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251.
Zhong Jimao 《中国地震研究》2006,20(3):339-350
INTRODUCTIONThe introductiontothe damage variable was made originally by Kachanov (1958) and Rabotnov(1963) .As a factor of deterioration in material or rock,damage develops with the changing of loadand environment . The damage variable describes the characteristics of material in the stage frommicrofissure generationto macrofracture formation.Grady and Kipp (1980) loaded oil shale at a constant strainrate andits damage degreeincreasedrapidly. Whenthe load reachedits utmost ,collapse occ… 相似文献
252.
用矩张量反演的方法,通过对1982年10月19日河北卢龙MS6.1地震的余震序列的震源机制求解,认为卢龙盆地的主压应力轴方位角为N74deg;E,近东西向;而盆地的北边变为N43deg;E;在盆地中心有些部位主压应力轴转为北西方向,与盆地周边的主压应力轴方位几乎垂直. 这说明在卢龙地震中构造的不同部位地壳应力方位很不一致,反映出卢龙地区构造活动的复杂性. 一方面,由于卢龙位处中国大陆东部,受到来自东部的日本海盆地在太平洋板块驱动力作用下的挤压;另一方面,卢龙又夹持在燕山地块与华北板块之间,因而受块体边界的限制也是很明显的. 相似文献
253.
Quantifying Damage, Saturation and Anisotropy in Cracked Rocks by Inverting Elastic Wave Velocities 总被引:1,自引:0,他引:1
Alexandre Schubnel Philip M. Benson Ben D. Thompson Jim F. Hazzard R. Paul Young 《Pure and Applied Geophysics》2006,163(5-6):947-973
Crack damage results in a decrease of elastic wave velocities and in the development of anisotropy. Using non-interactive
crack effective medium theory as a fundamental tool, we calculate dry and wet elastic properties of cracked rocks in terms
of a crack density tensor, average crack aspect ratio and mean crack fabric orientation from the solid grains and fluid elastic
properties. Using this same tool, we show that both the anisotropy and shear-wave splitting of elastic waves can be derived.
Two simple crack distributions are considered for which the predicted anisotropy depends strongly on the saturation, reaching
up to 60% in the dry case. Comparison with experimental data on two granites, a basalt and a marble, shows that the range
of validity of the non-interactive effective medium theory model extends to a total crack density of approximately 0.5, considering
symmetries up to orthorhombic. In the isotropic case, Kachanov's (1994) non-interactive effective medium model was used in
order to invert elastic wave velocities and infer both crack density and aspect ratio evolutions. Inversions are stable and
give coherent results in terms of crack density and aperture evolution. Crack density variations can be interpreted in terms
of crack growth and/or changes of the crack surface contact areas as cracks are being closed or opened respectively. More
importantly, the recovered evolution of aspect ratio shows an exponentially decreasing aspect ratio (and therefore aperture)
with pressure, which has broader geophysical implications, in particular on fluid flow. The recovered evolution of aspect
ratio is also consistent with current mechanical theories of crack closure. In the anisotropic cases—both transverse isotropic
and orthorhombic symmetries were considered—anisotropy and saturation patterns were well reproduced by the modelling, and
mean crack fabric orientations we recovered are consistent with in situ geophysical imaging.
Our results point out that: (1) It is possible to predict damage, anisotropy and saturation in terms of a crack density tensor
and mean crack aspect ratio and orientation; (2) using well constrained wave velocity data, it is possible to extrapolate
the contemporaneous evolution of crack density, anisotropy and saturation using wave velocity inversion as a tool; 3) using
such an inversion tool opens the door in linking elastic properties, variations to permeability. 相似文献
254.
InversionofsourceprocesandrelatedstudiesoftheTaiwanStraitearthquakeus-inggeneticalgorithmHAI-JUNWANG1)(王海军)BANG-HUILIN1)(林邦慧... 相似文献
255.
支护结构位移对侧土压力影响的计算分析 总被引:1,自引:0,他引:1
针对传统土压力理论在应用中的不足,提出一种基于弹性地基理论的土压力计算方法,可充分考虑墙体对土压力重分布的影响。 相似文献
256.
Effects of galvanic distortion on magnetotelluric data over a three-dimensional regional structure 总被引:2,自引:0,他引:2
Although the galvanic distortion due to local, near-surface inhomogeneities is frequency-independent, its effect on the magnetotelluric data becomes, in a 3-D structure, frequency-dependent. Therefore, both the apparent resistivity and the phase responses are disturbed, and a correction should be carried out prior to the 3-D interpretation in order to retrieve the 3-D regional impedance tensor. In many cases, the structure is 2-D for depths corresponding to a first range of periods and 3-D for longer periods (called 2-D/3-D). For these cases, a simple method which allows us to retrieve the 3-D regional impedance tensor (except the static shift) is presented. The method proposed uses the Groom & Bailey decomposition of the distortion matrix for the short periods. Three examples are presented: two using synthetic data and one employing real data. These examples show the effect of the galvanic distortion over a regional 2-D/3-D model and the retrieval of the regional transfer functions from the distorted ones. 相似文献
257.
基于Maxwell和Kelvin流变模型,以延续时间与松弛期的比值,即松弛数,作为衡量指标,对地壳、上地幔不同层次的变形属性进行了判别。结果表明,除软流圈地幔主要为粘性流动外,其上各层的情况是:在漫长的地质过程中,不仅岩石圈地幔和下地壳属于粘性,上地壳也有可能处于粘性流动状态;在延续数十年的情况下,上地壳以及岩石圈地幔都可能呈弹性状态;延续时间介乎二者,通常上地壳为弹性,下地壳和岩石圈地幔为粘性或滞弹粘性。此外,还结合变形属性的判别,就岩石圈地幔的流动和板内的驱动力远程传递等问题进行了讨论 相似文献
258.
259.
断层地震孕震的椭圆形区域及其前兆规律 总被引:2,自引:2,他引:2
首先运用岩石介质的损伤本构关系式和断层地震的简单力学模型,讨论了断层和围岩介质系统的相互作用及其失稳过程,通过差分计算,得到了与地震变形和声发射等有关的前兆序列曲线,然后根据实际断层带滑移与错动的分布规律,通过计算机模拟出断层地震的椭圆形孕震区并此解释了P波初动分布规律。 相似文献
260.
Ari Ben-Menahem 《Pure and Applied Geophysics》1988,128(1-2):133-146
A nonstochastic and noniterative theory of vector scattering in inhomogeneous media is presented. The elastodynamic vector wave-equation for 3D inhomogeneous media is solved for a weak heterogeneity at the high-frequency region. It is shown that there exists a forward scattered field which decays slowly along the source-receiver path. Its rate of attenuation depends on the azimuth of the path relative to the direction of the inhomogeneity, but is independent of frequency. The Green's tensor for the above regime is derived in closed form and leads to the quantification of fields of dipolar sources in weak inhomogeneous media. The inhomogeneity at the source creates a source-induced scattering (in addition to path-scattering) having a radiation-pattern that bears the signature of the source. The availability of the analytic Green's tensor, in conjunction with the Huygens-Kirchhoff-Helmholtz formalism, opens new ways to calculate the scattered fields due to various structural inhomogeneities applicable to exploration and earthquake seismology. The theoretical results of this study point to the conclusion that the scalar wave approximation may not always be valid for the propagation of seismic waves in the earth's lithosphere. 相似文献