±4.2ppbv。在此基础上,分析了大气N2O的分布及变化特征。另外,还对现场取样及N2O浓度测量技术作了初步分析和评价 相似文献
419.
N. P. Kurian K. Rajith B. T. Murali Krishnan N. Nirupama T. S. Murty 《Marine Geodesy》2006,29(4):277-281
During the Indian Ocean tsunami of December 26, 2004, specific observations were made by our survey team about the arrival times of several tsunami waves, their amplitudes, maximum extent of horizontal inundation on land and initial withdrawal of the ocean. Here the observations on the horizontal inundation and initial withdrawal are presented and briefly discussed. 相似文献
420.
Standardized diet compositions and trophic levels of sharks 总被引:13,自引:3,他引:13