Stochastic Simulation of Patterns Using Distance-Based Pattern Modeling

The advent of multiple-point geostatistics (MPS) gave rise to the integration of complex subsurface geological structures and features into the model by the concept of training images. Initial algorithms generate geologically realistic realizations by using these training images to obtain conditional probabilities needed in a stochastic simulation framework. More recent pattern-based geostatistical algorithms attempt to improve the accuracy of the training image pattern reproduction. In these approaches, the training image is used to construct a pattern database. Consequently, sequential simulation will be carried out by selecting a pattern from the database and pasting it onto the simulation grid. One of the shortcomings of the present algorithms is the lack of a unifying framework for classifying and modeling the patterns from the training image. In this paper, an entirely different approach will be taken toward geostatistical modeling. A novel, principled and unified technique for pattern analysis and generation that ensures computational efficiency and enables a straightforward incorporation of domain knowledge will be presented.     

Quantifying Three-Dimensional Silicate Fabrics in Cumulates Using Cumulative Distribution Functions

We present a new method for quantifying three-dimensional silicatefabrics and the associated uncertainties from grain orientationdata on three orthogonal sections. Our technique is appliedto the orientation of crystallographic features and, hence,yields a fabric related to the lattice-preferred orientation,although the method could be applied to shape-preferred orientationsor strain analysis based on passive linear markers. The orientationdata for each section are represented by their cumulative distributionfunction, and an iterative procedure is used to find the symmetricsecond-rank strain tensor that will simultaneously satisfy thecumulative distribution functions observed on each section.For samples with well-developed fabrics, this technique providesa much closer match to the sectional data than do previous techniquesbased on eigenparameter analysis of two-dimensional orientationdata. Robust uncertainty estimates are derived from a non-parametricbootstrap resampling scheme. The method is applied to two cumulates:one with a well-developed fabric and the other with a weak fabric,from the Stillwater complex, Montana. The silicate petrofabricorientations obtained for these samples compare favorably withindependent direct estimates of the volume fabric from electronbackscatter diffraction and magnetic techniques. KEY WORDS: cumulates; fabrics; quantitative; Stillwater complex; textural analysis     

Filter-Based Classification of Training Image Patterns for Spatial Simulation

Multiple-point simulation, as opposed to simulation one point at a time, operates at the pattern level using a priori structural information. To reduce the dimensionality of the space of patterns we propose a multi-point filtersim algorithm that classifies structural patterns using selected filter statistics. The pattern filter statistics are specific linear combinations of pattern pixel values that represent directional mean, gradient, and curvature properties. Simulation proceeds by sampling from pattern classes selected by conditioning data.     

Multifractality as a Measure of Spatial Distribution of Geochemical Patterns

To quantify the spatial distribution of geochemical elements, the multifractality indices for Zn, Cu, Pt, Pd, Cr, Ni, Co, Pb, and As in lake-sediment samples in the Shining Tree area in the Abitibi area of Ontario are determined. The characterization of multifractal distribution patterns is based on the box-counting moment method and involves three functions: a mass exponent function (q); Coarse Hölder Exponent (q); and fractal dimension spectrum f( (q)). Properties of these functions at different values of q, characterize the spatial distribution of the variable under study. It is shown that the degree of multifractality defined by (1) can be used as a measure of irregularity of geochemical spatial dispersion patterns. The variations of Zn and Cu in the study area are characterized by relatively low degree of multifractality, whereas those for Pt, Pd, Cr, Ni, and Co; and particularly for As and Pb are characterized by higher multifractality indices.In the case of Zn and Cu, singularity spectra are close to a monofractal compared to the ones for As an Pb. The determination of multifractality indices allows us, in a quantitative way, to study the pattern of metal dispersions and link them to different physical processes, such as metal adsorption by organic material or glaciogenic processes.     

On the Optimal Estimation of the Cumulative Distribution Function in Presence of Spatial Dependence

For spatial analysis of data, the optimal prediction of the cumulative distribution function (c.d.f.) is made difficult by the presence of spatial dependence, particularly when data are clustered. Several methods have been proposed in the literature to correct for the redundancy which is present when the observed values are correlated. Most of them are based on an unequal weighting of the values for the computation of the c.d.f. The methodology is extended by defining weights which depend both on the spatial correlation and on the threshold value. If a parametric multivariate distribution is assumed, optimal weights can be obtained conditionally to the choice of this distribution, and a nonparametric indicator estimate of the c.d.f. can be defined a posteriori. The method can be extended in order to provide kernel smoothed estimates of the c.d.f., by replacing the indicator functions by other functions taken here as complementary differentiable c.d.f., whose parameters are defined in order to preserve the unbiasedness and minimum variance property of the estimate, conditionally to the choice of the a priori distribution. A simulation study is conducted in order to emphasize the properties of the various methods. It is found that, even for bounded and positively skewed distributions, a simplified version of the method seems to perform quite well without significant loss of efficiency, and provides smooth estimates of the c.d.f. which can be differentiated in order to obtain density estimates. These estimates do not depend highly on the choice of the parameters for the a priori distribution, and yet they respect major characteristics of the a priori c.d.f., such as lower and upper bounds, which are mainly dictated by the nature of the variable under study. A practical case study is conducted on cobalt concentrations for various rock types in the Swiss Jura, illustrating the applicability of the methodology for real datasets.     

现代冲积河流的河型空间转化模式探讨

论述了现代冲积河流系统中常见河型的自然分布及转化特征,归纳了河型从上游向下游发生空间转化的 5种主要模式。这些河型转化模式发生的相对频率是不同的,其中从辫状河流向曲流河流转化的发生频率最大。文中通过具体实例总结了这些转化模式分别发生时的主要影响因素。     

Patterns of Spatial Methane Distribution in the Upper Layers of the Permafrost in Central Yakutia

This article presents the results of long-term field studies on methane in the upper part of the permafrost for different geomorphological levels of Central Yakutia. Patterns of the spatial distribution of the methane content across different landscapes were found. The difference in the methane content in sediments of the Late Pleistocene ice complex on the left and right banks of the Lena River was found for the inter-alas areas. This was caused by different conditions of formation: the formation of a thin cover of deposits occurred under sub-aqua conditions favorable for methanogenesis on the left bank and in more dry aerobic conditions on the right bank. The highest concentrations of methane were found in alas deposits, where the major role belongs to the duration of freezing after draining the thermokarst lake in subaerial conditions. The methane content is highly variable both laterally and with depth in the studied deposits, but there is no redistribution after freezing; this allows one to use methane as a paleo indicator of the conditions of accumulation and freezing of sediments.     

Spatial Distribution and Long-term Movement Patterns of Cownose Rays Rhinoptera bonasus Within an Estuarine River

Passive acoustic telemetry was used to monitor the movements of cownose rays (Rhinoptera bonasus) within the Caloosahatchee River estuary in Southwest Florida. Twelve rays were tracked within the river between January 2004 and May 2005 for periods up to 234 days. Linear home range was calculated for all individuals and ranged between 0 and 18.4 km (daily) and 1 and 22.3 km (overall). Ray position within the river was compared to changing water quality parameters throughout the study. Although home range size did not increase with increasing salinity, individuals did occur farther upriver with decreasing flow rates and increasing salinity. There were no differences detected between day and night distribution patterns. Movement and presence patterns demonstrated significant use of the estuarine river over all months, indicating that cownose rays in southwest Florida may not undertake long seasonal migrations as established for other parts of their range.     

Stochastic Simulation Model for the Spatial Characterization of Lung Cancer Mortality Risk and Study of Environmental Factors

This paper presents a study in which the lung cancer risk in males was characterized based on a simulation model of mortality rates. Block sequential simulation of mortality rates, measured in counties of different sizes, was implemented and applied to a normal grid of continental Portugal with high spatial resolution. The uncertainty in the mortality rate measurements, directly related to differences in the population size of each county, was integrated in a block direct sequential simulation through Poisson kriging of local means and variances. Three age groups were examined: 50–59, 60–69, and 70–79 years. After the continuous geographic patterns of lung cancer risk were obtained, factors potentially associated with the main areas of risk were analyzed for southern Portugal. Thus, a defined class of land use and dry weather events, related to airborne particulate matter, were found to be associated with high-risk areas, resulting in high local spatial correlation patterns in all three age groups.     

Distribution Functions of Tsunami Wave Heights

The problem of describing the distribution functions of tsunami wave heights is discussed. Data on runup heights obtained in field surveys of several tsunamis for the last decade are used to calculate the empirical distribution functions. It is shown that the log-normal distribution describes the observed data well. This means that the irregular topography and coastline are major factors which influence the height distribution. The power distribution related with the geometric decay of the propagated wave is a good approximation for one event (Sulawesi, January 1, 1996) only. Results of a numerical simulation of the tsunami event in the Japan (East) Sea on July 12, 1993 are presented. It is shown that the computed wave height distribution, obtained by using the runup correction in the framework of nonlinear shallow-water theory, is in good agreement with the observed height distribution. Simulations are used to study the transformation of the distribution function on different distances from the source.     

Comparison on Spatial Distribution of Hydrogen and Oxygen Stable Isotope GCM Simulation in Global Precipitation

The general circulation models are used to simulate hydrogen and oxygen stable isotope in precipitation, which can enhance our understanding of the migratory processes of water stable isotope in water cycle and remedy disadvantages of measured data in spatial and temporal discontinuity. We used ten GCM (General Circulation Models) simulated data including stable isotope water cycle, and analyzed the spatial distribution characteristics of oxygen stable isotope effect in global precipitation. Meanwhile, we compared different simulated results as well as simulated results and the GNIP (Global Network of Isotopes in Precipitation) actual monitoring results. Our main purposes were to evaluate the simulative validity of stable isotope atmospheric circulation and improve our understanding and cognition for stable isotopic effect in water cycle. The results indicated that isoGSM, ECHAM4, LMDZ4 and HadAM3 showed good performances in simulating δ¹⁸O. Expect HadAM3, other simulated conclusion of models had good performances in the aspect of simulate seasonal difference of δ¹⁸O in spatial distribution. The simulated results of isoGSM, GISS E-F, ECHAM4, GISS E-N and LMDZ4 matched monitoring results more in the aspect of simulating relationship between δ¹⁸O and air temperature in spatial distribution. LMDZ4, isoGSM, GISS E-F, ECHAM4 and MUGCM had stronger capacity in the aspect of simulating relationship between δ¹⁸O and precipitation in spatial distribution. GISS E-F, isoGSM and GISS E-N had more advantage of simulate global meteoric water line.     

Multifractal Simulation of GeochemicalMap Patterns

INTRODUCTIONThe mathematical modeling of geochemical data continuesto present an important challenge to earth scientists. Basically,the available data are 2-dimensional realizations of 3dimensional patterns, which are the results of one or more genetic processes that usually are poorly understood. It may bedifficult to project from the observations into the rock mass. Inthis paper, multifractal modeling is advocated as a methodologyto characterize geochemical patterns. If a geochemical pa…     

日以下尺度降雨随机模拟研究进展

目前我国作物生长、土壤侵蚀等应用模式发展很快,利用这些模式进行气候变化影响评价的研究逐渐成为热点,但日以下尺度降雨观测资料却严重不足,迫切需要针对我国复杂的气候条件建立日以下尺度降雨模拟模型,为应用模式提供更为精细的降雨资料输入。重点从次降雨事件的划分方法、次降雨事件模型的模拟过程、Bartlett-Lewis和Neyman-Scott点过程模型的模拟过程、参数估计、参数敏感性分析以及模型改进等方面综合概述了日以下尺度降雨随机模拟的进展,同时给出这几种模型的对比研究结果,从而为人们根据不同目的和条件选择不同模型提供借鉴。最后指出,结合点过程和次降雨事件等方法优点的混合模型——基于天气分型的随机模拟模型以及将统计与动力方法相结合的模拟模型,可能是未来降雨模拟的重要发展方向。     

白令海与西北冰洋表层沉积物中四醚膜类脂物研究及其生态和环境指示意义

通过对中国第3次和第4次北极考察在白令海和西北冰洋采集的65个表层样沉积物中生物标记物四醚膜类脂物(GDGTs)的研究,发现西北冰洋表层沉积物中类异戊二烯和支链GDGTs的浓度分布大致以楚科奇海和波弗特海的陆坡为界线,呈现南高北低的特征,这一特征主要与水体生产力和陆源有机质的输入量有关.基于GDGTs的陆源输入指数BIT显示,从楚科奇海北部到高纬度区的阿尔法脊,陆源有机质的相对比例明显增加,与有机碳稳定同位素等结果一致,表明BIT可以用来指示北极陆源有机质输入量的变化.应用前人TEXL86-SST方程估算的研究区表面海水温度SST与现代年均SST和夏季平均SST的相关性较差,原因可能与陆源输入的类异戊二烯GDGTs干扰以及低的古菌生产力有关.从季节性海冰覆盖区到永久性海冰覆盖区,基于支链GDGTs的环化指数CBT明显升高,可能反映了CBT对海冰覆盖状况的响应,但其响应机制还不清楚.基于支链GDGTs的环化指数CBT和甲基化指数MBT估算的北极陆地年均大气温度和土壤pH差异较大,可能是由表层沉积物的来源复杂以及混合作用造成的.     

中国不同类型天然气的分布特点

<正> 截止1998年底,中国陆上及近海海域气田总数为321个,其中小型252个,中型54个,大型15个。大中型气田构成已探明地质储量的主体,占84%。在层位上,已发现气田主要分布在新生界、上古生界和下古生界。在中国已发现的大中型气田中,天然气的分布特点表现在以下六个方面:1 多种类型天然气混合分布在同一气藏中由于中国多数盆地具有多旋回的演化历史,在纵向上盆地存在多个含气系统,使不同类型的天然气存在于同一地层中的现象十分普遍。魏永佩特别强调,在同一气藏中存在天然气的混源现象。在中国已发现的大中型气田中,不同研究者对气田的成因类型归属总是有一定分歧,很难将气田划分为某种典型的成因类型。实际上,在中国已发现的大中型气田中,以某种     

Relationships between Nutrient Enrichment and Benthic Function: Local Effects and Spatial Patterns

Eutrophication-induced changes to benthic faunal activities are problems of significant ecological impact, affecting global nutrient budgets as well as local trophic connections. We address the question of how nitrogen loads to estuarine embayments alter the bioturbation activities of benthic fauna. Specifically, we related local benthic activities to calculated local nitrogen concentrations for 22 northeastern US estuaries. These local nitrogen concentrations were derived from the calculated nitrogen loading for the embayment together with the spatial distribution of the local flushing time. Our results showed a maximum bioturbation rate at intermediate nitrogen concentrations or a “hump-shaped” pattern of response. This behavior was evident in all embayments that had a range of concentrations including low, intermediate, and high values. Embayments where sampling did not include this full range did not show this behavior. This work provides methods and guidance to help managers make decisions concerning the effects of nitrogen loading on the activities and well-being of benthic fauna in coastal embayments. The novelty of this approach lies in identifying the response of bioturbation to nitrogen loading in many systems, without costly and time-consuming speciation of benthic fauna, and also in rapidly identifying embayments and aquatic areas with vulnerable fauna. These results are ecologically significant in supporting the hypothesis that benthic organism abundance and activity will peak at mid-levels of nitrogen due to the interplay of food availability and oxygen levels, noting that the critical levels of these factors differ among water bodies.     

Progressive Failure of Slopes: Stochastic Simulation Based on Transition Probabilities and Markov Chains

Geotechnical and Geological Engineering - A reliability analysis framework for the stochastic simulation of slope progressive failure is proposed in the current work. Progressive failure is...     

成矿环境空间结构的模糊建模

为了提高矿产预测的精度和可靠性, 必须分析和利用与矿床有关的空间结构信息.提出了一种用模糊集建立成矿环境空间结构模型的方法.成矿环境空间结构是地质变量在矿床周围的分布, 可用变量与空间点之间的模糊关系来描述.同一地区的同类矿床, 其空间结构具有一定相似性, 通过这种相似性的极大化可对结构模型进行优化.优化的结构模型是一种包含了方向和距离关系的特殊的空间关联规则集, 也是模糊推理矿产预测的推理规则库.通过模糊推理进行结构相似性的比较, 可对任意点上的找矿有利性进行预测.以云南东川地区铜矿预测的实例说明了该方法具有良好的应用效果.      

High-Order Data-Driven Spatial Simulation of Categorical Variables

Mathematical Geosciences - Modern approaches for the spatial simulation of categorical variables are largely based on multi-point statistical methods, where a training image is used to derive...