无限饱水孔隙弹性空间中由运动源所产生的位移场

基于Ｂｉｏｔ的饱和孔隙弹性介质的运动方程和利用复变函数方法，本文研究了无限饱水孔隙弹性空间中由常速运动源所产生的位移场。考虑了两种类型源：ａ．沿无限空间水平轴运动的斜向集中力源；ｂ．运动双力偶源。关于力源的运动速度，考虑了４种情形：ａ．力源的运动速度Ｕ小于饱水孔隙弹性介质的三种体波速度一亚音速情形；ｂ．速度Ｕ小于介质的第一纵波过度和横波速度，但大于第二纵波速度─—弱跨音速情形；ｃ．速度Ｕ小于第一纵波速度，但大于横波速度和第二级波速度─—强跨音速情形；ｄ．速度Ｕ大于介质的所有三种体波速度─—超音速情形。结果表明，在跨音达和超音速情形里，解呈现出与力源相联系的平面冲击波特征，位移出现了相应的跳跃。     

各向异性ATI介质剪切位错源地震矩张量

考虑震源区为各向异性ATI介质情形下,给出了剪切位错源地震矩张量解析表达式并模拟了震源区各向异性对双力偶分量(DC)、补偿线性偶极子分量(CLVD)和各向同性分量(ISO)的影响,结果表明,即使剪切位错源仍能产生非双力偶各向同性分量,其导致沿着ATI介质对称轴方向体积变化;当断层面位于ATI介质对称平面或者震源区为各向...     

动态破裂远场辐射的单力偶分量

重新审核了地震学文献中的两条基本原理,即远场弹性位移与动态断层面上的滑动速度成正比,以及地震断层上的平面动态滑动与双力偶体力等效等两条基本原理。我们指出,如果断裂发生于具有一定厚度的断层上,并且向前扩展的裂纹端部附近存在强度弱化区的话,则在与其等效的体力中会有一个附加的单力偶项,且在远场位移中也会有一个与向前扩展的强度弱化区内的应力降随时间增加的变化率成正比的附加项。我们还指出,与单力偶等效的体力并不违背牛顿力学原理,因为单力偶转矩为断层区内的旋转所平衡;于是,裂纹便辐射出扭转波与旋转形变场。     

各向异性ATI介质剪切位错点源P波远场辐射

假设震源区为ATI介质,传播介质为全空间各向同性介质情况下,给出了剪切位错源P波远场辐射解析表达式,讨论了震源区各向异性对远场P波振幅和震源球的影响。结果表明,震源区裂隙密度,裂隙方位等参数的动态变化导致P波远场辐射花样也随之动态变化,同时也会造成非双力偶百分含量的动态变化。研究认为,在井中对中小地震的非双力偶机制进行...     

断层活动的重力效应

本文对介质变形造成的重力变化作了定量分析,通过质点位移法(拉格朗日法)导出了介质位移场和由它产生的附加重力场之间的积分关系式.应用已有的弹性和粘弹性半空间任意倾角断层位错的位移表达式,本文通过三维空间数值积分,计算了弹性介质和广义开尔文介质中断层不同的运动方式所产生的地表附加重力场,以及介质流变性导致的重力随时间的变化趋势.参考唐山地震前沧东断裂的活动和震时断层错动,计算了震前震后相应的重力变化,其结果与实测重力资料有一定程度的符合.     

断层活动的重力效应ht

本文对介质变形造成的重力变化作了定量分析, 通过质点位移法(拉格朗日法)导出了介质位移场和由它产生的附加重力场之间的积分关系式.应用已有的弹性和粘弹性半空间任意倾角断层位错的位移表达式, 本文通过三维空间数值积分, 计算了弹性介质和广义开尔文介质中断层不同的运动方式所产生的地表附加重力场, 以及介质流变性导致的重力随时间的变化趋势.参考唐山地震前沧东断裂的活动和震时断层错动, 计算了震前震后相应的重力变化, 其结果与实测重力资料有一定程度的符合.      

各向异性ATI介质地震矩张量理论研究

引言地震矩张量描述了地震点源的基本特征,其内容涉及到各类震源(包括剪切位错震源、张裂震源和体积震源)的力学机制、震源辐射、地应力场、震源运动学和强地面运动等地震学中的重要课题。一般认为,浅源构造地震是因断层面间的快速纯剪切错动而辐射地震波,造成在地表的振动,传统上该解释被称为双力偶机制。但实际地震观测和地震矩张量反演结果     

1929年大浅滩地震的复杂双力偶震源机制

1929年大浅滩地震(M_s=7.2)是发生在加拿大的最大和最致命的地震之一。这次地震引起的海啸和海底滑坡造成大量的死亡和破坏。曾经认为(Hasegawa and Kanamori,1987),单力机制(滑坡)比双力偶机制更符合观测资料,因之曾认为这个事件不是地震。但是个别的研究只考虑了4个双力偶解并且留下了许多不能回答的问题,特别是与震源时间函数和沉积物体积有关的问题。本文用了大量的地震图来核查全范围的双力偶解,以便进一步确定这次事件的性质。通过波形正演和反演两种方法,表明这是一次有复杂震源机制的地震事件。第1个也是最大约子事件是沿北西走向断层面发生的走滑双力偶事件,后面两个子事件可能是沿北东走向断层面上的走滑双力偶机制,但也不能完全排除其他类型的机制。第1个子事件有约束较好、为20±2km的震源深度,另两个子事件深度似乎也为20km,但精度为±5km。这些震源深度结果也说明这次事件不是滑坡。子事件地震矩之和相当于一个M_w=7.2±0.3的地震,和长周期资料的矩心矩张量(CMT)方法得到的M_w=7.1±0.1的地震的矩很一致,也和直接从地震图上计算的M_s=7.2(±0.3),m_b=7.1(±0.2)的矩差不多。用双力偶机制模拟海底位移结果表明,海啸是滑坡产生的,不是地震直接引起的。     

通用流变介质中地震波的传播特性

本文采用一种通用流变介质模型,从理论上详细讨论了地震波在该介质中的传播特性,并对流变介质中准静态位错产生的位移场及地壳介质品质因子Q作了讨论。     

非双力偶地震：理论（一）

历史上多数定量地震学的分析是以地震由剪切断裂引起这一假设为根据的,这样其各向同性介质中的等效力系是一对无扭矩的力偶。然而,现在高质量和高覆盖的观测资料使人们能分辩出许多地民双力有偏离,发现一些地震,特别是在火山地区和地热区域的地震,有很强的非双力偶机制。了解非双力偶地震对于仔细研究断裂过程和辨别在某些地震中明显发生的非剪切断裂过程都是重要的。本文了等效力系的“矩阵张量”展开理论,并分析了多个非双力     

两相饱和介质半无限空间位错位移场

弹性位错理论是研究地震震源正演和反演的重要工具之一. 单相介质位错理论求得的地面变形场是稳定的、不变的，而实际地震后的地面变形场是变化的. 本文利用集中力作用下无限空间中两相饱和介质Green函数的柱函数表达式，通过弹性运动方程积分解的Helmholtz方程的Hansen矢量变换，再叠加自由表面影响场的方法求得两相饱和介质半无限空间位错位移场. 本文结果结合Nur的DD模式，在进水排水的假说下能解释地震后地面变形场的变化.     

The source vector and static displacement field by elastic dislocation on the two-phase saturated medium

IntroductionSince Steketee introduced the elastic dislocation theory into geophysics in 1958, it has become an important part of seismology. Because the fracture of fault can be treated as a displacement bound, the elastic displacement field (forward problem) can be studied by the static elastic dislocation theory under some given condition. Vice versa, if the static displacement field is known, the cause (inverse problem) can be inferred by the dislocation theory. In the last 40 years, many …     

多层弹性半空间中的地震波（二）

一、引言 地震面波的频散性质、地震波辐射的方向性等特性已经广泛地用于地壳和上地幔结构以及震源机制的研究中,并且取得了许多有用的成果.研究地震波如何从震源辐射出来、如何在实际介质中传播和衰减的这一问题,对于利用地震波确定地壳和上地幔结构以及震源的参数,是很有必要的.关于这一问题的研究,已经作过许多工作。已往的工作中,为了分析方便,往往采用简单的地壳-上地幔模型或简单的震源模型,或两者都相     

地震体波的动力学辐射理论

本文利用弹性介质的动力学关系建立了地震体波辐射动力学理论，并给出了地震远场体波位移的多级展开式，然后，对零级辐射及一级辐射做了重点讨论，作为地震辐射场源的内外激发源具有明显的物理意义。     

Response of a semi-infinite elastic solid to an arbitrary torque along the axis

Summary The response of an otherwise stress-free elastic half space to an arbitrarily distributed static torque along the axis of symmetry is obtained. As an example, numerical results are found for the stress and displacement fields due to the special case of a concentrated torque acting at a finite distance from the free surface.     

Quasi-static Planar Deformation in a Medium Composed of Elastic and Thermoelastic Solid Half Spaces Due to Seismic Sources in an Elastic Solid

A two-dimensional problem of quasi static deformation of a medium consisting of an elastic half space in welded contact with thermoelastic half space, caused due to seismic sources, is studied. Source is considered to be in the elastic half space. The basic equations, governed by the coupled theory of thermoelasticity, are used to model for thermoelastic half space. The analytical expressions for displacements, strain and stresses in the two half spaces are obtained first for line source and then for dip slip fault. The results for two particular cases, adiabatic conditions and isothermal conditions, are also obtained. Numerical results for displacements, stresses and temperature distribution have also been computed and are shown.     

Static displacement fields due to a seismic source in a nonhomogeneous (dimorphic) medium. Geophysical applications

A new method for finding static displacement fields due to seismic sources (forces or dislocations) in a nonhomogeneous medium (called “dimorphic”) is presented. Previously known results can be easily calculated, as well as new results for sources located at the interface between two media with different elastic properties. The ratio of displacement magnitudes in homogeneous and dimorphic media, which can be as great as 15%, is calculated. Consequences for the seismic moment and some other geophysical applications are discussed.     

SH waves in a semi-infinite elastic space due to torsional disturbance

Summary The paper concerns the finding of displacement in a semi-infinite elastic space due to torsional disturbance produced by an expanding source. A formal solution has been derived by the integral transform technique and the modified Cagniard method in two different cases, viz. velocity of expansion is less than or greater than the velocity of shear waves in the medium.     

Transient scattering of elastic waves by dipping layers of arbitrary shape. Part 2: Plane strain model

Scattering of elastic waves by dipping layers of arbitrary shape embedded within an elastic half-space is investigated for a plane strain model by using a boundary method. Unknown scattered waves are expressed in the frequency domain in terms of wave functions which satisfy the equations of motion and appropriate radiation conditions at infinity. The steady state displacement field is evaluated throughout the elastic medium for different incident waves so that the continuity conditions along the interfaces between the layers and the traction-free conditions along the surface of the half-space are satisfied in the least-squares sense. Transient response is constructed from the steady state one through the Fourier synthesis. The results presented show that scattering of waves by dipping layers may cause locally very large amplification of surface ground motion. This amplification depends upon the type and frequency of the incident wave, impedance contrast between the layers, component of displacement which is being observed, location of the observation station and the geometry of the subsurface irregularity. These results are in agreement with recent experimental observations.