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1.
The problem of the coseismic deformation of an earth model consisting of an elastic layer of uniform thickness overlying an
elastic half-space due to a very long tensile fault in the layer is solved analytically. Integral expressions for the surface
displacements are obtained for a vertical tensile fault and a horizontal tensile fault. The integrals involved are evaluated
approximately by using Sneddon’s method of replacing the integrand by a finite sum of exponential terms. Detailed numerical
results showing the variation of the displacements with epicentral distance for various source locations in the layer are
presented graphically. The displacement field in the layered half-space is compared with the corresponding field in a uniform
half-space to demonstrate the effect of the internal boundary. Relaxed rigidity method is used for computing the postseismic
deformation of an earth model consisting of an elastic layer of uniform thickness overlying a viscoelastic half-space. 相似文献
2.
As the fastest, lowest, flattest and amongst the most arid of continents, Australia preserves a unique geomorphic record of intraplate tectonic activity, evidencing at least three distinct modes of surface deformation since its rapid northward drift commenced around 43 million years ago. At long wavelengths (several 1000s km) systematic variations in the extent of Neogene marine inundation imply the continent has tilted north–down, southwest–up. At intermediate-wavelengths (several 100s km) several undulations of ~ 100–200 m amplitude have developed on the 1–10 myr timescale. At still shorter wavelengths (several 10s km), fault related motion has produced local relief at rates of up to ~ 100 m/myr over several million years. The long-wavelength, north–down tilting can be related to a dynamic topographic effect associated with Australia's northward drift from the geoid low, dynamic topography low now south of the continent to the geoid high, dynamic topography low centred above the south-east Asian and Melanesian subduction zones. The short wavelength, fault-related deformation is attributed in time to plate-wide increases in compressional stress levels as the result of distant plate boundary interactions and, in space, in part to variations in the thermal structure of the Australian lithosphere. At the intermediate wavelengths, transient, low amplitude undulations can be ascribed to either lithospheric buckling or the development of instabilities in the thermal boundary layer beneath the lithosphere. In the latter case, topographic asymmetries suggest the Australian lithosphere is moving north with respect to the mantle beneath, providing a unique attribution to the progressive alignment of seismic anisotropy and absolute plate motion observed near the base of the Australian lithosphere. 相似文献
3.
强夯加固地基的土体竖向位移计算方法研究 总被引：2，自引：0，他引：2
根据动力分析中应力边界与速度边界之间的关系,将应力边界时程转化为速度边界时程,提出计算土体竖向位移的新方法,并进行了简化和多角度对比性研究。在钱家欢加卸载模型应力和竖向位移计算的基础上,提出将正弦荷载形式和三角形荷载形式分别引入,推导出竖向位移的两种简化计算方法。两种方法概念清楚、物理意义明确,形式简单且相同,区别仅在于系数不同。工程实例表明,两种方法计算出的竖向位移均接近于实测位移,但正弦荷载形式下的位移计算方法更能反映实际情况。 相似文献
4.
弹性地基板的分析简化模型 总被引：1，自引：0，他引：1
将弹性半空间地基受任意竖向荷载作用下的静力位移积分变换解与弹性半空间地基上四边自由矩形板受任意竖向荷载作用的弯曲解析解相结合,建立了求解板下地基位移的方法。对一些算例进行大量数值计算分析,得出弹性半空间地基上四边自由矩形板板下地基水平位移和竖向位移的分布规律;并基于该位移分布规律,提出地基位移沿深度按一定的函数关系变化的假设,考虑板下地基水平位移,利用板地基系统的总势能最小原理,通过复杂的变分运算,得出弹性地基板的简化模型。在不考虑板下地基水平位移时,该模型退化成双参数地基模型,并给出了求解其上四边自由矩形板的近似边界条件。 相似文献
5.
A. P. S. Selvadurai 《国际地质力学数值与分析法杂志》1981,5(4):369-378
This paper examines the problem of the interaction between a loaded rigid circular foundation located at the surface of an isotropic elastic halfspace and an inclined concentrated anchor load which is located at a finite depth along the axis of symmetry. Such inclined loads can be induced by, for example, anchor regions supporting earth retaining structures. The loaded rigid circular foundation resting in smooth contact with the elastic soil mass experiences a displacement and a tilt due to the action of the inclined anchor load. The magnitude of the rotational settlement is evaluated in exact closed form. 相似文献
6.
简谐荷载作用下饱和土体中圆形衬砌隧道三维动力响应分析 总被引：2，自引：0，他引：2
研究了全空间饱和土体中圆形衬砌隧道在径向简谐点荷载作用下的三维动力响应,将衬砌用无限长圆柱壳来模拟,土体用Biot饱和多孔介质模型来模拟,引入两类势函数来表示土骨架的位移和孔隙水压力,并利用修正Bessel方程来求解各势函数,结合边界条件,得到频率-波数域内衬砌和土骨架位移、孔隙水压力的解答,最后进行Fourier逆变换得到时间-空间域内的响应。通过算例分析了荷载振动频率和土体渗透性对土体和衬砌位移响应及土体孔压的影响。结果表明,饱和土体和弹性土体的位移响应具有明显区别。随着荷载频率的增大,土体和隧道位移幅值减小,土体孔压幅值增大;随着土体渗透性增大,土体位移及孔压幅值减小。 相似文献
7.
The solution of static elastic deformation of a homogeneous, orthotropic elastic uniform half-space with rigid boundary due to a non-uniform slip along a vertical strike-slip fault of infinite length and finite width has been studied. The results obtained here are the generalisation of the results for an isotropic medium having rigid boundary in the sense that medium of the present work is orthotropic with rigid boundary which is more realistic than isotropic and the results for an isotropic case can be derived from our results. The variations of displacement with distance from the fault due to various slip profiles have been studied to examine the effect of anisotropy on the deformation. Numerically it has been found that for parabolic slip profile, the displacement in magnitude for isotropic elastic medium is greater than that for an orthotropic elastic half-space, but, in case of linear slip, the displacements in magnitude for an orthotropic medium is greater than that for the isotropic medium. 相似文献
8.
We rederive and present the complete closed-form solutions of the displacements and stresses subjected to a point load in a transversely isotropic elastic half-space. The half-space is bounded by a horizontal surface, and the plane of transverse isotropy of the medium is parallel to the horizontal surface. The solutions are obtained by superposing the solutions of two infinite spaces, one acting a point load in its interior and the other being free loading. The Fourier and Hankel transforms in a cylindrical co-ordinate system are employed for deriving the analytical solutions. These solutions are identical with the Mindlin and Boussinesq solutions if the half-space is homogeneous, linear elastic, and isotropic. Also, the Lekhnitskii solution for a transversely isotropic half-space subjected to a vertical point load on its horizontal surface is one of these solutions. Furthermore, an illustrative example is given to show the effect of degree of rock anisotropy on the vertical surface displacement and vertical stress that are induced by a single vertical concentrated force acting on the surface. The results indicate that the displacement and stress accounted for rock anisotropy are quite different for the displacement and stress calculated from isotropic solutions. © 1998 John Wiley & Sons, Ltd. 相似文献
9.
Ghadi Younis 《Arabian Journal of Geosciences》2015,8(10):8681-8685
In Geodesy, the heights of points are normally orthometric heights measured above the geoid (an equipotential surface created by the earth masses and rotation which approximately coincides with the mean sea level) or the normal heights. It is necessary to transform the GNSS/GPS measured ellipsoidal heights (h) to classical physical heights (orthometric H/Normal H). The total gravity potential of the earth (W) is the summation of two components; gravitational potential (V) by earth masses and the centrifugal potential (Ω). The centrifugal potential is directly calculated, while the gravitational potential (V) needs to be modeled globally or locally using given measurements. The global models of the earth gravitational potential/gravity models (or so-called geoid models) are mostly given using spherical harmonics (SH). A modified approach of SH was defined to fit the use of SH for regional gravity/potential modeling called spherical cap harmonics (SCH). Due to the numerical difficulties of SCH, a simplified approach of SCH is selected to be used for a combined modeling of the earth potential using a variety of observations. This approach is called the Adjusted Spherical Cap harmonics. 相似文献
10.
Effects of mantle upwelling in a compressional setting: the Atlas Mountains of Morocco 总被引：1，自引：0，他引：1
Antonio Teixell Puy Ayarza Hermann Zeyen Manel Fernàndez María-Luisa Arboleya 《地学学报》2005,17(5):456-461
We discuss the implications of a lithospheric model of the Moroccan Atlas Mountains based on topography, heat flow, gravity and geoid anomalies, taking into account the regional geology. The NW African cratonic lithosphere, some 160–180 km thick, thins to c. 80 km beneath the Atlas fold-thrust belts, in contrast with the shortening regime prevailing there since the early Cenozoic. This fact explains several geological and geophysical features as high topography with modest tectonic shortening, the occurrence of alkaline magmatism contemporaneous to compression, the absence of large crustal roots to support elevation, the scarce development of foreland basins, and a marked geoid high. The modelled lithosphere thinning is related to a thermal upwelling constrained between the Iberia–Africa convergent plate boundary and the Saharan craton. 相似文献
11.
Detachment of the deeper part of subducted lithosphere causes changes in a subduction zone system which may be observed on the Earth's surface. Constraints on the expected magnitudes of these surface effects can aid in the interpretation of geological observations near convergent plate margins where detachment is expected. In this study, we quantify surface deformation caused by detachment of subducted lithosphere. We determine the range of displacement magnitudes which can be associated with slab detachment using numerical models. The lithospheric plates in our models have an effective elastic thickness, which provides an upper bound for rapid processes, like slab detachment, to the surface deformation of lithosphere with a more realistic rheology. The surface topography which develops during subduction is compared with the topography shortly after detachment is imposed. Subduction with a non-migrating trench system followed by detachment leads to a maximum surface uplift of 2–6 km, while this may be higher for the case of roll-back preceding detachment. In the latter situation, the back-arc basin may experience a phase of compression after detachment. Within the context of our elastic model, the surface uplift resulting from slab detachment is sensitive to the depth of detachment, a change in friction on the subduction fault during detachment and viscous stresses generated by sinking of the detached part of the slab. Overall, surface uplift of these magnitudes is not diagnostic of slab detachment since variations during ongoing subduction may result in similar vertical surface displacements. 相似文献
12.
DEEP GEODYNAMICS OF THE HIMALAYA OROGENYRFBR( grant 990 56 56 38) 相似文献
13.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》2000,25(4):343-353
Details of the Earth's geoid and gravity fields are summarized and examined. A set of 9274 centerpoints of 5 ° cubes (referred to as bloblets) represents subducted slab locations. This set, developed from reconstructed plate history, was provided by the first author of Lithgow-Berttelloni et. al. [1998] and is the best available estimate of locations of subduction material in the Earth's mantle. Two global mass solutions offered here utilize 1) only those bloblets in the outer 800 km, and 2) only those bloblets in the outer 1400 km. Since each bloblet location represents the center of a 5-degree cube [a larger volume than appropriate for a fragment of subducted lithosphere] it was necessary in the 800 km depth limit model to reduce their density to 0.004 grams/cc, and by increasing bloblet density six times at 797.5 km depth to simulate the piling up of slab material beneath the 670 km boundary. The 1400 km depth limit model [commensurate with evidence of slab penetration into the lower mantle from seismic tomography] required estimating densities for the bloblets at nine different mantle depths. An additional four point-masses at 3000 km depth (to simulate CMB topography, unrelated to dynamic topography) completes the mass models. Both these models show reasonable agreement to patterns and magnitudes for degrees 2–10, 3–10, 4–10, 2–3, 3, and 2 geoid fields with both geometric and hydrostatic flattening. These models support an assessment that topography at the core mantle boundary (CMB) may be produced by processes within the core rather than from within the mantle. Possible causes for the CMB topography are discussed. 相似文献
14.
幔羽现象与地震电磁流体效应的可能联系——电磁流体效应和平面电流模型 总被引：4，自引：1，他引：4
综合分析了 2 0世纪 70年代以来发生在中国的 14个强震前地磁和地下流体参量动态图像的时空演化特征 ,发现强震前这些参量均呈现十分明显的异常图形。这些图像十分复杂 ,且随时间不断变化 ,并与孕震过程有某种时空规律性联系。 90年代地学家通过地震资料分析发现了幔羽现象。笔者设想核幔边界的幔羽磁流体物质上涌是地震电磁流体效应的一种可能成因。幔羽中的流体物质螺旋上涌至地壳的底部 ,并形成“蘑菇云”。流体在地壳中扩展或挤压 ,形成异常电流 ,可将其看作在孕震区地下 10 2 0km深处有一等效平面电流。再考虑到近地表的电磁环境———电离层电流体系的局部异常 ,计算了一个地下和电离层组成的等效平面电流模型在地面产生的磁场分布 ,结果与强震前地球磁场的零等变型异常动态图像较吻合。 相似文献
15.
Numerical integration required during Fourier integral analysis is discussed. For the case of a long and prismatic elastic medium subject to three-dimensional loads applied at the surface (e.g. live load response of buried structures), the complexity of inverse integrals depends on the relative magnitude of the load width and the distance from the load in the longitudinal direction, as well as the longitudinal spacing of the loads. The inverse integrand of the applied surface loading is more difficult to evaluate compared to those for stresses and displacements. Selection of integration schemes based on successful inversion of the applied load provides accurate solutions of stress and displacement throughout the elastic body. The use of superposition when considering complex loading cases is beneficial. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
16.
Most analytical or semi‐analytical solutions of the problem of load‐settlement response of axially loaded piles are based on the assumption of zero radial displacement. These solutions also are only applicable to piles embedded in either a homogeneous or a Gibson soil deposit. In reality, soil deposits consist of multiple soil layers with different properties, and displacements in the radial direction within the soil deposit are not zero when the pile is loaded axially. In this paper, we present a load‐settlement analysis applicable to a pile with circular cross section installed in multilayered elastic soil that accounts for both vertical and radial soil displacements. The analysis follows from the solution of the differential equations governing the displacements of the pile–soil system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. We compare the results from the present analysis with those of an analytical solution that considers only vertical soil displacements. The analysis presented in this paper also provides useful insights into the displacement and strain fields around axially loaded piles. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
17.
Spatial pattern analysis of marine terrace elevations from 40–30 thous. years BP was used to reconstruct sea level/geoid surface
and geoid parameters during that time. The polar flattening of geodetic ellipsoid was lower than its present value (1/298.81
and 1/298.26) respectively because of glacial-induced mass redistribution. Increase in polar stress occurred during the last
30 thous. years was possibly driven by pertubation brought to the gravitational field by disintegration of polar ice sheets
in the Northern hemisphere. But the polar flattening value becomes only half-restored during the last deglacial hemicycle.
So repetitive glacial advances during Pleistocene acted as a global “pump” for uncondensed zones at the upper/lower mantle
boundary. Dissipation of tidal energy is an order of magnitude less intensive in its Earth's rotation effect.
A contribution to the International Geological Correlation Programme Project JGCP — 274 “Coastal Evolution in the Quaternary”. 相似文献
18.
The complete gravity data set from France and part of the neighboring countries has been analyzed to compute the topography of the Moho undulations. This work is based on an improved filtering technique and an appropriate assumed density contrast between the crust and the upper mantle. Comparison with deep seismic refraction data reveals that this relief map expresses the continuity and geometry of the Moho undulations better than the sparsely distributed seismic refraction data in France. This gravity Moho map, though may not give absolute depths at places, provides a far better correlation with surface geology than the result from other geophysical techniques. Four domains have been recognized: (a) the Alpine domain where all the Moho undulations are concentric with the Alps; (b) the Armorican domain in which all the undulations are north-west/south-east oriented; (c) the Pyrenean domain, in which the undulations are parallel with the Mountain chain; and (d) the Massif Central Domain which does not show clear structural orientation because of the influence of the strong heat flow located at the lower crust/upper mantle interface. Study of the topography and of the superficial structures associated with these undulations reveals that the undulations delineated in the Alpine Domain result from the Tertiary compression which shaped the Alps. The Armorican Domain was first created during the Lower to Middle Cretaceous opening of the Bay of Biscay. It is now slightly affected by the Tertiary to Quaternary closure of this Bay. The Pyrenean Domain was successively shaped by the Lower Cretaceous oblique opening of the Bay of Biscay and by the Upper Cretaceous to Eocene northward displacement of Spain. Comparison between the Moho undulations map and the stress map of France reveals that most of the undulations are perpendicular to the actual shortening directions. This observation suggests that the Mesozoic, Cenozoic and Quaternary stress directions were roughly the same. Massif Central is characterized by the convergence of these three sets of undulations. Its Post-Oligocene uplift was probably the result of the converging stresses recognized in the three surrounding domains. When the Moho undulations and the topography are compared, two types of periodic crustal instabilities can be recognized. One corresponds to the buckling of the crust developed under compression, the other to boudinage which was associated with extension. Both phenomena show a typical wavelength of 200–250 km which is in agreement with the results of the actual physical and numerical modeling currently available. 相似文献
19.
2008年5月12日14时28分04秒,四川省汶川县发生MS8.0大地震。发震断裂为龙门山断裂带,地震地表破裂带分布在北川-映秀断裂上的映秀-石坎子段和江油-灌县断裂上的磁峰-睢水段。平武县平通镇地表破裂现象典型,在T1和T2阶地上形成了地震断坎和裂缝。应用高精度GPSRTK技术对平通镇地震断坎及两侧作详细的地形测量,并测量了线性显著的路面中线和鱼塘西边壁。在室内生成高分辨率DEM与大比例尺地形剖面图,量取同震垂直与水平位移,并估算压缩缩短量和断层产状。结果显示汶川8.0级地震在平通镇形成的同震垂直位移为3.0±0.1m,右旋水平位移为4.0±0.2m,压缩缩短量为2.5m,断层产状为NE40°/NW∠50°。平通镇的同震右旋位移与本次地震的最大右旋位移相近,而逆冲垂直位移有所降低。 相似文献
20.
基于库仑土压力理论的假设,主动土压力是由墙后填土在极限平衡状态下出现的滑动体产生,从墙后滑动体整体静力平衡方程出发,推导出坡面起伏且有不均匀超载、倾斜墙背、黏性填土等一般情况下的主动土压力泛函极值的等周模型。在该基础上,引入拉格朗日乘子,将主动土压力问题转化为确定含有两个函数自变量的泛函极值问题。依据泛函取极值时必须满足的欧拉方程,得到了线性的滑面函数和沿滑面线性分布的法向应力函数。结合边界条件和横截条件,主动土压力泛函极值问题进一步转化为单个未知量的一维方程问题。通过算例,土压力计算结果与库仑土压力理论解完全一致,但土压力作用点在墙体的相对位置却并非总是作用在墙高的1/3 处。通过算例进一步表明,坡面的起伏和坡面超载的不均匀性对主动土压力大小和作用点位置有显著的影响。 相似文献