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This paper deals with the quality of two multivariate statistical models based on the Geographical Information System for
shallow landslide susceptibility assessment in a test area at La Pobla de Lillet (Eastern Pyrenees, Spain). The quality, which
was guaranteed by a rigorous methodology based on a suitable diagnosis, validation, and evaluation of the models, ensured
a reliable contrast of the final susceptibility maps. This enables us to transfer the best results to the end user. Landslide
susceptibility models were carried out by logistic regression and discriminant analysis of the significant conditioning factors
related to the characteristics of the slope and the upslope contributing area captured from the digital elevation model and
landslide distribution. The explanatory variables were tested (KS test, principal components and one-way and T-test) to select the most statistically significant ones before being introduced into the logistic and discriminant analyses.
Accuracy statistics and the receiver operating characteristic curve used for diagnosis and validation showed similar prediction
skills and a good fit to the data with more than 85% of unfailed cells properly classified for the two models. The evaluation
of the study area and the correlation function (R
2 = 0.83) between the models revealed that the discriminant model overestimated the susceptibility of the most stable zones
with respect to the logistic model. Different methods of producing susceptibility maps showed marked differences in matching
the models. Substantial spatial agreement (Kappa = 0.741) between binary maps produced by the standard cut-off value descended
moderately (Kappa = 0.540) as a result of superimposing maps with five susceptibility levels defined by landslide percentage.
Despite the fact that the two statistical models are similar in assessing susceptibility in the study area, the implications
for hazard and risk management can be different because of the conservative nature of the discriminant model. 相似文献
3.
Geologists may want to classify compositional data and express the classification as a map. Regionalized classification is a tool that can be used for this purpose, but it incorporates discriminant analysis, which requires the computation and inversion of a covariance matrix. Covariance matrices of compositional data always will be singular (noninvertible) because of the unit-sum constraint. Fortunately, discriminant analyses can be calculated using a pseudo-inverse of the singular covariance matrix; this is done automatically by some statistical packages such as SAS. Granulometric data from the Darss Sill region of the Baltic Sea is used to explore how the pseudo-inversion procedure influences discriminant analysis results, comparing the algorithm used by SAS to the more conventional Moore–Penrose algorithm. Logratio transforms have been recommended to overcome problems associated with analysis of compositional data, including singularity. A regionalized classification of the Darss Sill data after logratio transformation is different only slightly from one based on raw granulometric data, suggesting that closure problems do not influence severely regionalized classification of compositional data. 相似文献
4.
Richard A. Reyment 《Mathematical Geosciences》2010,42(4):447-452
Oyster encrustations on shells of the Albian (Cretaceous) ammonite species Knemiceras persicum (Iran) and K. syriacum (Lebanon) are analysed by discrete discriminant analysis, a method based on distributional difference in qualitative characters
appropriate for greatly unequal sample sizes. The two localities, which are approximately coeval and separated by a distance
of 2000 km, are shown to have different taphonometrical backgrounds, as manifested in the mode of occurrence and preservation
of the encrustations. 相似文献
5.
为高效地进行砂土液化的预测,运用逐步判别法,从8个液化影响因子中选择平均粒径、烈度、震中距等3个判别能力显著的影响因子,建立判别函数,并利用工程实例进行验证。研究结果表明：逐步判别分析模型预测性能良好,且能有效地选择对砂土液化起主导作用的因子。相比距离判别分析,逐步判别分析建立的判别函数更加稳定,且所需测试因子较少,节省了因试验和现场调查所耗费的大量人力、物力和时间,因此逐步判别分析是一种值得推广的砂土液化预测方法。 相似文献
6.
Influence of sample and terrain unit on landslide susceptibility assessment at La Pobla de Lillet,Eastern Pyrenees,Spain 总被引：2，自引：2，他引：0
The reliability of susceptibility maps depends largely on the quality of the information used for its evaluation. This study
seeks to analyze the influence of sample size and type on the results of discriminant analysis applied to shallow landslide
susceptibility assessment. The study also assesses the role of the terrain unit in discriminant analysis. To this end, two
databases based on fieldwork (slope unit) and GIS with 15- and 45-m grid cells (grid cell-based unit), were compared in the
same zone at La Pobla de Lillet, Spanish Eastern Pyrenees. The results show that although there is no significant influence
of the type of sample, it is necessary to use at least half of the individuals of the sample in order to obtain good results
from discriminant analysis. It is the terrain unit that exerts the biggest influence on the result of susceptibility. Some
morphometric parameters related to landslides were compared in the databases. The slope unit of the fieldwork database better
reflects the land characteristics than the regular grid used by GIS. The values of the variables obtained by GIS procedures
are smooth, obtaining mean errors for the slope angle variable of 19.5 and 33.5% for the grids of 15 and 45 m, respectively,
in the study area. One-way and T tests demonstrate that the smoothness of the values exerts a decisive influence on the discriminant results. Kappa’s analysis
shows that there is no significant equivalence between some of the categorical variables used in both databases. The use of
these variables demand the application of clearly defined criteria. The cell size should match the dimensions of the phenomenon
analyzed given the unsuitability of the grid of 45 m in this study. 相似文献
7.
Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopy – discriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopy – discriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia. 相似文献
8.
Experiments are described in which the threshold conditions for sediment entrainment are measured for uniform and mixed sand beds beneath both steady and combined steady/oscillatory flows. Derived critical shear stresses are compared with the mixed bed entrainment model of Wiberg & Smith (1987). As predicted by the model, coarser grains within a sand mixture are entrained at lower bed shear stresses than progressively finer grains. Entrainment occurs generally at lower shear stresses than predicted by the model, especially under unidirectional flows. This may be the result of grains resting in unusually unstable positions during the experiments because the beds are ‘unworked’ at the start of the experiments. The model of Wiberg and Smith predicts threshold conditions more accurately for the mixed beds if the bed pivoting angle is correctly defined. The pivoting angles of the beds used here are measured using a new technique designed specifically for comparison with the threshold data. The measured angles repeat the finding that the coarse grains are more mobile than the finer fractions of a mixture. The results are poorly described by the pivoting angle model presented by Wiberg & Smith (1987) and are better represented by a model of the form Φ = αDγ(Di/D50)β (after 21 ), where α, γ and β are empirical constants. The threshold model is found to be more effective using the improved pivoting relationship. The entrainment of grains is found to be easier beneath unidirectional flows than combined flows, in accordance with previous authors’ findings. A suggestion that this result is caused by a change in the erosion mechanism beneath wave flows is made. Wave boundary layers may act as an extended laminar sublayer over bed grains and reduce the erosive efficiency of the overlying current flow. The results of the experiment have implications for the natural sorting mechanisms of sediment beds being deposited in near-threshold flows. 相似文献
9.
The HMX (harmonic mixing) mixing calculation program, originally developed to solve geological problems, provides a solution fora posteriori multicomponent mixing problems, i.e., for computations of the proportions of components contributing to a mixture in such cases where the compositions of components and mixture are known. Naturally, these problematics are not restricted to geosciences, but occur throughout all disciplines of natural sciences. The method applied is a harmonic least-squares regression analysis in combination with an optimization technique known as the variable metric method. This procedure guarantees a least-squares regression solution for those real mixing problems, where all data treated are subject to error. In these cases, the application of graphical or least-squares methods for linear regression, as they were used previously, will give significantly different, probably distorted, results. 相似文献
10.
影响砂土液化的因素有很多,建立多指标的液化预测模型非常有必要。目前所有的多指标砂土液化预测模型,均默认选取的判别因子之间相互独立,不存在相关性,可能导致各判别因子之间存在信息叠加而发生误判。以唐山地震砂土液化的25个案例为样本,选取8个影响因素作为砂土液化预测的初始判别指标,首先采用主成分分析（PCA）对各判别指标进行分析,对存在相关性比较高的指标进行了降维处理。基于降维后的4个主成分换算得到新的样本数据,以18个案例为学习样本,建立主成分分析与距离判别分析（DDA）相结合的砂土液化预测模型。利用建立的预测模型对18个案例进行回判,结果全部正确。对其他7个案例的液化情况进行了预测,并与规范法、Seed方法、BP法、DDA法的判别结果进行分析比较,结果表明基于主成分分析与距离判别方法的砂土液化判别模型预测准确率为100%。将模型应用于工程实例,判别结果也与实际情况一致,表明该模型具有良好的预测功能,可在实际工程中应用。 相似文献
11.
The nature of the information - and its usefulness - that can be obtained from some of the more common multivariate statistical techniques is illustrated by their application to H and B horizon soils analyzed for 16 variables from the vicinity of the Key Anacon massive sulphide deposit (New Brunswick, Canada) where the geochemical response is erratic and the contrasts low. The theoretical bases of the statistical techniques are given in an appendix.Stepwise linear discriminant functions are employed as a classifying technique on H horizon soils to identify a regional anomaly, and on B horizon soils to derive discriminant scores to define the location of the sulphide zone. R-mode nonlinear mapping (RNLM) indicates that the variables Hg, Cl−, and conductance are closely correlated with the organic carbon content; variations in the latter are clearly related to variations in the secondary environment.Q-mode NLM using Pb, Zn, Co, and Ni as variables (identified as good discriminators by stepwise linear discriminant function) identify “outlying” anomalous samples related to the mineralized zones. A principal component biplot (using the same variables employed in the Q-mode NLM) indicates essentially the same samples as being anomalous as the Q-mode NLM. The biplot technique has the added advantage of also indicating which variable(s) is responsible for any particular sample being identified as anomalous.The practical result of the investigation is that the zone of sulphide mineralization defined by drilling and from underground data is confidently identified and defined. A number of geophysical magnetic anomalies over the same stratigraphic horizon has a relatively weak or no geochemical response, although a few locations are defined as second priority targets for follow-up work. 相似文献
12.
We present five new discriminant function diagrams based on an extensive database representative of basic and ultrabasic rocks
from four tectonic settings of island arc, continental rift, ocean-island, and mid-ocean ridge. These diagrams were obtained
after loge-transformation of concentration ratios of major-elements — a technique recommended for a correct statistical treatment of
compositional data. Higher % success rates (overall values from ∼ 83 to 97%) were obtained for proposing these new diagrams
as compared to those (∼82 to 94%) obtained from the discriminant analysis of the raw major-element concentration data (i.e.,
without the loge-transformation and without taking ratios of the compositional data, but using exactly the same database to provide an unbiased
comparison), suggesting that such a data transformation constitutes a statistically correct and recommended technique. The
new diagrams also resulted in less mis-classification of basic and ultrabasic rocks from known tectonic settings than the
diagrams obtained from the raw data. The use of these highly successful new discriminant function diagrams is illustrated
using Miocene to Recent basic and ultrabasic rocks from three areas of Mexico with complex or controversial tectonic settings
(Mexican Volcanic Belt, Los Tuxtlas volcanic field, and Eastern Alkaline Province), as well as older rocks from three areas
(Deccan, Malani, and Bastar) of India. Additionally, the major-element data from two ‘known’ continental arc settings are
used to show that they are similar to those from the island arc setting. Continental rift setting is inferred for all Mexican
cases and for one cratonic area of India (Malani) and an IAB setting for the Bastar craton. The Deccan flood basalt province
of India is used to warn against an indiscriminate use of those discrimination diagrams that do not explicitly include the
likely setting of the area under evaluation. An Excel template is also provided for an easy application of these new diagrams
for discriminating the four settings considered in this work. 相似文献
13.
Alfredo E. Prelat 《Mathematical Geology》1977,9(4):343-367
The statistical technique of discriminant analysis is used to define target areas for detailed general exploration given only general geological information and aeromagnetic anomaly blues. In the test area, located in Central Norway, on-going exploration surveys have revealed the presence of mineralization; however, it still has not been determined if any of the sites will beeconomically feasible. The area was divided into 1400 1-km × 1-km cells by superimposing square grid on 1:50,000-scale geological and geophysical maps. Later the area was divided into two subareas based on major differences in each area's geology. A number of geological natures and the aeromagnetic anomaly values were coded systematically in each cell. The cells representing an advanced degree of exploration were chosen as control cells in each of the subareas. The geological and geophysical parameters were transformed, by means of relatively simple transformations, to produce near-normal frequency distributions. A discriminant function was then obtained by discriminant analysis to divide the control data into two groups, cells with presence of mineral occurrence and cells without mineral occurrence. the discriminant function obtained for the control area proved to be relevant both geologically and statistically. Consequently, the discriminant equation was applied to cells outside the control area. The cells were assigned to one of the two groups by entering the geologic factors pleasured from the maps into the discriminant model. The exploration potential of a large number of cells was evaluated by this procedure. To test the results, field work including geochemical sampling was carried out in the cells with highest probability of mineral occurrance The field work results have shown that the application of discriminant analysis to geological information at 1:50,000 scale with 1-km × 1-km cells combined with a careful selection of techniques for transforming the variables is a feasible method for predicting gaeralization, and as such could become a valuable tool for mining exploration.This paper was presented at Symposium 116.3, Quantitative Strategy for Exploration, held as part of the 25th International Geological Congress, Sydney, Australia, August 1976. 相似文献
14.
Olusegun Areola 《Geoforum》1974,5(4)
In Montgomeryshire, Wales, UK, a study was carried out to test the validity of a soil mapping technique based on the photo-interpretation of land facets. Land facets were used as the means for extrapolating, using aerial photographs, soil properties between widely separated parts of the county. Statistical techniques such as coefficient of variation, analysis of variance and discriminant analysis, were used in testing the validity of land unit classifications of the terrain and of the predictions of soil-land attributes from aerial photographs.The results show that the land facets are uniform soil areas with a considerable degree of homogeneity in those soil properties which are genetically and morphologically important, such as particle size distribution, colour, stòne content, pH and free iron oxide. The facets are, however, highly variable notably in the distribution of exchangeable cations and organic carbon. The similarity between analogous facets based on individual soil parameters is not very great and there are significant differences within groups related to ground drainage and parent material lithology. When all parameters are considered simultaneously, however, the similarity between them is proven. 相似文献
15.
An iterative method of adaptive pattern recognition is used to allocate unclassified individuals to an a priori classification. The model is similar in form to a linear discriminant function, but the coefficient vector is determined by iteration. The method can be used with binary data, and with variables whose statistical distributions are not normal; it is therefore a useful technique for geologists. 相似文献
16.
基于场变量的边坡稳定分析有限元强度折减法? 总被引：1，自引：0，他引：1
有限元强度折减法在实施过程中往往要根据不同的折减系数手工修改输入文件,并不断进行试算,过程较繁琐。为了简化计算过程,提高计算效率,在有限元强度折减法的基础上,结合ABAQUS提供的场变量,提出一种适用于有限元强度折减计算的新方法--基于场变量的有限元强度折减法。通过在ABAQUS中设置岩土体黏聚力与内摩擦角为场变量的函数,场变量为增量步时间t的函数,从而通过控制增量步时间t实现黏聚力与内摩擦角的折减,通过一次计算即可求得边坡的安全系数,无需手工修改折减系数反复试算。结合有关文献对该方法用于边坡稳定分析的可行性进行了验证,并与二分法确定安全系数的计算效率进行了比较。结果表明：该方法求得的安全系数是有效可靠的,用于边坡稳定性的计算是可行的,简化了有限元强度折减法的计算过程,提高了计算效率。 相似文献
17.
Olusegun Areola 《Geoforum》1974,5(4):25-38
In Montgomeryshire, Wales, UK, a study was carried out to test the validity of a soil mapping technique based on the photo-interpretation of land facets. Land facets were used as the means for extrapolating, using aerial photographs, soil properties between widely separated parts of the county. Statistical techniques such as coefficient of variation, analysis of variance and discriminant analysis, were used in testing the validity of land unit classifications of the terrain and of the predictions of soil-land attributes from aerial photographs.The results show that the land facets are uniform soil areas with a considerable degree of homogeneity in those soil properties which are genetically and morphologically important, such as particle size distribution, colour, stòne content, pH and free iron oxide. The facets are, however, highly variable notably in the distribution of exchangeable cations and organic carbon. The similarity between analogous facets based on individual soil parameters is not very great and there are significant differences within groups related to ground drainage and parent material lithology. When all parameters are considered simultaneously, however, the similarity between them is proven. 相似文献
18.
Basanta K. Sahu 《Mathematical Geology》1982,14(6):577-587
Optimal discrimination among several groups can be achieved by simultaneous diagonalization of pooled within-group, W, and among-group, A, sums of squares and cross-product matrices formed by utilizing axial-ratio sample statistics of quartz grains belonging to different sieve grades. This method maximizes the ratio of among-group cross products to within-group cross product quadratic forms (V'AV/V'WV)and simultaneously yields discriminant scores whose correlation coefficients are zero for group means as well as for within each group. This procedure enables a simple Euclidean distance measure for partitioning the discriminant space for assignment. Although W–1
and Amatrices are symmetric, the W–1 Amatrix needed for multigroup discrimination is asymmetric and hence the eigenstructure of W–1 Ais obtained by simultaneous diagonalization of Wand Amatrices. The first four sample statistics (mean, standard deviation, skewness, kurtosis) of normalized axial-ratios are required for discrimination, although the mean and standard deviation are the most important discriminators. 相似文献
19.
Sampling design optimization for spatial functions 总被引：4，自引：0，他引：4
Ricardo A. Olea 《Mathematical Geology》1984,16(4):369-392
A new procedure is presented for minimizing the sampling requirements necessary to estimate a mappable spatial function at a specified level of accuracy. The technique is based on universal kriging, an estimation method within the theory of regionalized variables. Neither actual implementation of the sampling nor universal kriging estimations are necessary to make an optimal design. The average standard errorand maximum standard error of estimationover the sampling domain are used as global indices of sampling efficiency. The procedure optimally selects those parameters controlling the magnitude of the indices, including the density and spatial pattern of the sample elements and the number of nearest sample elements used in the estimation. As an illustration, the network of observation wells used to monitor the water table in the Equus Beds of Kansas is analyzed and an improved sampling pattern suggested. This example demonstrates the practical utility of the procedure, which can be applied equally well to other spatial sampling problems, as the procedure is not limited by the nature of the spatial function. 相似文献
20.
针对砂土地震液化预测问题,基于Fisher判别分析原理(FDA),选用平均粒径、不均匀系数、标贯击数、地下水水位、砂层埋深、剪应力与有效上覆应力比、地震烈度.震中距等8个实测指标为判别因子,建立Fisher线性判别函数模型,对砂土液化进行预测.研究结果表明,Fisher判别分析结果与神经网络输出结果一致,优于规范法和Seed法判别结果,验证了该模型的合理性和可靠性.运用该模型进行判别分析,简易方便,分类效率高,对砂土液化判别快速、有效,模型适用性强,具有一定的工程应用前景. 相似文献