Non-linear inversion of scattered seismic surface waves     

Xander Campman  Christina Dwi Riyanti 《Geophysical Journal International》2007,171(3):1118-1125

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A Combined Three-Dimensional Geological-Geostatistical-Numerical Model of Underground Excavations in Rock   总被引：1，自引：1，他引：1  

M. Stavropoulou  G. Exadaktylos  G. Saratsis 《Rock Mechanics and Rock Engineering》2007,40(3):213-243

Summary. This paper exploits geological and borehole geotechnical data obtained in the exploratory phase of a tunneling project to investigate in a first place if the kriging interpolation scheme may effectively reproduce the spatial variability of rock mass quality (Rock Mass Rating, RMR) in the vicinity of tunnels. For this purpose a quick solver in Fortran has been developed that performs variography analysis of 3D spatial data, fast kriging estimations of RMR between borehole sampling locations at the centroids of the elements of the numerical model, and model validation. For the purpose of an integrated underground excavation design, a step further is made by incorporating into the 3D mechanical numerical model of the rock mass, the three-dimensional (3D) solid geological model, thus coupling the geology with the ground (geotechnical) model (i.e. each element of the numerical model is assigned a geological material). The mechanical properties of each finite difference cell (or Representative Elementary Volume) of the ground model were then prescribed according to its geological type, the spatial heterogeneity of the rock mass expressed quantitatively with the kriging model, and the upscaling calculations of the mechanical properties of the intact rocks determined in the laboratory, based on the size-effect (strength dependence on size) and Damage Theory. Furthermore, a preliminary numerical simulation of the advance of unsupported tunnels in the model of the heterogeneous rock mass was performed for illustration purposes.  相似文献   

Source, path and receiver effects on seismic surface waves     

Ana M. G. Ferreira  John H. Woodhouse 《Geophysical Journal International》2007,168(1):109-132

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Mantle lateral variations and elastogravitational deformations – II. Possible effects of a superplume on body tides     

L. Métivier  M. Greff-Lefftz  M. Diament 《Geophysical Journal International》2007,168(3):897-903

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Multi-scale heterogeneity of soil moisture following snow thawing in Haloxylon ammodendron shrubland     

LI Jun  ZHAO ChenYi  ZHU Hong  WANG Feng  WANG LiJuan  KOU SiYong 《中国科学D辑(英文版)》2007,50(Z1):49-55

Spatial variation of soil moisture after snow thawing in South Gurbantunggut was quantitatively studied using ANOVA and geostatistics at various scales. The results show that the soil moisture heterogeneity varies along with spatial scales. At the shrub individual scale, there is a gradient in soil moisture from shrub-canopied area to canopy margin and to the interspaces between shrubs. At the community scale, soil moisture is highly autocorrelated and the semivariogram is fitted as spherical model, with an 89.6% structural variance and a range of 4.02 m. In addition, Kringing map indicates that the soil moisture distribution pattern after snow thawing is highly consistent with the shrub patch pattern. At the typical inter-dune transect scale, soil moisture presents a pattern of high value at inter-dune depression and low value at dune, and this variation is fitted as Gaussian model with a structural variance of 95.8% and a range of 66.16 m. The range is comparable with the scale of topography zoning, suggesting that the topography pattern controls the pattern of snowmelt at this scale. The evidence indicates that the heterogeneity of soil moisture at various scales is controlled by various land surface processes after snow thawing. For Gurbantunggut Desert, the spatial heterogeneity of snowmelt at various scales is ecologically valuable, because it promotes the utilization efficiency of the snowmelt for the desert vegetation.  相似文献   

Modelling Regional Scale Surface Energy Exchanges And Cbl Growth In A Heterogeneous, Urban-Rural Landscape     

H. A. Cleugh  C. S. B. Grimmond 《Boundary-Layer Meteorology》2001,98(1):1-31

Over the last decade, simple models of theconvective boundary layer (CBL) have beensuggested as an approach to inferring regionallyaveraged land-air exchanges of heat, water and tracegases, because the properties of the CBL respond toan average of the underlying small-scaleheterogeneity. This paper explores the use of anintegral CBL method to infer regionally averagedfluxes in a landscape that has at least three majorsources of heterogeneity – irrigated andnon-irrigated rural land use and a large urban area(Sacramento region, California).The first part of the paper assesses the validity ofthe simple slab model of the CBL – this isintegrated forwards in time using local-scalemeasured heat and water vapour fluxes, to predictmixed-layer depth, temperature and humidity. Of thefour different CBL growth schemes used, the Tennekesand Driedonks model is found to give the bestperformance. Evaluation of the model performancewith different weightings of heat and water vapourfluxes based on the land use characteristics in theregion suggest that the source area for theboundary-layer sonde measurements is larger thanphysically-based estimates would suggest.Finally, measured time series of potentialtemperature are used to infer regionally averagedsensible heat fluxes using an integral CBL (ICBL)method. These ICBL fluxes are compared with thosemeasured at the local scale over the three land usetypes that comprise the region of interest. They arefound to be closest to the heat fluxes calculated byappropriately weighting the measured heat fluxes inthe source area calculated for the ICBL. We concludethat the integral CBL budget method providesadequate estimates of regionally-averaged surfaceheat fluxes in a landscape that is characterised bysurface types with distinctly different surfaceenergy budgets.  相似文献   

Seismic image quality beneath strongly scattering structures and implications for lower crustal imaging: numerical simulations     

Francesca Martini  Christopher J. Bean  Sean Dolan  David Marsan† 《Geophysical Journal International》2001,145(2):423-435

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储层岩石表面接触角的不确定性研究   总被引：6，自引：0，他引：6  

张曙光  刘景龙  邓颖 《矿物岩石》2001,21(1):48-51

本文指出，储层岩石表面粗糙，非均质性及高的能量，使我们难以用接触角来量度它的润湿性质，由于储层岩石孔隙结构不符合毛管束模型，使得Laplace公式仅在表现接触角趋于2度或180度时可用于根据毛管压力曲线计算储层岩石的孔径分布，好在由于储层岩石表面粗糙使我们常常会遇到这一极端情况。  相似文献   

Upscaling Uncertain Permeability Using Small Cell Renormalization   总被引：1，自引：0，他引：1  

J. J. Hastings  A. H. Muggeridge 《Mathematical Geology》2001,33(4):491-505

Sedimentary rocks have structures on all length scales from the millimeter to the kilometer. These structures are generally associated with variations in rock permeability. These need to be modeled if we are to make predictions about fluid flow through the rock. However, existing computers are not powerful enough for us to be able to represent all scales of heterogeneity explicitly in our fluid flow models—hence, we need to upscale. Small cell renormalization is a fast method for upscaling permeability, derived from an analogue circuit of resistors. However, it assumes that the small scale permeability distribution is known. In practice, this is unlikely. The only information available about small scale properties is either qualitative, derived from the depositional setting of the reservoir, or local to the wells as a result of coring or logging. The influence of small scale uncertainty on large scale properties is usually modelled by the Monte Carlo method. This is time-consuming and inaccurate if not enough realisations are used. This paper describes a new implementation of renormalization, which enables the direct upscaling of uncertain small-scale permeabilities to produce the statistical properties of the equivalent coarse grid. This is achieved by using a perturbation expansion of the resistor-derived equation. The method is verified by comparison with numerical simulations using the Monte Carlo method. The prediction of expected large-scale permeability and its standard deviation are shown to be accurate for small cell standard deviations of up to 40% of the mean cell value, using just the first nonzero term of the perturbation expansion. Inclusion of higher order terms allows larger standard deviations to be modeled accurately. Evaluation of cross-terms allows correlations of actual cell values, over and above the background structure of mean cell values. The perturbation method is significantly faster than conventional Monte Carlo simulation. It needs just two calculations whereas the Monte Carlo method needs many thousands of realisations to be generated and renormalized to converge. This results in significant savings in computer time.  相似文献   

乾县台地倾斜潮汐测量结果及动态特征     

张惠玲  鲁秀玲 《高原地震》1996,(3)

利用Ｖｅｎｅｄｉｋｏｖ调和分析法分析了乾县地震台１９８３－１９９４年的地倾斜固体潮记录，提取了该地区倾斜固体潮汐因子及其动态变化特征，为地球动力学特别是地球内部结构的深入研究提供了固体潮方面的实测参数。  相似文献