Estimation of statistical parameters for censored lognormal hydraulic conductivity measurements

Field tests of hydraulic conductivity (e.g., injection test, pumping test, etc.) in low permeability formations are subject to censoring due to the detection limit of the instruments used. An iterative method of estimating the mean and variance of hydraulic conductivity data with a presumed log-normal distribution function is presented. This method accounts for the data that are actually below the lower detection limit (called truncated data) and thus gives distribution parameters that are more representative for the underlying distribution. The proposed method is then tested on two simulated normally distributed random datasets having different variances. The results show that the means and variances estimated by the proposed method are very accurate. Finally, the method is used to estimate the mean and variance of hydraulic conductivity data from single hole water injection tests in a fractured geological formation.     

Analysis and mapping of geochemical anomalies using logratio-transformed stream sediment data with censored values

There is lack of research and documentation of actual (as opposed to theoretical) benefits (e.g., mineral deposit discovery) of developments in compositional data analysis and imputation of censored values to mineral exploration geochemistry. In the present study, analyses of logratio- and ln-transformed stream sediment geochemical data containing ca. 30% of samples with censored values of a pathfinder element for the mineral deposit-type of interest yielded the following findings. Exclusion of those samples supports interpretation of multi-element anomalies reflecting the presence of mineralization. However, the multi-element anomaly maps obtained by exclusion of those samples are barely better than the multi-element anomaly maps derived by inclusion of those samples after replacing the censored values with 1/2 of detection limit or with imputed values. Logratio (i.e., alr, clr, or ilr) transformation, compared to ln-transformation, of stream sediment geochemical data does not improve mapping of pathfinder element anomalies reflecting the presence of mineralization. However, stream sediment geochemical data, excluding or including censored values (replaced with 1/2 of detection limit or with imputed values), should be clr- or ilr-transformed to enhance recognition of anomalous multi-element associations reflecting the presence of mineralization. The anomaly maps of multi-element associations derived from ilr-transformed data are better, albeit slightly, than the anomaly maps of multi-element associations derived from clr-transformed data. In the present study, the main benefit of either clr- or ilr-transformation, compared to either ln- or alr-transformation, of stream sediment geochemical data is the enhancement of anomalous multi-element associations reflecting the presence of mineralization. This is an important benefit because variations in trace element concentrations in regional-scale stream sediment geochemical data are mostly due to lithology and other factors (or processes) unrelated to mineralization. Further investigations of various exploration geochemical data are needed to demonstrate and document the actual (as opposed to theoretical) benefits of developments in compositional data analysis and imputation of censored values to mineral exploration.     

区域化探数据处理的几种分形方法

地球化学变量兼有随机性、确定性和区域结构性的特征,传统的数学方法难以精确地描述地球化学变量的空间分布规律,而新兴的分形几何是刻画空间不规则形体的一种比较有效的工具,且分维值可以表征空间不规则形体的确定性本质。基于分形原理,提出含量-总量法、空间分形插值法和分形趋势面法3种新的分形技术,应用于区域化探数据处理。在几个典型矿区应用后发现,上述分形方法不仅可以有效地模拟地球化学变量的空间分布特征,而且在保留原始有效异常信息的基础上可以更合理地区分地球化学变量的背景与异常,具有发现和强化弱异常信息的重要功效。     

A spatial analysis method for geochemical anomaly separation

One purpose of using statistical methods in exploration geochemistry is to assist exploration geologists in separating anomalies from background. This always involves two types of negatively associated errors of misclassification: type I errors occur when samples with background levels are rejected as background; and type II errors occur when samples with anomalous values are accepted as background. A new spatial statistical approach is proposed to minimize errors of total misclassification using a moving average technique with variable window radius. This method has been applied for geochemical anomaly enhancement and recognition as demonstrated by a case study of Au and Au-associated data for 698 stream sediment samples in the Iskut River area, northwestern British Columbia. Similar results were obtained using the fractal concentration-area method on the same data. By employing spatial information in the analysis, the process of selecting anomalies becomes less subjective than in more traditional approaches.     

如何利用Excel处理化探数据

利用Excel可以实现对化探数据多种项目的处理,如正态性检验;背景值及异常下限的确定;一元及多元回归分析;相关系数(R型聚类分析)以及一次趋势分析等,操作直观,目前在没有流行地质行业软件的情况下,不失为一种较为可取的选择。通过这种方法,可以较为简洁地实现对一定数量化探数据的处理,为地质找矿工作提供了化探方面的可靠依据。     

水环境质量综合评价的多目标决策-理想区间法

对水环境质量综合评价中应用的多目标决策-理想点法进行了分析,认为实际上水环境质量评价标准是区间概念而非点的概念,因而传统的多目标决策-理想点法把评价标准处理成理想点存在一定缺陷。为了克服这种缺陷,提出了一种多目标决策-理想区间法(MODMIIM)。介绍了MODMIIM的原理,给出了它的构成方法,并把它应用到水环境质量综合评价中。MODMIIM与PP模型和神经网络法相比,简单、有效;与多目标决策理想点法相比,具有更大的适用性。MODMIIM可广泛应用于各种环境质量综合评价中。     

国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

国际地球化学填图样品分析方法和数据对比

以中国和世界发达国家或地区(欧洲、北美、澳大利亚与日本)过去10年内完成的或目前正在开展的全球性或国家性地球化学填图项目为例,总结了国际地球化学样品分析技术的新进展,并以中国实验室与欧洲实验室的分析数据的对比结果,剖析国际地球化学填图样品分析技术面临的挑战。研究表明:分析组成地壳所有元素的构想已被越来越多国家性、全球性地球化学填图项目所采纳;中国是世界上唯一具有填图样品76元素分析能力的国家;高水平的分析实验室(欧洲与中国)取得的数据大部分可以实现对比,但仍有10余个元素的分析数据存在明显偏差。实现所有分析元素数据的全球可对比,应是今后国际地球化学填图样品分析技术的主要发展方向。     

Normal and lognormal data distribution in geochemistry: death of a myth. Consequences for the statistical treatment of geochemical and environmental data

All variables of several large data sets from regional geochemical and environmental surveys were tested for a normal or lognormal data distribution. As a general rule, almost all variables (up to more than 50 analysed chemical elements per data set) show neither a normal or a lognormal data distribution. Even when different transformation methods are used more than 70 % of all variables in every single data set do not approach a normal distribution. Distributions are usually skewed, have outliers and originate from more than one process. When dealing with regional geochemical or environmental data normal and/or lognormal distributions are an exception and not the rule. This observation has serious consequences for the further statistical treatment of geochemical and environmental data. The most widely used statistical methods are all based on the assumption that the studied data show a normal or lognormal distribution. Neglecting that geochemcial and environmental data show neither a normal or lognormal distribution will lead to biased or faulty results when such techniques are used. Received: 21 June 1999 · Accepted: 14 August 1999     

An efficient probabilistic back-analysis method for braced excavations using wall deflection data at multiple points

This paper presents an efficient Bayesian back-analysis procedure for braced excavations using wall deflection data at multiple points. Response surfaces obtained from finite element analyses are adopted to efficiently evaluate the wall responses. Deflection data for 49 wall sections from 11 case histories are collected to characterize the model error of the finite element method for evaluating the deflections at various points. A braced excavation project in Hang Zhou, China is chosen to illustrate the effectiveness of the proposed procedure. The results indicate that the soil parameters could be updated more significantly for the updating that uses the deflection data at multiple points than that only uses the maximum deflection data. The predicted deflections from the updated parameters agree fairly well with the field observations. The main significance of the proposed procedure is that it improves the updating efficiency of the soil parameters without adding monitoring effort compared with the traditional method that uses the maximum deflection data.     

基于GEOROC大数据分析地壳厚度地球化学指标

前人研究认为,火山岩中部分地球化学指标与岩浆弧地壳厚度之间存在一定的相关性,并通过统计主量元素K2O、Ca O和Na2O指标及微量元素Ce/Y、Sm/Yb、Dy/Yb、Sr/Y、La/Yb指标与地壳厚度之间关系,约束地质史上某些区域的地壳厚度发展和变化。本文基于GEOROC数据库,以Si O2含量57%和火山岩年龄23Ma为界,将全球火山岩数据分成年轻-壳源( 57%,23Ma)、年轻-幔源(57%,23Ma)、古老-壳源( 57%, 23Ma)和古老-幔源(57%, 23Ma)四个数据集,并通过核函数估计方法获得了各个地球化学指标与地壳厚度的归一化联合概率密度分布图。本文统计结果表明,年轻-幔源火山岩中的K2O含量分布与壳源火山岩呈现指数正相关关系、Ca O含量分布于地壳厚度呈现线性负相关关系,年轻-壳源火山岩中Ce/Y、La/Yb和Sm/Yb与现今地壳厚度有指数正相关关系。由以上5种地化指标建立的回归方程确定系数R2均大于0. 7,可以认为相关关系显著。本文认为幔源岩浆在穿透地壳到达地表过程中,地壳厚度控制了富K壳源物质进入地幔熔体和富Ca矿物结晶分异过程,导致了火山岩中K2O和Ca O含量的相关变化;而下地壳部分熔融形成的壳源岩浆,不同深度压力控制了残留相矿物比例,导致Ce/Y、La/Yb和Sm/Yb体现出与地壳厚度的相关性。本文建立的回归函数是基于大量数据概率密度分布的统计分析得出的,由于离群数据普遍存在,回溯历史地壳厚度变化需要大量数据统计支撑,否则难以获得可靠的结果。     

Variational method for objective analysis of scalar variable and its derivative

In this study real time data have been used to compare the standard and triangle method by performing the objective analysis of mean sea level pressure. In the standard method, derivative fields are obtained from the grid point data using finite difference scheme whereas in the triangle method, a set of non-overlapping triangles are formed from the observations and the scalar and the spatial derivatives are computed directly at the centroid of each of the non-overlapping triangles. These scalars and their derivatives are then mapped to uniform grids by using the standard method. It has been found that objectively analysed scalar field obtained using standard method is superior to the scalar field derived by the triangle method, whereas the derivative fields produced by triangle method are superior to the derivative fields produced using standard method. A variational objective analysis scheme has been developed and an experiment has been carried out with depression case of June (11–15) 2004. It is found that the new scheme (variational) is able to extract the better parts of both triangle and standard methods. The results of this study will be useful in carrying out diagnostic calculations that involve derivative estimates.     

多源异构地质数据集成方法应用研究

大数据技术的高速发展为地质数据挖掘与分析带来了新的机遇。借鉴大数据技术的思想,提出了一种多源异构的地质数据集成方法,为数据挖掘、地质数据信息化服务提供了技术基础。针对北京周口店研究区,建立了其野外地质三维综合信息平台,将各类地表、地质体、地质信息等结构、半结构、非结构数据集成到统一的平台系统中,实现了研究区域相关地质数据的集成管理、可视化浏览、查询与分析,为大数据方法在地质领域的应用提供了新的思路。     

微地震监测数据时频域去噪方法

原始微地震监测数据的信噪比相对较低,监测数据品质决定了微地震有效信号的定位精度,提高监测数据信噪比是微地震处理的关键环节。改进S变换对窗函数进行能量归一化处理,解决了常规S变换时频谱中频率定位不准的问题,具有更高的时频分辨率精度。利用改进S变换的良好二维时频域聚焦特性,设计时变的二维时频域滤波器,将时频域去噪方法引入到微地震监测数据的去噪处理中。利用改进S变换对微地震监测数据进行时频分析,能够更加准确地分析不同信号分量的振幅能量以及频率随时间的变化情况,实现微地震有效信号分量与噪声干扰分量的有效分离。通过合成模拟信号和实际井中微地震监测数据的试处理和对比分析,验证了该方法的可行性和有效性。     

Application of fractal content-gradient method for delineating geochemical anomalies associated with copper occurrences in the Yangla ore field,China

Fractal and multi-fractal content area method finds application in a wide variety of geological, geochemical and geophysical fields. In this study, the fractal content-gradient method was used on 1:10,000 scale to delineate geochemical anomalies associated with copper mineralization. Analysis of geochemical data from the Yangla super large Cu-Pb-Zn polymetallic ore district using the fractal content-gradient method, combined with other geological data from this area, indicates that ore-prospecting in the ore district should focus on Cu as the main metal and Pb-Zn and Au as the auxiliary metals. The types of deposits include (in chronological order) re-formed sedimentary exhalative (SEDEX), skarns, porphyries, and hydrothermal vein-type deposits. Three ore-prospecting targets are divided on a S–N basis: (1) the Qulong exploration area, in which the targets are porphyry-type Cu deposits; (2) the Zongya exploration area, where the targets are porphyry-type Cu and hydrothermal vein-type Cu-Pb polymetallic deposits; and (3) the Zarelongma exploration area, characterized mainly skarn-type “Yangla-style” massive sulfide Cu-Pb deposits. Our study demonstrates that the fractal content-gradient method is convenient, simple, rapid, and direct for delineating geochemical anomalies and for outlining potential exploration targets.     

利用地球化学资料评价水淹层方法研究:以大庆杏南油田为例

通过对水淹层地球化学资料的分析,总结出了不同程度水淹层的地球化学特征,提出了利用地球化学资料从定性识别到定量评价的水淹层评价思路,建立了水淹层水淹程度定性识别方法、剩余油饱和度和含水率定量评价模型.对储层物理性质、岩性、流体性质、水淹程度不同的108口井529层水淹层进行了评价,剩余油饱和度与经校正后的密闭取芯井岩芯分析剩余油饱和度非常接近,水淹级别、含水率与单层试油结果一致.证明利用地球化学资料评价水淹层方法是可行的,结果是可靠的,该方法有很好的推广应用前景.     

The loghyperbolic: An alternative to the lognormal for modeling oil field size distribution

The lognormal distribution is widely used to represent the distribution of deposit or reserve size of oil and gas fields. The purpose of this paper has been to investigate the potential usefulness of the loghyperbolic distribution as an alternative to the lognormal distribution. This hypothesis is tested using a set of data from the Denver basin. The results indicate that the loghyperbolic distribution shows a better fit to the empirical data than the lognormal distribution.     

压制50 Hz干扰波的地震资料处理方法

压制50 Hz工业电干扰,通常在频率域采用陷波器进行滤波,该方法在压制50 Hz干扰信号的同时也损伤了有效信号中的50 Hz成分,从而降低了地震资料的品质。利用迭代法对初至波之前的信号进行分析,求取50 Hz干扰波的振幅和相位特性,对50 Hz干扰波进行压制。实际应用效果表明,该方法能够很好地压制50 Hz干扰波,且不对有效信号产生伤害。     

关于数字地质图元数据编制方法若干问题的讨论

为实现空间数据共享,需要描述空间数据或数据集的内容、质量、状态和其他特性的数据,这就是元数据.以编制中国1∶50万数字地质图空间数据库元数据的实际经验,结合国内外已有的资料,分析了数字地质图空间数据库元数据的特点、用途和编制方法提出了进一步改进的建议.     

大数据科学从信息化、模式化到智能化:现代地球化学应用研究的新范式

地球科学领域处在信息科学与信息化社会时代,基于大数据战略驱动的现代地球科学正在蓬勃兴起.诞生于近代的地球化学具有天然的结构化信息科学属性.提出建立从信息化、模式化到智能化的地球化学大数据信息科学应用研究总体思路,即基于地球化学大数据首先建立信息化系统,运用地球系统科学方法理论建立成矿地球化学分带富集模式与生态地球化学累...