非穿透裂纹平板试件三维破裂的实验研究

在研究地震孕育及震源破裂的问题时,用三维破裂来模拟地震破裂过程,比二维破裂与实际更加接近。我们设计了一组实验,采用几种不同的材料（玻璃、有机玻璃和大理石等）做成平板试件,在其中心预制非穿透裂纹,并在单轴压下进行了实验研究。 实验结果表明,非穿透裂纹与穿透裂纹的扩展情况有质的差别。非穿透裂纹的扩展并不沿原裂纹面延伸,而是沿裂纹前缘扩展出许多裂纹面,每一个破裂面都是复杂的扭曲、拐折的曲面。这可能意味着实际地震断层的扩展情况也是极为复杂的。     

Full 3-D numerical modeling of borehole electric image logging and the evaluation model of fracture

A full 3-D finite element method numerical modeling program is written based on the principle and technical specification of borehole electric image well logging tool. The response of well logging is computed in the formation media model with a single fracture. The effect of changing fracture aperture and resistivity ratio to the logging response is discussed. The identification ability for two parallel fractures is also present. A quantitative evaluation formula of fracture aperture from borehole electric image logging data is set up. A case study of the model well is done to verify the accuracy of the for-mula. The result indicates that the formula is more accurate than the foreign one.     

含有倾斜薄裂缝孔隙地层中的井孔声场

应用三维交错网格应力-速度有限差分方法,数值模拟了含有倾斜裂缝孔隙介质地层中点声源所激发的井孔声场问题.为满足薄裂缝计算需求,开发了不均匀网格有限差分算法,提高了计算精度及计算速度.利用将孔隙介质方程参数取为流体极限的办法来处理裂缝中的流体,实现了流体-孔隙介质界面处的差分方程统一,使界面处的计算更加灵活方便.在验证了方法正确性的基础上,分别考察了单裂缝宽度、裂缝带宽度、裂缝倾斜角度以及孔隙介质渗透率等参数的变化对井轴上阵列波形的影响并进行了分析.结果表明,声波经过裂缝时可能产生反射横波及斯通利波,后者随裂缝宽度的减小而减小,而前者随裂缝宽度的改变,变化不大,在裂缝很小(20μm)时依然存在;裂缝带的宽度、密度越大,反射斯通利波越强;当裂缝(裂缝带)倾斜时,反射横波消失,但反射斯通利波受裂缝倾斜角度的影响较小;渗透率的改变对斯通利波的衰减影响较为明显.     

Visualizing and interpreting 3-D Euler solutions using enhanced computer graphics

The Euler 3-D deconvolution technique uses potential field data to calculate the position of discontinuities in physical properties without the need of any prior local geological information. Initial difficulties in presenting the Euler solutions in a manner which facilitated interpretation have been overcome using new techniques of image analysis, colour graphics and with real-time rotation of 3-D models. This has provided additional insight into the structure and tectonic history of part of eastern England.     

P-wave Tomography in Inhomogeneous Orthorhombic Media

— A P-wave tomographic method for 3-D complex media (3-D distribution of elastic parameters and curved interfaces) with orthorhombic symmetry is presented in this paper. The technique uses an iterative linear approach to the nonlinear travel-time inversion problem. The hypothesis of orthorhombic anisotropy and 3-D inhomogeneity increases the set of parameters describing the model dramatically compared to the isotropic case. Assuming a Factorized Anisotropic Inhomogeneous (FAI) medium and weak anisotropy, we solve the forward problem by a perturbation approach. We use a finite element approach in which the FAI medium is divided into a set of elements with polynomial elastic parameter distributions. Inside each element, analytical expressions for rays and travel times, valid to first-order, are given for P waves in orthorhombic inhomogeneous media. More complex media can be modeled by introducing interfaces separating FAI media with different elastic properties. Simple formulae are given for the Fréchet derivatives of the travel time with respect to the elastic parameters and the interface parameters. In the weak anisotropy hypothesis the P-wave travel times are sensitive only to a subset of the orthorhombic parameters: the six P-wave elastic parameters and the three Euler angles defining the orientation of the mirror planes of symmetry. The P-wave travel times are inverted by minimizing in terms of least-squares the misfit between the observed and calculated travel times. The solution is approached using a Singular Value Decomposition (SVD). The stability of the inversion is ensured by making use of suitable a priori information and/or by applying regularization. The technique is applied to two synthetic data sets, simulating simple Vertical Seismic Profile (VSP) experiments. The examples demonstrate the necessity of good 3-D ray coverage when considering complex anisotropic symmetry.     

Deduction and application of generalized Euler formula in topological relation of geographic information system (GIS)

Topological relation is one important characteris-tics of spatial data, and reflects the structural relation-ships among geographical objects, and is regarded as the core of spatial data processing[1,2]. Topological transformation has been widely used in diverse spatial studies, and in fact, the processing of geographical data is a kind of topological transformations[3]. There-fore, it is of significance to study the mathematical theory of generating and checking topological rela-tions in GIS…     

Fracture Toughness Measurements and Acoustic Emission Activity in Brittle Rocks

Fracture toughness measurements under static loading conditions have been carried out in Barre and Lac du Bonnet granites. An advanced AE technique has been adopted to monitor real-time crack initiation and propagation around the principal crack in these tests to understand the processes of brittle failure under tension and related characteristics of the resulting fracture process zone. The anisotropy of Mode I fracture toughness has been investigated along specific directions. Microcrack density and orientation analysis from thin section studies have shown these characteristics to be the primary cause of the observed variation in fracture toughness, which is seen to vary between 1.14 MPa.(m)^1/2 and 1.89 MPa.(m)^1/2 in Barre granite. The latter value represents the case in which the crack is propagated at right angles to the main set of microcracks. The creation of a significant fracture process zone surrounding the propagating main crack has been confirmed. Real-time imaging of the fracture process and formation of fracture process zone by AE techniques yielded results in very good agreement with those obtained by direct optical analysis.     

Simplified 3-D dynamic analysis of structures with flexible diaphragms

A simplified method of 3-D dynamic analysis, named 3-D quasi-dynamic analysis, is presented. This method has been primarily used to evaluate stress states at identified times of peak dynamic responses of structures with flexible diaphragms. The quasi-dynamic analysis consists of extracting the accelerations predicted by the time-step integration analyses of two 2-D discrete MDOF dynamic models of a given structure (each discrete model corresponding to one of the principal orthogonal directions of the structure) at given times of interest. These accelerations are imposed on a 3-D representation of the structure (for example, a finite element mesh) as equivalent static forces. Accelerations at the diaphragms are assumed to act over the same tributary areas of the diaphragms considered in the 2-D discrete dynamic models. The study of the firehouse of Gilroy (an unreinforced masonry structure with flexible diaphragms) during the Loma Prieta Earthquake is presented to illustrate the 3-D quasi-dynamic seismic analysis. This method was compared to the more traditional 3-D modal time-step integration and 3-D response spectra analyses. The quasi-dynamic analysis had a general good agreement with the more formal, complex and computationally extensive modal time-step integration analysis. The 3-D response spectra analysis was very conservative and had a poor correlation with both the quasi-dynamic and the modal time-step integration analyses. The case study of the firehouse of Gilroy suggested that if 3-D effects have to be considered in the evaluation of a given structure, the quasi-dynamic analysis constitutes a reliable and computationally cheaper alternative to the more traditional methods of 3-D dynamic analysis.     

不同尺度裂缝对弹性波速度和各向异性影响的实验研究

裂缝广泛分布于地球介质中并且具有多尺度的特点,裂缝尺度对于油气勘探和开发有着重要的意义.本文制作了一组含不同长度裂缝的人工岩样,其中三块含裂缝岩样中的裂缝直径分别为2 mm、3 mm和4 mm,裂缝的厚度都约为0.06 mm,裂缝密度大致相同(分别为4.8%、4.86%和4.86%).在岩样含水的条件下测试不同方向上的纵横波速度,实验结果表明,虽然三块裂缝岩样中的裂缝密度大致相同,但是含不同直径裂缝岩样的纵横波速度存在差异.在各个方向上,含数量众多的小尺度裂缝的岩样中纵横波速度都明显低于含少量的大尺度裂缝的岩样中纵横波速度.尤其是对纵波速度和SV波速度,在不同尺度裂缝岩样中的差异更明显.在含数量多的小尺度裂缝的岩样中纵波各向异性和横波各向异性最高,而含少量的大尺度的裂缝的岩样中的纵波各向异性和横波各向异性较低.实验测量结果与Hudson理论模型预测结果进行了对比分析,结果发现Hudson理论考虑到了裂缝尺度对纵波速度和纵波各向异性的影响,但是忽略了其对横波速度和横波各向异性的影响.     

Determination of a seismometer’s generator constant, azimuth, and orthogonality in three-dimensional space using a reference seismometer

To accurately predict the performance of a seismometer, knowledge of its key parameters is required. We present a new method that requires a single reference instrument to estimate some of the important parameters of the seismometer, such as the ratio of the generator constants, the orthogonality deviation, and the rotation in space and in the horizontal plane with regards to the reference instrument. The procedure is performed in the three-dimensional spaces where the Euler rotation theorem is applied in order to define a transformation, which is then used to transform the detection of the reference seismometer as well as the detection of the instrument under test. The estimated transformation matrix is defined as an upper triangular matrix, where its elements contain the information regarding the parameters of the tested seismometer, which are then evaluated using the Euler angles. The new method has been verified on a pair consisting of two STS-2 seismometers and on a pair consisting of one CMG-3T and one STS-2 seismometer.     

利用地震叠前数据预测火山岩裂缝的方法和效果分析——以松辽盆地北部徐家围子断陷营城组火山岩为例

裂缝问题是火山岩复杂岩性油气藏勘探开发中必须考虑的重要因素之一.火山岩储层裂缝预测的准确性直接影响着油气的产能、钻井工艺和增产改造措施等.本文主要根据等效HTI介质(扩容各向异性介质)的特性,立足地下介质各向异性理论,利用三维地震叠前P波在HTI介质中的属性分布特征来检测裂缝的发育情况.利用三维地震叠前P波裂缝检测技术在松辽盆地北部徐家围子断陷深层营城组火山岩中尝试开展了储层裂缝发育预测研究.通过研究建立了火山岩裂缝地震叠前预测方法,并对营城组火山岩裂缝发育情况进行预测,结果表明裂缝主要分布在工区中部构造高部位,发育方向以北北西向为主.最后利用测井资料和钻井产能资料等进行效果分析,证实该技术对于认识火山岩储层裂缝发育具有实际应用价值,说明应用地震资料开展储层裂缝预测具有横向分辨率高、实现井间分布描述和宏观空间分布规律清楚等特点.     

The task of reconstructing the motion of an object by magnetic measurements

We examine the problem of determining the spatial position of a triaxial magnetometer onboard an artificial satellite by measuring the fields in orbit. Such a task is interesting from the point of view that to solve it, data on the satellite and the character of its motion in orbit are not used. We obtain explicit expressions for the Euler angles via the field components measured in orbit and taken from a field model, which is considered given.     

复杂性颌面外伤的三维CT诊断

本文用３Ｄ９８软件对２２例复杂性颌面外伤常规ＣＴ扫描数据进行三维ＣＴ重建，讨论了三维ＣＴ诊断颌面外伤的优越性，提出尽管三维ＣＴ在骨折探测方面不及二维ＣＴ，但三维ＣＴ在评价骨折的形态，范围，骨折块移位及骨折所致的面部畸形方面优于常规ＣＴ，它是对二维ＣＴ的重要     

Mechanical analysis of en echelon structure and its significance of controlling earthquakes

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2.5-D modeling in electromagnetic methods of geophysics

Understanding, using, or eliminating three-dimensional (3-D) effects in electromagnetic methods of geophysics are critical requirements. Numerous achievements in 3-D modeling sometimes give the impression that they are widely available today in geophysical practice. This is not necessarily true. Existing 3-D modeling packages prove that we know how to perform 3-D modeling. However, the computer resources and costs involved make the practical application of 3-D EM modeling in geophysical applications very limited.A practical compromise, or even alternative, is represented by 2.5-D modeling characterized by the use of a 3-D source in a 2-D medium. This combination allows one to mathematically describe the related boundary value problem as a sequence of independent two-dimensional problems. The typical technique leading to such a split formulation is Fourier analysis. That is why the individual terms of a split solution are often referred to as harmonics.Although each independent problem is two-dimensional, the algorithmic implementation of finite differences or integral equations for the higher harmonics has some specific features not present in the classical 2-D cases. In this paper, a hybrid scheme consisting of a combination of the finite difference technique with the integral equation approach for transient fields is described. Evaluation of algorithm accuracy is presented and a transient logging technique application is considered. The algorithm is fast and easily implemented on a personal computer     

断层交汇区附近的变形特点与声发射特点的实验研究

把昌平花岗岩切割成20多种含两组断层交汇情况的模型.断层物质用2毫米厚的石膏模拟.模型受单轴应力的作用.实验中得出四种破裂组合情况:1.滑动破裂型 发生在两组断层与主压应力轴1的交角一组大于45,一组小于45的情形下.其中,当断层物质石膏湿度为10——15%时,先在大角度面上产生剪切破裂,后沿小角度面产生最终磨擦滑动.在应力位移曲线上表现为两次应力降.当断层物质石膏湿度小于5%时,则只沿小角度面上产生磨擦滑动.应力位移曲线为单应力降。2.压楔型 发生在两组断层与1夹角均大于45的情况下.其应力位移曲线为阶梯式上升型.断层位移方向反复.3.张楔型 发生在两组断层与1夹角均不大于30时.应力位移曲线为单应力降.4.双滑或双破型 发生在两组断层与1夹角均在30和45之间.应力位移曲线为连续的两次应力降.根据应力位移曲线和应力声发射累积数曲线的相似性,主破裂前的声发射累积数与主破裂时峰值应力的相似性以及断层组合与声发射组合的关系中,看出声发射过程对构造条件是敏感的.文中还对不同断层组合下可能出现的地震前兆进行了讨论.      

Radiated seismic energy and strain energy release in laboratory dynamic tensile fracture

Tensile dynamic fractures were propagated under two experimental congifurations for the purpose of assessing the relative amount of strain energy release that is consumed as fracture energy and radiated as seismic waves. The configurations used were (1) application of localized thermal stresses to 2.29 mm-thick plates of soda-lime glass and (2) double cantilever beam (DCB) experiments in 12.7 mm-thick glass plates, in which a fracture is propagated from a notch at one end of the specimen by application of a transverse load. Fracture propagation velocities of 0.35–2 mm/s were obtained for fractures in the first configuration. A capacitance transducer with a point-like probe was used for measuring the seismic displacement waveforms from propagating fracture sources. This transducer is capable of measuring absolute surface displacements with a resolution of 0.01 nm. It has a flat frequency response in the range 10 kHz to 6 MHz. Measured seismic efficiencies, or the ratio of radiated seismic energy to strain energy released, are in the range 10^–5 to 10^–3.     

Network properties of a two-dimensional natural fracture pattern

The influence that fractures exert on the permeability of a fractured rock is, to a large extent, controlled by the nature of the network formed by the fracture system. Here, the network properties of a two-dimensional natural pattern, mapped from the surface of a sandstone layer, are investigated and compared to those of realizations of spatially randomly distributed line segments with similar orientation and length distributions and line segment density (line length per unit area) to the natural pattern. These patterns are composed of clusters of varying size and shape, made up of interconnected fracture traces or line segments. Comparing the natural pattern with the realizations, the natural pattern was found to contain roughly half the number of clusters while the mass (total line length) of the largest cluster is approximately double that of the realizations. The size of the largest cluster controls the connectivity of the patterns, as can be seen by comparing the largest cluster of the natural pattern, which connects all four sides of the region, with those of the realizations, which are unconnected or connect only two sides. Cluster scaling characteristics were found to be similar in the natural pattern and the realizations and show a crossover from a dimension of one (their topological dimension) to two (the dimension of the embedding medium) at a point that corresponds to the fracture spacing. An investigation of the self-similarity dimension, using the box-counting method, showed similar characteristics with a broad transition zone between one- and two-dimensional behaviour at smaller box sizes. The patterns are therefore found to be non-fractal. The effect of the spatial distribution shown by the natural pattern is thus to modify the manner in which fractures are distributed among clusters, increasing connectivity (and permeability in the case of open fractures), but does not affect the cluster scaling characteristics or the self-similarity dimension of the fracture patterns.