井孔水位记震能力变化与近大地震关系研究   总被引：7，自引：0，他引：7  

万登堡 《地震研究》1992,15(4):381-391

通过对云南省及邻近地区7级大震,震前群井水位记震能力变化的研究及异常、预报指标检验,表明震前记震能力减弱或消失与近大地震有关。其异常特征表现为形态相似、时间同步、幅度明显等特点。井孔水位记震能力变化可能是地下水中期预报地震的一种新方法。  相似文献   

基于道路交叉点邻域扩张曲线的城市边界识别——以成都、西安、武汉、南京和长沙为例     

林晓娟  房世峰  徐亚莉  邹宝裕  罗明良 《地理科学进展》2018,37(6):781-789

城市边界识别是定性和定量研究城市的基础和前提,已有的关于城市边界提取的研究大都需要提前设定阈值或依赖人口统计数据。基于分形几何学,利用矢量建筑物分布数据识别城市边界,虽可克服这一缺陷,但国内城市边界的研究往往受阻于矢量建筑物分布数据获取困难。本文提出了一种基于道路交叉点的邻域扩张曲线作为识别城市边界的新方法。结果表明：该方法以电子地图为数据源,基于道路交叉点矢量数据进行研究时,城市集群数据随搜索半径增大而改变,城市扩张曲线中的最佳距离阈值是提取城市边界的关键;提取成都、西安、武汉、南京和长沙城市边界的最佳距离阈值分别为133、114、139、124和129 m,各城市的集群面积分别为769、350、270、317和359 km²。利用道路交叉点提取城市边界,方法简便可行,数据较易获得,本文结论有望为城市形态发展演变和城市规划等相关研究提供参考。  相似文献   

From Planetary Boundaries to national fair shares of the global safe operating space — How can the scales be bridged?     

《Global Environmental Change》2016

The planetary boundaries framework proposes quantitative global limits to the anthropogenic perturbation of crucial Earth system processes, and thus marks out a planetary safe operating space for human activities. Yet, decisions regarding resource use and emissions are mostly made at less aggregated scales, by national and sub-national governments, businesses, and other local actors. To operationalize the planetary boundaries concept, the boundaries need to be translated into and aligned with targets that are relevant at these decision-making scales. In this paper, we develop a framework that addresses the biophysical, socio-economic, and ethical dimensions of bridging across scales, to provide a consistently applicable approach for translating the planetary boundaries into national-level fair shares of Earth’s safe operating space. We discuss our findings in the context of previous studies and their implications for future analyses and policymaking. In this way, we link the planetary boundaries framework to widely-applied operational and policy concepts for more robust strong sustainability decision-making.  相似文献   

Calibration studies concerning a one-dimensional numerical tidal model with particular reference to resistance coefficients     

Stephen G. Wallis  Donald W. Knight 《Estuarine, Coastal and Shelf Science》1984,19(5):541-562

Since the hydrodynamics of flow in most shallow estuaries is dominated by the boundary resistance, the selection of appropriate values for the roughness coefficients in any numerical tidal model is important. The paper describes studies involving the intra-tidal variation of resistance coefficients in twelve reaches of the Conwy estuary in North Wales. Resistance coefficients are evaluated for six water level data sets covering the neap to spring tidal variation by cubature based and parameter estimation techniques. Results from these two inverse methods are shown to agree well despite somewhat different schematizations for the estuary. A direct check on the intra-tidal variation of resistance coefficients at one particular reach is made possible by specifically gathered field data described in an earlier paper by Knight. In general the resistance coefficients exhibit three basic trends—a strong stage dependence, a flow directional dependence due to flood or ebb dominated bed forms, and a high variability with location along the estuary, especially where sand banks are oxposed at low water. The optimized resistance coefficients are then used in a one-dimensional numerical tidal model in order to ascertain the effect of particular modes of calibration. Estuary mean errors in water levels are of the order of 2,5 and 16 cm for the three calibrations tested.  相似文献   

Geological Characteristics and Manifestations of Geological Processes of Sequence Boundaries and Their Vicinities     

Xiao Linping Testing Centre of Geotechnical Engineering  Southwest Jiaotong Universityand Zhao YuguangChengdu Institute of Mineral Resources  Chinese Academy of Geological Sciences  Chengdu  Sichuan  Liu Xinzhu 《《地质学报》英文版》1997,71(4):386-394

This paper discusses the geological characteristics and architectures of sequence boundaries and their vicinities and has proposed a classification scheme for the sequence boundaries, which can thus be grouped into three types and eight categories: type I includes exposed truncated surface, palaeosol surface, palaeokarst surface and exposed surface; type Ⅱ boundaries include structural transitional surface during sea-level fall and transgressive onlap surface; and type Ⅲ includes submarine erosional diagenetic diastem and event surface. A study has been made for the three major boundaries lying between the Permian and pre-Permian, the Permian and Triassic, and the Middle and Lower Triassic respectively in terms of multiple disciplines such as lithostratigraphy, biostratigraphy, magnetostratigraphy and carbon and oxygen isotopic geology. These three boundaries are ascribed to type I , typeⅡ and typeⅢ, respectively.  相似文献   

Calcareous nannofossils and the Santonian/Campanian and Campanian/Maastrichtian boundaries on the Brazilian Continental Margin: historical overview and state of the art     

Armando Scarparo Cunha  Rogério Loureiro Antunes  Jackie A. Burnett 《Cretaceous Research》1997,18(6):823-832

Recognition of the Campanian stage on the Brazilian Continental Margin, using calcareous nannofossils, has been historically problematic. This paper constitutes an overview of earlier works, showing how nannofossil biostratigraphic ideas have evolved since Troelsen & Quadros provided the first biozonation of this region in 1971. Recent studied have provided data which have helped to clarify these apparent biostratigraphic problems, and allows this region to be placed in a global biostratigraphic context.The earliest researchers identified the Santonian/Campanian boundary by the last occurrences of ‘Lithastrinus grillii’ andPetrobrasiella venata. P. venatawas later abandoned as an index species due to its rarity and, instead, the last occurrences ofMarthasterites furcatusand ‘Lithastrinus grillii’ became the most-used markers. However, the stratigraphic age of these biohorizons diverged from those quoted in the literature. In the Brazilian basins, these extinctions, rather than having occurred in the Campanian as was recorded elsewhere, were considered to mark the top of the Santonian, as suggested by correlations with other microfossil groups (primarily foraminifera and palynomorphs). To explain this phenomenon, the existence of a condensed sequence was postulated for most of the Brazilian marginal basins, where the uppermost Santonian deposits were apparently indistinguishable from those of the lowermost Campanian. In line with current correlations presented in the nannofossil literature, and with new information obtained from core and side-wall samples, it is now believed that the extinction of these speciesdidoccur in the Campanian in the Brazilian basins, whilst the last occurrence ofLithastrinus moratus(previously misidentified asLithastrinus grillii) has become a useful Santonian marker. Thus the Santonian/Campanian boundary in Brazil lies in a stratigraphic position similar to elsewhere in nannofossil terms, that is below CC18.The Campanian/Maastrichtian boundary was initially characterised in nannofossil terms in Brazil by the last occurrence ofBroinsonia parca constricta, and later by the last occurrence ofEiffellithus eximius. Recently acquired data has shown that the sequence of events in the Brazilian marginal basins is similar to that of the Sissingh/Perch-Nielsen standard biozonation scheme through this interval. Again, correlations in the literature with the recently defined boundary (in macrofossil terms) thus allow the boundary to be determined between the last occurrences ofBroinsonia parca constrictaandUniplanarius trifidus, that is, in CC23b.  相似文献   

Wavefield downward extrapolation for migration velocity analysis on Marmousi data-set     

Andrzej Kostecki  Anna Półchłopek 《Acta Geophysica》2007,55(2):209-221

The authors present a method for estimation of interval velocities using the downward continuation of the wavefield to perform layer-stripping migration velocity analysis. The generalized, phase-shift migration MG(F-K) in wavenumber-frequency domain was used for fulltime downward extrapolation of the wavefield. Such downward depth extrapolation accounts for strong changes of velocity in lateral and vertical directions and helps in correct positioning of the wavefield image in complex structures. Determination of velocity is the recursive process which means that the wavefield on depth level z _n−1 (n = 0, 1, ...) is an input data-set for determination of velocity on level z _n . The velocity ν [x, z _n − z _n−1] can be thus treated as interval velocity in Δz _n = z _n − z _n−1 step. This method was tested on synthetic Marmousi data-set and showed satisfactory results for complex, inhomogeneous media.  相似文献   

利用表层模型的波场延拓基准面校正方案     

崔兴福  李宏兵  胡英  梁宏  齐莉 《应用地球物理》2007,4(2)

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THE NATURE‐CULTURE BOUNDARY AND OCEAN POLICY: GREAT BARRIER ISLAND,NEW ZEALAND*     

Janel M. Curry 《Geographical review》2007,97(1):46-66

ABSTRACT. This article analyzes New Zealand's rights‐based system of fisheries management from the perspective of local stakeholders on northern Great Barrier Island. The research identified differing perspectives through use of the concept of “boundary construction,” not only in terms of society and nature but also among societal institutions. Great Barrier Island participants exhibited significant differences, especially between staff of the local Department of Conservation and local Maori, both of whom were engaged in negotiating policy implementation at the local level. These differences expressed themselves in conceptions of both societal boundaries—the scale at which community was envisioned—and conceptions of the boundary between nature and culture. The findings confirm the need for the continued development of models of community‐based resource management as well as for the conceptual integration of society and nature in the realm of policy construction.  相似文献   

最优可分表示法三维波场延拓     

张致付  孟小红  刘洪  陈景波  李幼铭 《应用地球物理》2006,3(4):218-225

适于复杂介质的高精度波场延拓算子是叠前深度偏移研究的重要内容。本文采用最优可分表示方法,运用正反傅立叶变换构造了三维单程波场延拓算子,算子实现了波数域变量与空间(速度)域变量分离。波数域内进行相移计算,在空间域对因介质横向变速引起的时移作修正。脉冲响应显示在区域内各速度的脉冲计算值与理论值基本一致,说明最优可分表示法叠前深度偏移可适用于强变速条件下复杂介质的成像需求。SEG／EAGE模型和实测数据的成像结果验证了本文方法对复杂构造的成像能力。  相似文献