基于球面边值问题的点质量调和分析方法

对全球扰动点质量模型而言,可以假定虚拟扰动质点系位于地球内部同一Bjerhamar球面上,同时把边值界面视为球面.本文针对这一假设下所形成的线性方程组的系数阵,运用快速傅里叶变换的方法,得到了点质量模型解算中利用分块循环矩阵分解大型线性方程组的新方法.全球30′×30′扰动点质量模型259200阶方程组的解算分解为720个360阶方程组的解算,解决了点质量模型构建中大型线性方程组的稳定解算问题.推导了全球点质量模型与球谐位系数模型的转换关系,得到了一种基于球面边值问题的点质量调和分析方法.数值模拟试验表明,在适当选取点质量埋深度的情况下,本文的点质量调和分析方法较传统的调和分析方法精度更高.     

外部扰动重力场的频谱响应质点模型

本文提出一种新的虚拟质点建模方式，旨在实现地球外部重力场的快速精密赋值．其基本思想在于：根据内部场源与外部场的频谱响应关系，视质点系为若干子系组成，让其中每个子系具有与外部场的相应频段分量响应的谱频特性．质点系的频谱响应性质将会大大削弱通常质点模型产生的所谓且Ｒｕｎｇｅ现象：泄漏与增频，从而显著提高逼近精度．文中还详细讨论了频谱响应质点模型的原理和构制方法，并对模型精度进行了分析和估算．     

The effect of the irregularities of the shape of the Earth's core-mantle boundary on the observed acceleration of gravity

Summary The disturbing gravitational effect of the irregularities of the shape of the coremantle boundary are studied at a point on the Earth's surface. The effect is computed for models of local and zonal distribution of the disturbing masses under the assumption that the total mass of the Earth remains constant. Formulae giving the disturbing gravitational effect as a function of the distribution of the disturbing masses and of the position of the point of observation on the Earth's surface are derived for the individual models. Numerical values of the disturbances have been calculate in all cases.     

Regional gravity field modeling using free-positioned point masses

A two-step free-positioned point mass method is used for regional gravity field modeling together with the remove-compute-restore (RCR) technique. The Quasi-Newton algorithm (L-BFGS-B) is implemented to solve the nonlinear problem with bound constraints in the first step, while in the second step the magnitudes of the point masses are re-adjusted with known positions in the least-squares sense. In order to reach a good representation of the gravity field, a number of parameter sets have to be defined carefully before the computations. The effects of four important parameter sets (depth limits, number of point masses, original/reduced basis functions and optimization directions) are investigated for regional gravity field modeling based on two numerical test cases with synthetic and real data. The results show that the selection of the initial depth and depth limits is of most importance. The number of point masses for obtaining a good fit is affected by the data distribution, while a dependency on the data variability (signal variation) is negligible. Long-wavelength errors in the predicted height anomalies can be reduced significantly by using reduced basis functions, and the radial-direction optimization proves to be stable and reliable for regular and irregular data scenarios. If the parameter sets are defined properly, the solutions are similar to the ones computed by least-squares collocation (LSC), but require fewer unknowns than LSC.     

The 3-D Truncation Filtering Methodology Defined for Planar and Spherical Models: Interpreting Gravity Data Generated by Point Masses

This paper focuses on one particular way of linear filtering the gravity data to facilitate gravity inversion or interpretation. With the use of integral transforms the gravity anomalies are transformed into new quantities that allow an easier interpretation with the help of pattern recognition. As the integral transforms are in fact filters, and as the regions of integration are caps with a variable radius, which can be systematically changed as a free parameter, we refer to such methodology as the truncation filtering. Such filters may be understood as weighted spherical windows moving over the surface, on which the gravity anomaly is defined, the kernel of the transform being the weight function. The objective of this paper is to define and deploy the truncation filtering for a planar model, i.e. for a homogenous horizontally infinite layer with embedded anomalous masses, and for a spherical model, i.e., for a homogenous massive sphere with embedded anomalous masses. Instead of the original gravity anomaly, the quantities resulting from the truncation filtering are interpreted/inverted. As we shall see, this approach has certain benefits. The fundamental concept of the truncation filtering methodology is demonstrated here in terms of the model consisting of one point mass anomaly.The relationship between the depth of the point mass and the instant of the onset of the dimple pattern observed in sequences produced by truncation filtering the synthetic gravity data generated by point masses is, for both the planar and spherical models, compiled by computer simulations, as well as derived analytically. It is shown, that the dimple pattern is a consequence of truncating the domain of the filter and is free of the choice of the kernel of the filter. It is shown, that in terms of the mean earth and depths of point masses no greater than some 100 km the spherical model may be replaced by a planar model from the perspective of the truncation filtering methodology. It is also shown, that from the viewpoint of the truncation filtering methodology the rigorous gravity anomaly may be approximated by the vertical component of the gravity disturbance. The relationship between the instant of the dimple onset and the depth of the point mass thus becomes linear and independent of the magnitude (mass) of the point mass.     

Generalized Solutions of the Inverse Problem and New Technologies for the Quantitative Interpretation of Gravity Anomalies

The approach, fundamentally different from the known ones, to estimating the spatial location of the domain filled with the disturbing masses based on the gravity field measurement data is suggested. The main idea of the approach is, using the set of the probable variants of the interpretation, to construct the distribution of a certain parameter associated with the estimate of probability of detecting the sources of the field in any point of the studied geological medium and then to apply this distribution to each domain eligible for being the true carrier of the anomalous masses. These constructions yield the generalized admissible solutions of the inverse problem with ranking the separate fragments of the model carrier in terms of the probability of detecting anomalous masses in them.     

Variations in the index of refraction of the atmosphere

Summary This paper discusses the atmospheric refractive index (a) throughout the year at the surface of the earth and (b) for each season in various air masses. Mean monthly or seasonal values, respectively, are employed.The annual variation in the refractive index at the earth's surface is examined by noting the contributions of the optical and the water vapor terms. The former exhibits a sinusoidal variation with a period of a year, having a maximum in winter and a minimum during summer. The amplitude of the cycle is latitude dependent, appearing greater in polar than in tropical regions. The magnitude of the water vapor term is more strongly dependent upon both season and latitude. Excepting areas where the dew point changes little from month to month, the water vapor term attains a single yearly maximum at about mid July.Graphs of the variation of refiactive index with altitude for the major air masses are included. Highest values of the index up to a height of 6 km are found in tropical maritime and monsoon air masses; lowest values, in arctic air masses. The rate of decrease of refractive index with height is usually quite different for diverse air masses. From the surface to an altitude of 6 km, the most constant rate of decrease with altitude, considering all air mass types, was found in the superior air mass.     

Structural Analysis of Water Quality Formation in an Urban Watercourse: Point,Non-Point,Transit, and Natural Components

The decomposition of water quality formation of city watercourse was carried out. The ratio of natural and anthropogenic (local and transit) components of the watercourse water quality were determined in the case of the Belaya River. The mass of pollutants entering the water body from Ufa City territory through sources of different categories, including point and non-point, was estimated. It was established that the ratio of pollutant masses from point and non-point sources varies in different phases of water regime, depending on the pollutant type. In the study, it is shown that the system of river water quality monitoring should be improved taking into account the features of its formation within urban territory.     

全球强震活动纬度分布特征及其解释

利用1900年以来全球M_S≥7.0地震目录, 分析了全球强震随纬度分布特征, 得到的结果显示: 全球强震主要分布在35°S~65°N之间, 中心点在15°N附近, 而非以赤道为对称点的分布; 在0°~180°W之间的地震, 主要分布在45°S~15°N之间, 中心点在15°S附近; 在90°W~90°E之间的地震, 主要分布在40°S~40°N之间, 中心点在赤道附近; 在0°~180°E之间的地震, 主要分布在25°S~55°N之间, 中心点在15°N附近。 分析表明, 全球强震的纬度分布特征与潮汐引起的地球自转动能变化随纬度的分布具有很好的一致性, 说明地震的发生与地球自转动能有关。 由于地球自转速率变化, 将引起不同质量的地球岩石圈块体之间产生相互作用(非弹性碰撞), 这种相互作用可能是引起地震的主要成因之一。 非弹性碰撞会造成块体动能的损失, 地震所释放的能量就来自于所损失的动能。     

岩体构造层次及其力学行为

研究了岩体的构造层次与其力学行为之间的关系。从分析可以看出，岩体的强度与岩体的构造层次之间有紧密的关系。岩体的构造层次越小．在本层次上强度越高。因此岩体的最小工作层次与外力所能达到的水平之间有直接的联系。表现在破坏块体的尺寸上，最小的破坏尺寸与所能达到的强度有直接的关系。在此基础上得到了破坏块体的尺寸与应变率，塑性变形及应力状态之间的关系。     

Use of non-linear localization for isolating structures from earthquake-induced motions

The dynamic response due to earthquake-induced excitations of multi-storey buildings simulated by a cantilever (with attached concentrated masses) supported on a flexible foundation, is reconsidered when stiffness non-linearities are included. To this end, a suitable non-linear spring-mass device is placed between the ground and the mass of the foundation, which under certain conditions can absorb a significant amount of seismic energy over a large frequency range, thus drastically reducing the seismic response of the foundation. This is achieved by the stiffness non-linearity that gives rise to a localization phenomenon, according to which motions generated by external disturbances remain passively localized close to the point of seismic excitation instead of ‘spreading’ to the entire structure. The implications of these findings to the design of earthquake-resistant structures are discusssed. Copyright © 1999 John Wiley & Sons, Ltd.     

基于无人机摄影测量技术的地震地表破裂带定量参数提取 ——以1709年中卫南M7½地震为例

本文首先介绍了无人机摄影测量技术获取数字高程模型(digital elevation model,缩写为DEM)和地貌数据(正射影像)的作业流程,对比分析了三种不同质量密集点云生成的DEM在水平位置和高程上的差异;然后以1709年中卫南M7?大地震的主体地表破裂带为例,提取其上地震断层的垂直位错量和水平位移量.研究结果...     

Sprungschichtneigung im Zürichsee durch Sturm

Summary During the thermocline tilt, observed in November 1947 in Lake Zürich, a difference in level of 16 m was found between the highest point (Quaibrücke) and the equivalent lowest point (middle of the Lake St?fa-Ufenau). The “fulcrum” line of this tilt was found somewhat N. of the deepest point and probably ran somewhat diagonally across the lake (e. g. Herrliberg-Rüschlikon) as a result of the angle between the W. wind and the longitudinal axis of the lake. Westerly storms, lasting for four days, transported enormous masses of warm, oxygen- and plankton-rich surface water up the lake; while hypolimnion water streamed down the lake in depths of 20 to 60 m. Attention is drawn to the physical and biological effects and to the frequency of these wind-induced drifts, which certainly should receive more attention in Swiss lakes.      

The acoustic emission from rock under stress and hydraulic pressure

The essential conditions for effective and ecologically safe exploitation of underground waste storage are maintenance, prevention, and monitoring of tightness of rock masses covering and surrounding the reservoir rock complex. This monitoring can be realized by a especially designed acoustic measurement system.The reservoir rock complexes - without leakage - are supposed to be in physical equilibrium; without changes of rock dynamic properties the acoustic emission vanishes. In contrast, as is shown, the results of the field tests carried out in coal mines proved that there was a correlation between the stresses and the acoustic emission ratio. The laboratory experiments also showed correlation between changes of permeability of coal samples and acoustic emission.the explanation of the observed results is based on the development of inelastic deformation of a rock skeleton. The plastic strains in the porous rock appear after overcoming the yield point. The yield point value can be extended by increase of shear stresses, effective stresses and interstitial pressure.In particular, there are three kinds of dynamic phases which may appear preceding the failure of leak tightness:

1. (1) breaking of the rock masses due to stress (Griffith criterion of stability may be expressed in terms of the acoustic emission parameters),

2. (2) the dilatant corrosion of pressure plasticity resulting from chemical, physical and thermal activities, and

3. (3) the destructive increase of pressure in rock pores.

This paper presents the statistical parameters describing the acoustic emission from the rock mass and the dynamic processes mentioned above are described in terms of seismoacoustic activity.     

Influence of geostatic stresses on permeability of jointed rock masses

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Coupled finite element and discrete element method for underground blast in faulted rock masses

This paper focuses on the propagation and dynamic effects of blast waves in faulted rock masses. A coupled method combining UDEC and LS-DYNA is presented whereby the explosion process is simulated by LS-DYNA while the wave propagation and its dynamic effects in rock masses with faults are modeled by UDEC. The blast-induced crack evolution and failure zone distribution in faulted rock masses are explored using the proposed coupled method. The relationship between rock failure and fault parameters such as dip, stiffness and friction are also investigated. The results indicate that the coupled method is feasible and effective for evaluating explosion in discontinuous rock system and the existence of faults exerts significant influence on the pattern of rock masses failure.     

弹性波CT技术在大足石刻岩体破碎带探测中的应用

大足石刻是中国现存的重要石质文物之一,具有重要的历史和文化价值,其中有的石刻造像曾被列为国家石质文物保护“一号工程”;最近,文物保护部门又启动了对危岩体的加固和防渗工程。为确定大足石刻宝顶山大佛湾岩体中破碎带发育情况,应用跨孔弹性波CT技术对指定位置的工程岩体进行了探测。CT探测得到的岩体弹性波速成像清楚地揭示了两个钻孔之间岩体中破碎带的规模和产状,与岩体所在的区域地质构造应力场作用协调一致,证明了探测成像结果的可靠性,为大佛湾岩体的渗流和稳定性评估提供了依据。      

Mitigation of railway induced ground vibration by heavy masses next to the track

The effectiveness of heavy masses next to the track as a measure for the reduction of railway induced ground vibration is investigated by means of numerical simulations. It is assumed that the heavy masses are placed in a continuous row along the track forming a wall. Such a continuous wall could be built as a gabion wall and also used as a noise barrier. Since the performance of mitigation measures on the transmission path strongly depends on local ground conditions, a parametric study is performed for a range of possible designs in a set of different ground types. A two-and-a-half dimensional coupled finite element–boundary element methodology is used, assuming that the geometry of the problem is uniform in the direction along the track. It is found that the heavy masses start to be effective above the mass–spring resonance frequency which is determined by the dynamic stiffness of the soil and the mass of the wall. At frequencies above this resonance frequency, masses at the soil׳s surface hinder the propagation of surface waves. It is therefore beneficial to make the footprint of the masses as large and stiff as possible. For homogeneous soil conditions, the effectiveness is nearly independent of the distance behind the wall. In the case of a layered soil with a soft top layer, the vibration reduction strongly decreases with increasing distance from the wall.     

A Study on Confined Flow of Ground Water Through a Tunnel

Confined flow of ground water through a tunnel, which might be encountered in tunneling under the bottom of a sea or river, is numerically analyzed by a reductive finite element method formulated in our research. That is, the rate and potential distribution of the confined flow of ground water through an opening are obtained in connection with the permeability of rock masses, the thickness of covered ground, the location of impermeable bedrock, and other variables. In addition, flow through an opening in the ground with highly permeable masses and discharge of ground water through a tunnel in grouted masses are illustrated, and some useful results for the practical application of tunneling work are obtained.