Using an approximation of the three-point Gauss–Hermite quadrature formula for model prediction and quantification of uncertainty     

Jonathan Levy  Murray K. Clayton  Gordon Chesters 《Hydrogeology Journal》1998,6(4):457-468

 Computer models are commonly used by regulators and managers to make predictions regarding groundwater flow and contaminant concentrations at various locations and times. However, the uncertainty associated with those predictions is often overlooked, despite the fact that an assessment of such uncertainty is critical in the formulation of policy decisions. One method of quantifying the uncertainty of model predictions, based on the collective uncertainties of the model parameter input values, is to use an approximation of the three-point Gauss–Hermite quadrature formula. The Gauss–Hermite approximation is a convenient substitute for simple Monte Carlo sampling, because it requires fewer model runs and provides an immediate sensitivity analysis of parameter main effects and two-way interactions. For example, a model with four parameters, each with its own associated uncertainty, needs to be run only 33 times to complete the Gauss–Hermite analysis. For an application to a contaminant-transport model, the Gauss–Hermite approximation compares well to the full method, with considerable savings in computing effort. By comparison, Latin hypercube sampling can be more flexible, but it is more complex to use in some circumstances and cannot as easily generate the detailed sensitivity analysis that the Gauss–Hermite approach offers. Received, October 1997 Revised, August 1998 Accepted, August 1998  相似文献   

Groundwater vulnerability assessment of the SW Trans-Danubian Central Range, Hungary   总被引：3，自引：1，他引：2  

J. Mádl-Szőnyi  L. Füle 《Environmental Geology》1998,35(1):9-18

 The most important karst water reservoir of Hungary is found in the SW Trans-Danubian Central Range, selected as test area for the proposed "system approach" and the application of GIS/ARC-INFO to vulnerability mapping. In addition, a case-study exemplifies the particularities of regional karst-aquifer vulnerability, and moreover the interpretation of data and maps from the very same point of view. The work has resulted in plotting an atlas to be a useful tool in the hands of land-users and waste-disposal managers, helping them to prevent groundwater deterioration. Received: 22 July 1996 · Accepted: 12 September 1997  相似文献   

90年代国际岩石圈计划研究进展     

王军芝  聂高众 《地球科学进展》1998,13(1):27-33

概要地介绍了90年代国际岩石圈计划及其下属任务组和工作委员会的活动情况和研究进展,并报道了可能被纳入该计划的新研究项目。  相似文献   

非饱和土壤溶质迁移转化模型参数优化估算   总被引：4，自引：1，他引：4       下载免费PDF全文

王超  顾斌杰 《水科学进展》2002,13(2):184-190

在分析非饱和土壤中水分和溶质迁移转化规律的基础上,采用与坐标网格相适应的分块连续作用的水动力函数,研究模型参数最优化估算技术.运用Gauss-Newton最小化计算的Levenberg-Marquardt修正法来实现反求模型的迭代问题.该方法被应用于估算一维土柱和二维土槽试验研究模型的参数,探讨了参数给定与估算数量对参数的置信区间和预测效果的影响.经验证表明,参数优化估算技术是可行的,以此参数进行模型预测,其结果是可信的.  相似文献   

辽西早白垩世义县组火山岩的地质特征及其构造背景   总被引：29，自引：10，他引：29  

李伍平  路凤香等 《岩石学报》2002,18(2):193-204

早白垩世义县组火山岩虽辽西地区分布最为广泛的中代火山岩。岩石学、元素－同位素地球化学研究表明，义县组火山岩主要为高钾钙碱性系列，相容元素（Cr,Co,Ni,V等）和大离子亲石元素（如Rb,Sr,Ba等）相对富集，市场强元素（如Nb,Ta,Ti,Zr,Hf等）和放射性元素（U,Th）相对亏损，轻重稀土元素分 馏明显，δEu弱负异常，放射成因的Nd,Sr,Pb同位素较低， 具有板内和活动大陆边缘弧地球化学特点。作者认为辽西早白垩世义县组火山岩起源于富集的岩石圈地幔的部分熔融。岩浆在演化过程中以结晶分异作用为主，伴有少量的地壳混染作用，即AFC过程。结合区域构造，作者认为义县组火山岩形成于板内岩石圈的不均匀拉伸环境，是燕山板内造山作用的产物，与中生代古太平洋板块向欧亚板块俯冲没有直接关系。  相似文献   

Lower lithospheric structure beneath the Trans-European Suture Zone from POLONAISE''97 seismic profiles     

M. Grad  G. R. Keller  H. Thybo  A. Guterch  POLONAISE Working Group 《Tectonophysics》2002,360(1-4):153-168

The large-scale POLONAISE'97 seismic experiment investigated the velocity structure of the lithosphere in the Trans-European Suture Zone (TESZ) region between the Precambrian East European Craton (EEC) and Palaeozoic Platform (PP). In the area of the Polish Basin, the P-wave velocity is very low (Vp <6.1 km/s) down to depths of 15–20 km, and the consolidated basement (Vp5.7–5.8 km/s) is 5–12 km deep. The thickness of the crust is 30 km beneath the Palaeozoic Platform, 40–45 km beneath the TESZ, and 40–50 km beneath the EEC. The compressional wave velocity of the sub-Moho mantle is >8.25 km/s in the Palaeozoic Platform and 8.1 km/s in the Precambrian Platform. Good quality record sections were obtained to the longest offsets of about 600 km from the shot points, with clear first arrivals and later phases of waves reflected/refracted in the lower lithosphere. Two-dimensional interpretation of the reversed system of travel times constrains a series of reflectors in the depth range of 50–90 km. A seismic reflector appears as a general feature at around 10 km depth below Moho in the area, independent of the actual depth to the Moho and sub-Moho seismic velocity. “Ringing reflections” are explained by relatively small-scale heterogeneities beneath the depth interval from 90 to 110 km. Qualitative interpretation of the observed wave field shows a differentiation of the reflectivity in the lower lithosphere. The seismic reflectivity of the uppermost mantle is stronger beneath the Palaeozoic Platform and TESZ than the East European Platform. The deepest interpreted seismic reflector with zone of high reflectivity may mark a change in upper mantle structure from an upper zone characterised by seismic scatterers of small vertical dimension to a lower zone with vertically larger seismic scatterers, possible caused by inclusions of partial melt.  相似文献   

垃圾堆放场氯代脂肪烃对浅层地下水的污染特征初步分析   总被引：12，自引：2，他引：12  

李海明  陈鸿权等 《地球科学》2002,27(2):227-230

研究区是浅层地下水主要补给区，通过区内地下水监测说明，受垃圾淋滤液影响的地下水中氯代烃高值点主要集中在研究区中部；地下水中氯代烃检出值和检出率有季节性变化特征，与垃圾堆放时间和该井距垃圾场堆放场距离有密切关系，堆放时间越长，离垃圾堆放场越近，检出率、检出值越高；对地下水污染的敏感性和影响氯代烃迁移的机理方面进行了分析。  相似文献   

Chlorine in submarine glasses from the Lau Basin: seawater contamination and constraints on the composition of slab-derived fluids     

Adam J.R. Kent  David W. PeateSally Newman  Edward M. StolperJulian A. Pearce 《Earth and Planetary Science Letters》2002,202(2):361-377

Measurements of chlorine concentrations in matrix glasses from 18 primitive (>6 wt% MgO) and eight evolved lavas from active spreading centers in the Lau Basin back-arc system provide insight into the processes which control chlorine concentrations in subduction-related magmas, and can be used to investigate chlorine enrichment related to fluids derived from the underlying subducted slab. Chlorine contents of the glasses are highly variable (0.008-0.835 wt%) and generally high with respect to uncontaminated mid-ocean ridge basalt. Chlorine contents are highest in fractionated lavas from propagating ridge tips and lowest in more primitive basaltic lavas. Two different styles of enrichment in chlorine (relative to other incompatible elements) are recognized. Glasses from the Central Lau Spreading and Eastern Lau Spreading Center typically have low Ba/Nb ratios indicating minimal input of slab-derived components, and high to very high ratios of chlorine relative to K₂O, H₂O, and TiO₂. This style of chlorine enrichment is highest in the most fractionated samples and is consistent with crustal assimilation of chlorine-rich altered ocean crust material. Data from the literature suggest that contamination by chlorine-rich seawater-derived components also characterizes the Woodlark Basin and North Fiji Basin back-arc systems. The second style of chlorine enrichment reflects input from slab-derived fluid(s) to the mantle wedge from the adjacent Tonga subduction zone. Basaltic glasses from the Valu Fa Ridge and Mangatolu Triple Junction show correlations between ratios of chlorine and K₂O, H₂O, and TiO₂ and indices of slab-derived fluid input such as Ba/Nb, Ba/Th and U/Th, consistent with chlorine in these lavas originating from a saline fluid added to the mantle wedge. Within the Valu Fa Ridge the measured range of chlorine contents equates to a chlorine flux of 224-1120 kg/m/yr to the back-arc crust. Using a simple melting model and additional data from other back-arc and arc sample suites we conclude that chlorine is a major component within the slab fluids that contribute to many arc and back-arc melting systems, and probably plays an important role in regulating trace element transport by slab fluids in the mantle wedge. For the back-arc suites we have examined the estimated Cl/H₂O and Cl/K₂O ratios in the slab fluid component correlate with proximity to the arc front, suggesting that progressive dehydration of the slab and/or re-equilibration and transport within the mantle wedge may influence the overall degree of chlorine enrichment within the slab fluid component. The degree of chlorine enrichment observed in most back-arc lavas also appears too great to be explained solely by melting of amphibole, phlogopite or apatite within the mantle source and suggests that chlorine must be present in another phase, possibly a chlorine-rich fluid.  相似文献   

Mantle heterogeneity beneath the southern Mid-Atlantic Ridge: trace element evidence for contamination of ambient asthenospheric mantle   总被引：1，自引：0，他引：1  

P.J le Roux  A.P le Roex  J.-G SchillingN Shimizu  W.W PerkinsN.J.G Pearce 《Earth and Planetary Science Letters》2002,203(1):479-498

We report new trace element data for an extensive suite of quench basalt glasses dredged from the southern Mid-Atlantic Ridge (MAR) between 40°S and 52.5°S. Ratios between highly incompatible trace elements are strongly correlated and indicate a systematic distribution of incompatible element enriched mid-ocean ridge basalt (MORB) (E-type: Zr/Nb=5.9-19, Y/Nb=0.9-8.4, (La/Sm)_n=1.0-2.9) and incompatible element depleted MORB (N-type: Zr/Nb=30-69, Y/Nb=11-29, (La/Sm)_n=0.48-0.79) along this section of the southern MAR. A notable feature of N-type MORB from the region is the higher than usual Ba/Nb (4-9), La/Nb (1.2-2.4) and primitive mantle normalised K/Nb ratios (>1). Ba/Nb ratios in E-type MORB samples from 47.5 to 49°S are especially elevated (>10). The occurrence and geographic distribution of E-type MORB along this section of the southern MAR can be correlated with the ridge-centred Shona and off-axis Discovery mantle plumes. In conjunction with published isotope data for a subset of the same sample suite [Douglass et al., J. Geophys. Res. 104 (1999) 2941], a model is developed whereby prior to the breakup of Gondwana and the opening of the South Atlantic Ocean, the underlying asthenospheric mantle was locally contaminated by fluids/melts rising from the major Mesozoic subduction zone along the south-southwest boundary of Gondwana, leaving a subduction zone geochemical imprint (elevated (K/Nb)_n and ⁸⁷Sr/⁸⁶Sr ratios, decreased ¹⁴³Nd/¹⁴⁴Nd ratios). Subsequent impingement of three major mantle plume heads (Tristan/Gough, Discovery, Shona) resulted in heating and thermal erosion of the lowermost subcontinental lithosphere and dispersal into the convecting asthenospheric mantle. With the opening of the ocean basin, continued plume upwelling led to plume-ridge interactions and mixing between geochemically enriched mantle derived from the Shona and Discovery mantle plumes, material derived from delamination of the subcontinental lithosphere, and mildly subduction zone contaminated depleted asthenospheric mantle.  相似文献   

GIS Techniques for Mapping Groundwater Contamination Risk   总被引：11，自引：0，他引：11  

Ducci  Daniela 《Natural Hazards》1999,20(2-3):279-294

The groundwater contamination risk map of a samplealluvial area was produced by using the IlwisGeographical Information System (GIS) to construct andto overlay thematic maps. The risk map has beenderived from the vulnerability map, the hazard map,where the potential contaminating sources wereidentified, and the socio-economic value of thegroundwater resource, represented by the wells. Thegroundwater quality map allowed thereliability of hazard and risk maps to be tested.The final map shows interesting results and stressesthe need for the GIS to test and improve on thegroundwater contamination risk assessment methods.  相似文献