中国区域地壳稳定性定量化评价与分区   总被引：13，自引：1，他引：12  

孙叶  谭成轩  杨贵生  王瑞江 《地质力学学报》1997,3(3):41-52

中国地处环太平洋构造带与地中海构造带交接部位,地质构造复杂,活动性较为强烈,各种内动力地质灾害比较严重,总体看来中国区域地壳稳定性相对较差。为了使区域地壳稳定性评价与分区获得定量化认识,更好地服务于经济建设和减灾防灾,本文在分析中国现今活动的主要构造体系与内动力地质灾害的分布规律的基础上,首先进行区域地壳稳定性定量化评价待评区的划分;其次进行定量化评价指标的选定、取值、权重分配及评价标准的确定;最后运用模糊数学进行中国区域地壳稳定性定量化评价与分区。   相似文献   

两种形态ENSO对南半球热带外气候变化特征的影响          下载免费PDF全文

万伟杰张召儒  刘海龙周朦 钟贻森 《极地研究》2018,30(4):376-390

本研究利用1979—2012年欧洲中期天气预报中心(ECMWF)的ORAP5(Ocean Reanalysis Pilot 5)海洋/海冰再分析资料和ERA-Interim气象再分析资料,采用回归分析方法,分1979—1998年和1999—2012年两个时间段探讨了南半球热带外地区气候变化对两种不同形态ENSO的响应特征。结果表明,南半球热带外区域气候在1999年前后两个时段对ENSO的响应表现出了较大的年代际变化特征。1979—1998年南半球热带外气候变量对Nio3指数在时间上的相关性和空间上的响应强度都普遍大于Nio4指数,说明这一时段东部型ENSO对南半球热带外区域气候变化的影响要更强一些。在1999—2012年,不同形态ENSO与气候变量的相关性大小并无明显的规律,而且空间响应场的差异性并不大。海平面气压、风场和气温对ENSO变化的响应在南半球冬季表现最为强烈,在夏季最弱。三者在1999—2012年秋季对Nio3指数和Nio4指数的响应场中出现了纬向三波数结构。1999—2012年冬季,有异于海平面气压和风场,在罗斯海和阿蒙森海海域海表气温对Nio4变化的正响应明显强于对Nio3的响应,该特征在混合层温度中也有体现,表明海表气温随ENSO的变化受海洋特征变化影响较大。混合层深度和混合层温度的响应场之间存在很大的相关性,混合层温度响应在秋季表现最强,春季最弱,混合层深度响应与之相反。在1979—1998年,海冰密集度对不同Nio指数变化的响应差异主要出现在海冰结冰季节,而海冰厚度对不同Nio指数变化的响应差异在夏季表现较强。海冰密集度和厚度对Nio3变化响应的年代际差异在秋冬季节更加明显,对Nio4变化响应的年代际差异在秋、冬、春季都较明显。  相似文献   

Structuring factors of the spatio-temporal variability of macrozoobenthos assemblages in a southern Mediterranean lagoon: How useful for bioindication is a multi-biotic indices approach?     

Ines Khedhri  Ahmed Afli  Lotfi Aleya 《Marine pollution bulletin》2017,114(1):515-527

The authors investigated the impact of the extension of the El Kantra Channel on the composition and structure of macrobenthic assemblages in Boughrara Lagoon (Gulf of Gabes, Tunisia along with the use of 4 biotic indices (AMBI, BENTIX, M-AMBI and TUBI). Thirteen stations were sampled seasonally in 2012–2013. Forty-one species were found in 2012–2013 not recorded in 2009–2010, including 20 species of polychaetes belonging to the trophic groups of deposit-feeders and carnivores which are expected to increase in areas disturbed by organic pollution. During the survey, we recorded a high fish mortality, essentially caused by the development of harmful algal blooms (HAB) which increased organic matter deposition, thus inducing polychaete development. This seems to weaken the bio-indicating power of biotic indices used here which, paradoxically, classified all sampled stations at a high ecological status. A review of these indices and their applicability to all marine environments is recommended.  相似文献   

THE RESPONSE OF FLUVIAL GEOMORPHOLOGIC CHARACTERISTICS OF THE FUJIANG DRAINGE BASIN TO ACTIVITY OF THE HUYA FAULT ZONE     

LIANG Ou-bo  REN Jun-jie  L&#  Yan-wu 《地震地质》2018,40(1):42-56

The Huya Fault, located in the steep topographic boundary of the Minshan Mountains in the eastern margin of the Tibetan plateau, has documented many major earthquakes such as the 1630(M=6 3/4), 1973 Huanglong(M_S=6.5) and the 1976 Songpan-Pingwu earthquake swarm(M_S=7.2, 6.7, 7.2). While its activity remains unclear because of lacking Quaternary sediments. In the past few decades, there have been significant advances in understanding the relationship between bedrock channel landscapes and active tectonics, indicating that the bedrock fluvial features can well record the tectonic activity. Many studies reveal that tectonism is the primary factor of landscape evolution in tectonically active regions, and the erosional landscapes can be used to reveal tectonic signals on timescales of 10³~10⁶ years. The Huya Fault crosses the Fujiang drainage basin, making it suitable for the study of bedrock rivers and tectonic uplift in the eastern margin of Minshan. In this study, we calculate the geomorphologic indeices(hillslope, local relief, normalized steepness indices and hypsometric integral) on the basis of the digital elevation model(DEM) SRTM-1. For better understanding the tectonic activity along this fault, we derive some small catchments on the two sides of the Huya fault to analyze the differences of average steepness indices and hypsometric integral. Combining with field observations, lithology, precipitation and modern erosion rates, this study suggests that tectonic activity is the controlling factor of geomorphology in the eastern margin of the Minshan Mountains. We use focal mechanism solutions, GPS data and geomorphic evidence to explore the relationship between the geomorphologic indices of the Fujiang drainage and activity characteristics of the Huya fault. Our results suggest that:(1) The Fujiang drainage basin is in a steady state. The characteristics of the knickpoints indicate that they are mainly controlled by the locally resistant substrate. (2) The suggested value of the geomorphologic index on the west side of the Huya fault is generally larger than on the east side, showing differential tectonic uplift rates across the fault. (3) The difference of the geomorphologic index of the small catchments on both sides of the Huya fault is gradually increasing from north to south along this fault, in accordance with that the north and south segments of the Huya fault are dominated by strike-and reverse-slip, respectively.  相似文献   

多样性指数在海洋浮游植物研究中的应用   总被引：109，自引：12，他引：97  

孙军  刘东艳 《海洋学报》2004,26(1):62-75

对海洋浮游植物群落分析中常用的多样性指数进行了比较研究.对物种丰富度依赖型、丰度依赖型和实测浮游植物群落中物种丰富度、Shannon指数(以2或e为底)、Pielou均匀度指数、Simpson指数(1-D或1/D形式)、Margalef指数、Berger-Parker指数、McIntosh指数、McIntosh均匀度指数、Brillouin指数、Brillouin均匀度指数、Fisher α指数和Q统计指数等不同多样性指数计算结果进行了比较,发现不同多样性指数对浮游植物群落多样性的分析存在明显差异.对于一般情况下浮游植物群落多样性的研究,物种丰富度、Margalef指数、Fisher α指数、Shannon指数、Simpson相遇指数和Pielou指数的综合使用是较合适的,但对Margalef指数和Fisherα指数的结果要谨慎解释.并在综合应用各指数的基础上提出了浮游植物群落多样性分析的一般步骤.  相似文献   

Exploring hyperspectral bands and estimation indices for leaf nitrogen accumulation in wheat     

Xia Yao  Yan ZhuYongChao Tian  Wei FengWeiXing Cao 《International Journal of Applied Earth Observation and Geoinformation》2010

Hyperspectral sensing can provide an effective means for fast and non-destructive estimation of leaf nitrogen (N) status in crop plants. The objectives of this study were to design a new method to extract hyperspectral spectrum information, to explore sensitive spectral bands, suitable bandwidth and best vegetation indices based on precise analysis of ground-based hyperspectral information, and to develop regression models for estimating leaf N accumulation per unit soil area (LNA, g N m⁻²) in winter wheat (Triticum aestivum L.). Three field experiments were conducted with different N rates and cultivar types in three consecutive growing seasons, and time-course measurements were taken on canopy hyperspectral reflectance and LNA under the various treatments. Then, normalized difference spectral indices (NDSI) and ratio spectral indices (RSI) based on the original spectrum and the first derivative spectrum were constructed within the range of 350–2500 nm, and their relationships with LNA were quantified. The results showed that both LNA and canopy hyperspectral reflectance in wheat changed with varied N rates, with consistent patterns across different cultivars and seasons. The sensitive spectral bands for LNA existed mainly within visible and near infrared regions. The best spectral indices for estimating LNA in wheat were found to be NDSI (R₈₆₀, R₇₂₀), RSI (R₉₉₀, R₇₂₀), NDSI (FD₇₃₆, FD₅₂₆) and RSI (FD₇₂₅, FD₅₁₆), and the regression models based on the above four spectral indices were formulated as Y = 26.34x^1.887, Y = 5.095x − 6.040, Y = 0.609 e^3.008x and Y = 0.388x^1.260, respectively, with R² greater than 0.81. Furthermore, expanding the bandwidth of NDSI (R₈₆₀, R₇₂₀) and RSI (R₉₉₀, R₇₂₀) from 1 nm to 100 nm at 1 nm interval produced the LNA monitoring models with similar performance within about 33 nm and 23 nm bandwidth, respectively, over which the statistical parameters of the models became less stable. From testing of the derived equations, the model for LNA estimation on NDSI (R₈₆₀, R₇₂₀), RSI (R₉₉₀, R₇₂₀), NDSI (FD₇₃₆, FD₅₂₆) and RSI (FD₇₂₅, FD₅₁₆) gave R² over 0.79 with more satisfactory performance than previously reported models and physical models in wheat. It can be concluded that the present hyperspectral parameters of NDSI (R₈₆₀, R₇₂₀), RSI (R₉₉₀, R₇₂₀), NDSI (FD₇₃₆, FD₅₂₆) and RSI (FD₇₂₅, FD₅₁₆) can be reliably used for estimating LNA in winter wheat.  相似文献   

模糊物元理论在干旱分析中的应用研究     

冯星  孙东永  胡维登  张彤  郭建青 《水文》2018,38(6):18-23

干旱的评价指标具有多样性,各种指标在优劣程度上是渐变的,具有模糊性,不同的干旱指标对干旱的分析会存在一定的差异性。利用渭河流域1960～2010年近50a的日气候资料,通过分析计算选取标准降水指数、综合干旱指数和降水距平百分率并通过模糊物元理论将这三种干旱评价指标结合起来构建一种新的评价方法并与已发生的干旱进行分析对比。结果显示:模糊物元理论可以很好的将多种干旱指标结合起来从而减小不同指标分析所存在的差异性;且与单独一干旱指标所分析的干旱趋势没有出现较大的偏差。可以将多种分析方法结合起来更好的揭示干旱的变化规律,定量评价流域内的干旱变化情况,对抗旱减灾工作有重要的科学意义。  相似文献   

典型地貌景观指数的多尺度效应分析 ——以山西省运城市为例   总被引：2，自引：0，他引：2  

毕如田  高艳 《地球信息科学学报》2012,14(3):338-343

 景观指数作为定量描述景观特征的指数,具有明显的尺度效应。进行景观指数的尺度效应研究,对进一步理解格局与尺度之间的关系具有重要意义。本文以TM影像为基础,选择山西省运城市平原、丘陵、山地及综合地貌4种不同地貌类型,对7个常用景观指数进行了多尺度效应分析。结果表明:不同地形上斑块密度(PD)、景观形状指数(LSI)、结合度(COHESION)3个指数有明显的粒度效应,随粒度的增加呈现逐渐减少的变化趋势;最大斑块指数(LPI)、周长面积比分维数(PAFRAC)、景观聚集度(CONTAG)和Shannon多样性指数(SHDI)4个指数随粒度的增加几乎不发生变化。不同地貌的景观指数随幅度的变化规律比较复杂,景观形状指数(LSI)随幅度的增加呈现逐渐增加的趋势,其余6个指数在较小幅度范围内变化比较复杂,但随着幅度的增大有逐渐趋于平稳的趋势。针对研究区不同地貌类型,其景观指数在不同粒度和幅度下有较大区别,可以根据景观指数值的大小来区分地貌的复杂程度。  相似文献   

Adiabatic indices in a convecting anisotropic plasma     

M.I. Pudovkin  C.-V. Meister  B.P. Besser 《Astronomische Nachrichten》1999,320(2):87-93

Adiabatic indices for a non-dissipative anisotropic convecting plasma are analyzed, and general expressions for the effective adiabatic index and the partial adiabatic indices parallel (γ_∥) and perpendicular (γ_⟂) to the magnetic field are obtained. It is shown that, in the general case, the value of the effective adiabatic index is not an universal constant and depends on the plasma temperature anisotropy and on the properties of the plasma motion. The values of γ_⟂ and γ_∥ are shown to be independent of the plasma parameters being completely determined by the characteristics of the plasma flow.  相似文献   

Damage response of multistorey r/c buildings with different structural systems subjected to seismic motion of arbitrary orientation          下载免费PDF全文

Konstantinos Kostinakis  Konstantinos Morfidis  Hariton Xenidis 《地震工程与结构动力学》2015,44(12):1919-1937

In the present study the combined influence of seismic orientation and a number of parameters characterizing the structural system of Reinforced Concrete (R/C) buildings on the level of expected damages are examined. For the purposes of the above investigation eight medium‐rise buildings are designed on the basis of the current seismic codes. The structural characteristics examined are the ratio of the base shear received by the structural walls, the ratio of horizontal stiffness in two orthogonal directions and the structural eccentricity. Then, the buildings are analyzed by nonlinear time response analysis using 100 bidirectional earthquake ground motions. The two horizontal accelerograms of each ground motion are applied along horizontal orthogonal axes, forming 72 different angles with the structural axes. The structural damage is expressed in terms of the Park and Ang damage index. The results of the analyses revealed that the damage level of the buildings is strongly affected by the incident angle of the ground motion. The extent at which the orientation of the seismic records influences the damage response depends on the structural system and the distance of the record to the fault rupture. As a consequence, the common practice of applying the earthquake records along the structural axes can lead to significant underestimation of structural damage. Also, it was shown that the structural eccentricity can significantly differentiate the seismic damage level, as well as the impact of the earthquake orientation on the structural damage. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献