双向压缩条件下非均匀断层标本变形过程中的声发射活动特征   总被引：2，自引：0，他引：2       下载免费PDF全文

蒋海昆  马胜利  周焕鹏  侯海峰  戴磊  郑建常 《地震学报》2006,28(3):295-304

在双向压缩条件下,研究了一种非均匀断层模型标本在变形过程中的声发射(AE)时空特征.结果表明,随侧向应力sigma;2的增大,断层破裂强度提高,自加载至破坏的时间延长,破坏形式由突发失稳逐渐转变为渐进式破坏.预制断层及其非均匀性对标本变形过程中AE空间分布图象起明显的控制作用.预制断层,特别是预制断层上的强度不均匀部位及高强度段落,控制着微破裂空间分布的总体格局.破裂局部化均起始于断层上强度不均匀部位,随侧向应力sigma;2的增大,微破裂密集区域从预制断层强度不均匀部位逐渐扩展到整个高强度区段.侧向应力sigma;2的大小对AE时序特征具有显著影响.较低sigma;2条件下,断层表现为突发失稳,失稳发生在微破裂活动ldquo;增强-平静rdquo;的背景之上;而较高sigma;2条件下,断层表现为渐进式破坏,破坏前后AE频次持续增加,AER呈指数增长.sigma;2对b值变化也具有一定影响.当断层破坏表现为突发失稳时,b值在弹性阶段后期至弱化阶段显示出ldquo;前兆rdquo;性降低;而当断层表现为渐进式破坏时,b值变化平稳.   相似文献   

Grain size and grain shape analysis of fault rocks   总被引：4，自引：0，他引：4  

Rene Heilbronner  Nynke Keulen 《Tectonophysics》2006,427(1-4):199

  相似文献   

The log-normal distribution for hydraulic conductivity of compacted clays: Two or three parameters?     

Huaming Zhai  Craig H. Benson 《Geotechnical and Geological Engineering》2006,24(5):1149-1162

Risk and uncertainty assessments for waste containment systems employing clay barriers often include spatial variability in the hydraulic conductivity as part of the analysis. The two-parameter log-normal distribution is often used to describe the spatial variability, but for compacted clays the three-parameter form can be more appropriate. A statistical hypothesis test was developed that can be used to determine if the two- or three-parameter form of the log-normal distribution is more appropriate. The test is based on a likelihood ratio, comparing likelihood functions for the two- and three-parameter forms at their maximums. Likelihood functions are used assuming that a data set can be segregated into a set of distinct groups of hydraulic conductivities. A step-by-step calculation procedure is described and the test is applied to data collected from 45 sites.  相似文献   

Dissolved trace elements in river water: spatial distribution and the influencing factor, a study for the Pearl River Delta Economic Zone, China   总被引：1，自引：0，他引：1  

T. P. Ouyang  Z. Y. Zhu  Y. Q. Kuang  N. S. Huang  J. J. Tan  G. Z. Guo  L. S. Gu  B. Sun 《Environmental Geology》2006,49(5):733-742

Twenty-nine water samples were collected from different river channels of the Pearl River Delta Economic Zone, China. An inductively coupled plasma-mass spectromonitor (ICP-MS) was used to measure concentrations of the trace elements in these samples. The results suggest that the average concentrations of rare earth elements in river water show an increasing trend from the West River, the North River, the rivers of the Pearl River Delta, and the Shenzhen River to the East River. Relatively high concentrations of heavy metals appear in the East River, the rivers of the Pearl River Delta and the Shenzhen River, while the West River and the North River have relatively low heavy metal concentrations. Trace element concentrations in samples collected near urban or industrial areas are much higher than those of samples collected from distant areas, away from urban and industrial areas. After natural conditions, human activities have significant influence on the trace element concentrations in river water. This trace element concentration’s spatial distribution in the river water from the Pearl River Delta Economic Zone is actually an integrated effect of natural conditions and human activity.  相似文献   

Patterns in the Turkish reinsurance claim data, 1998–2002: An application of the extreme value theory     

B. Burçak Başbuğ  Henry P. Wynn 《Natural Hazards》2006,39(2):329-342

The devastating 1999 Marmara and Düzce earthquakes led to a significant increase in the earthquake studies in Turkey in geological, engineering and financial aspects. Extreme Value Theory (EVT) has a range of applications from stock market changes to natural disasters like floods and hurricanes. Here EVT is fitted to the ordinary and earthquake reinsurance claims of Turkey.  相似文献   

Vertical distribution and water solubility of phosphorus and heavy metals in sediments of the St. Lucie Estuary, South Florida, USA   总被引：2，自引：0，他引：2  

Z. L. He  M. Zhang  P. J. Stoffella  X. E. Yang 《Environmental Geology》2006,50(2):250-260

Accumulation and distribution of heavy metals and phosphorus in sediments impact water quality. There has been an increasing concern regarding fish health in the St. Lucie Estuary, which is related to increased inputs of nutrients and metals in recent decades. To investigate vertical changes of contaminants (P, Cd, Cr, Co, Cu, Ni, Pb, Zn, and Mn) in sediments of the St. Lucie Estuary in South Florida, 117 layer samples from six of the 210 to 420 cm depth cores were analyzed for their total and water-soluble P and heavy metals, clay, total Fe, Al, K, Ca, Mg, Na, and pH. Principal component analysis (PCA) was used in two sets of analytical data (total and water-soluble contaminant concentrations) to document changes of contaminants in each core of sediments. The PCA of total contaminants and minerals resulted in two factors (principal components). The first and second factors accounted for 61.7 and 17.2 % of the total variation in all variables, and contrast indicators associated with contaminants of P, Cd, Co, Cr, Ni, Pb, Zn, and Mn and accumulation of Fe and Al oxides, respectively. The first factor could be used for overall assessment of P and heavy metal contamination, and was higher in the upper 45–90 cm than the lower depths of each core. The concentrations of P and heavy metals in the surface layers of sediments significantly increased, as compared with those in the sediments deeper than 45–90 cm. The PCA of water-soluble contaminants developed two factors. The second factor (Cu–P) was higher in the upper than the lower depths of the sediment, whereas the highest score of the first factor (Cd–Co–Cr–Ni–Pb–Zn–Mn) occurred below 100 cm. The water-soluble Cu and P concentrations were mainly dependent on their total concentrations in the sediments, whereas the water-soluble Cd, Co, Cr, Ni, Pb, Zn, and Mn concentrations were mainly controlled by pH.  相似文献   

位场自动反演技术的研究现状及意义   总被引：4，自引：0，他引：4  

张季生 《地球学报》2006,27(6):609-612

本文首先叙述了重、磁异常自动反演技术的特点。与传统的定性分析重、磁场分布特征的方法不同,重、磁异常自动反演方法通过反演得到地下场源分布,即地下密度或磁性的分布特征。由于密度体或磁性体与地质体的关系更为直接,因此这种新一代重、磁解释成果及图件将成为人们从新的角度来认识地质构造的基础材料。文中不但阐述了该方法的研究现状,同时也说明了存在的问题。  相似文献   

南极普里兹湾夏季海冰边缘区内破碎海冰的分布特征          下载免费PDF全文

卢鹏  李志军  张占海  董西路 《水科学进展》2007,18(6):884-892

基于中国第21次南极考察中获得的69°00'S、76°24'E附近普里兹湾夏季海冰边缘区内破碎海冰的航拍照片,利用图像处理的方法从中提取了破碎海冰的若干几何参数,得到了海冰边缘区内随着与开阔水域距离增大,海冰面积、平均钳测直径等几何参数的变化规律。并按其尺寸的变化规律将海冰边缘区划分为边界区、过渡区和内部区三部分,其变化和波浪在冰边缘区中的衰减过程紧密相关。圆度的变化则说明海冰边缘区中海冰磨损最充分的地方是在冰间相互作用最明显的过渡区。另外,一种改进的幂函数分布和Weibull分布用来对破碎海冰尺寸的累积频率进行拟合,分布函数中各参数的变化情况很好的反映了海冰边缘区内破碎海冰的分布变化。其中,参数L_r随着与开阔水距离增加而增大(说明由于波能衰减导致可以出现的破碎海冰最大尺寸的增加);尺度参数L₀随着与开阔水距离增加而增大(反映了破碎海冰平均尺寸的增加以及由于波能的衰减而导致单位面积区域内尺寸较大的破碎海冰所占比例的增加);分布维数D随着与开阔水距离增加而减小(说明了由于波能的衰减导致破碎海冰所受约束条件的减弱);形状参数γ随着与开阔水距离增加而减小(说明了随着波能的衰减破碎海冰尺寸分布范围的增大)。  相似文献   

A case study to verify methods for estimating transmissivity distributions along boreholes     

Åsa Fransson 《Hydrogeology Journal》2007,15(2):307-313

Two methods, both using data from fixed-interval-length hydraulic tests and geological mapping on different scales, have been utilised to estimate transmissivity distributions of individual fractures. Individual fracture properties are of importance in estimating transport of water and solutes; they influence the spreading of grout when sealing tunnels. One of the methods is non-parametric, while the other is based on combinatorics and the multiplication principle. The study verified the usefulness of both methods for estimating the probability of conductive and non-conductive fractures, and the transmissivity distributions. Data for estimating transmissivity distributions originate from flow logging of a borehole in Sweden. Fracture frequency data are from core logging and images using a borehole image processing system (BIPS). Estimated transmissivity distributions, based on flow log data from 3-m sections (test scale length, L: 3 m, and step length, dL: 3 m), were compared with transmissivities obtained directly from detailed, overlapping flow logging which identify individual conductive fractures (test scale, L: 0.5 m, step length, dL: 0.1 m). The latter data are considered to be an acceptable approximation of the individual fracture transmissivities; the agreement, compared with the calculated transmissivity distributions based on 3-m section data, is good for both methods.

---

Resumen Se han utilizado dos métodos, ambos procesando datos de pruebas hidráulicas de longitud e intervalo fijo y mapas geológicos en distintas escalas, para estimar las distribuciones de transmisividad de fracturas individuales. Las propiedades de fracturas individuales son de importancia para estimar el transporte de agua y solutos; las propiedades influyen en la propagación de lechada al sellar túneles. Uno de los métodos es no paramétrico mientras que el otro se basa en el principio de multiplicación y combinatorio. El estudio verifica la utilidad de ambos métodos para estimar la probabilidad de fracturas conductivas y no conductivas y las distribuciones de transmisividad. Los datos para estimar las distribuciones de transmisividad se originan del registro de flujo de un pozo en Suecia. Los datos de frecuencia de fracturas provienen de registros de núcleo e imágenes usando un Sistema de Procesamiento de Imágenes de Pozo (BIPS). Se compararon las distribuciones estimadas de transmisividad basadas en datos del registro de flujo en secciones de 3 m (longitud de escala de la prueba L: 3 m, y escalón de longitud dL: 3 m), con transmisividades obtenidas directamente de registros detallados de flujo superpuesto el cual identifica fracturas conductivas individuales (escala de la prueba, L: 0.5 m, escalón de longitud, dL: 0.1 m). Los últimos datos se consideran una aproximación aceptable de las transmisividades de fracturas individuales; la consistencia, comparada con las distribuciones de transmisividad calculada basadas en datos de sección de 3 m, es buena para ambos métodos.

---

Résumé Deux méthodes ont été testées afin d’estimer la distribution des transmissivités de fractures unitaires; toutes deux utilisent des données issues de tests hydrauliques effectués à intervalles réguliers et de cartographies géologiques à plusieurs échelles. La connaissance des propriétés des fractures unitaires est importante pour estimer le transport d’eau et de solutés; elles influencent en outre l’étalement du coulis lors du scellement des tunnels. La première méthode est non-paramétrique, et la seconde repose sur l’analyse combinatoire et le principe de multiplication. Cette étude a vérifié l’utilité des deux méthodes pour estimer la probabilité d’occurrence de fractures conductrices et non-conductrices, et la distribution des transmissivités. Les distributions des transmissivités ont été estimées à partir de diagraphies effectuées sur un forage situé en Suède. Les densités de fracturation proviennent de carottages et d’imagerie BIPS (Borehole Image Processing System). Les distributions estimées des transmissivités, basées sur des diagraphies de flux effectuées sur des sections de 3 m (échelle du test L:3 m; pas dL:3 m), ont été comparées aux transmissivités obtenues sur des diagraphies de flux détaillées et se chevauchant, identifiant les fractures conductrices unitaires (échelle du test L: 0.5 m ; pas dL: 0.1 m). Il est admis que ces dernières données représentent une approximation satisfaisante des transmissivités des fractures unitaires; les deux méthodes sont en accord avec les distributions des transmissivités calculées à partir des données acquises sur des sections de 3 m.

  相似文献   

Application of bivariate extreme value distribution to flood frequency analysis: a case study of Northwestern Mexico   总被引：1，自引：0，他引：1  

Carlos Escalante-Sandoval 《Natural Hazards》2007,42(1):37-46

In Mexico, poverty has forced people to live almost on the water of rivers. This situation along with the occurrence of floods is a serious problem for the local governments. In order to protect their lives and goods, it is very important to account with a mathematical tool that may reduce the uncertainties in computing the design events for different return periods. In this paper, the Logistic model for bivariate extreme value distribution with Weibull-2 and Mixed Weibull marginals is proposed for the case of flood frequency analysis. A procedure to estimate their parameters based on the maximum likelihood method is developed. A region in Northwestern Mexico with 16 gauging stations has been selected to apply the model and regional at-site quantiles were estimated. A significant improvement occurs, measured through the use of a goodness-of-fit test, when parameters are estimated using the bivariate distribution instead of its univariate counterpart. Results suggest that it is very important to consider the Mixed Weibull distribution and its bivariate option when analyzing floods generated by a␣mixture of two populations.  相似文献