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11.
波动特征研究对各向异性介质的弹性参数反演,速度反演、NMO,DMO、时间域的偏移以及地震资料的精确解释有着重要意义.本文由Christoffel方程出发推导出二维VTI介质中XOZ对称平面内弹性波相速度与各向异性参数的关系式以及慢度面的计算式并通过理论模型分析得出以下结论：1)ε值决定了P波的水平相速度的大小,反映了P波水平传播的相速度与垂直传播的相速度的差异;δ值决定了P波垂直方向附近相速度的各向异性程度的大小.2)VTI各向异性介质中纵波偏振方向不再与慢度面是平行而是有一定的夹角,且SV波的慢度面不再完全与偏振方向垂直的.3)准SH 波的波慢度面呈椭圆,准P波与准SV波慢度面为不规则椭圆. 相似文献
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In the monitoring of earthquakes and nuclear explosions using a sparse worldwide network of seismic stations, it is frequently
necessary to make reliable location estimates using a single seismic array. It is also desirable to screen out routine industrial
explosions automatically in order that analyst resources are not wasted upon detections which can, with a high level of confidence,
be associated with such a source. The Kovdor mine on the Kola Peninsula of NW Russia is the site of frequent industrial blasts
which are well recorded by the ARCES regional seismic array at a distance of approximately 300 km. We describe here an automatic
procedure for identifying signals which are likely to result from blasts at the Kovdor mine and, wherever possible, for obtaining
single array locations for such events. Carefully calibrated processing parameters were chosen using measurements from confirmed
events at the mine over a one-year period for which the operators supplied Ground Truth information. Phase arrival times are
estimated using an autoregressive method and slowness and azimuth are estimated using broadband f{-}k analysis in fixed frequency bands and time-windows fixed relative to the initial P-onset time. We demonstrate the improvement
to slowness estimates resulting from the use of fixed frequency bands. Events can be located using a single array if, in addition
to the P-phase, at least one secondary phase is found with both an acceptable slowness estimate and valid onset-time estimate.
We evaluate the on-line system over a twelve month period; every event known to have occured at the mine is detected by the
process and 32 out of 53 confirmed events were located automatically. The remaining events were classified as “very likely”
Kovdor events and were subsequently located by an analyst. The false alarm rate is low; only 84 very likely Kovdor events
were identified during the whole of 2003 and none of these were subsequently located at a large distance from the mine. The
location accuracy achieved automatically by the single-array process is remarkably good, and is comparable to that obtained
interactively by an experienced analyst using two-array observations. The greatest problem encountered in the single array
location procedure is the difficulty in determining arrival times for secondary phases, given the weak Sn phase and the complexity
of the P-coda. The method described here could be applied to a wide range of locations and sources for which the monitoring
of seismic activity is desirable. The effectiveness will depend upon the distance between source and receiver, the nature
of the seismic sources and the level of regional seismicity. 相似文献
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In viscoelastic media, the slowness vector p of plane waves is complex-valued, p = P + iA. The real-valued vectors P and A are usually called the propagation and the attenuation vector, repectively. For P and A nonparallel, the plane wave is called inhomogeneousThree basic approaches to the determination of the slowness vector of an inhomogeneous plane wave propagating in a homogeneous viscoelastic anisotropic medium are discussed. They differ in the specification of the mathematical form of the slowness vector p. We speak of directional specification, componental specification and mixed specification of the slowness vector. Individual specifications lead to the eigenvalue problems for 3 × 3 or 6 × 6 complex-valued matrices.In the directional specification of the slowness vector, the real-valued unit vectors N and M in the direction of P and A are assumed to be known. This has been the most common specification of the slowness vector used in the seismological literature. In the componental specification, the real-valued unit vectors N and M are not known in advance. Instead, the complex-valued vactorial component p
of slowness vector p into an arbitrary plane with unit normal n is assumed to be known. Finally, the mixed specification is a special case of the componental specification with p
purely imaginary. In the mixed specification, plane represents the plane of constant phase, so that N = ±n. Consequently, unit vector N is known, similarly as in the directional specification. Instead of unit vector M, however, the vectorial component d of the attenuation vector in the plane of constant phase is known.The simplest, most straightforward and transparent algorithms to determine the phase velocities and slowness vectors of inhomogeneous plane waves propagating in viscoelastic anisotropic media are obtained, if the mixed specification of the slowness vector is used. These algorithms are based on the solution of a conventional eigenvalue problem for 6 × 6 complex-valued matrices. The derived equations are quite general and universal. They can be used both for homogeneous and inhomogeneous plane waves, propagating in elastic or viscoelastic, isotropic or anisotropic media. Contrary to the mixed specififcation, the directional specification can hardly be used to determine the slowness vector of inhomogeneous plane waves propagating in viscoelastic anisotropic media. Although the procedure is based on 3 × 3 complex-valued matrices, it yields a cumbersome system of two coupled equations. 相似文献
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基于常规测井数据计算储层岩石力学参数——以鄂尔多斯盆地上古生界为例 总被引：2，自引：1，他引：1
泊松比及杨氏模量等岩石力学参数是盆地构造应力场模拟、油气田钻完井及储层压裂改造设计的基础参数。在岩石力学实验研究及纵、横声波时差关系研究的基础上,针对鄂尔多斯盆地上古生界储层确定了基于常规测井资料计算横波时差关系式的待定系数A、B、C,通过最小二乘法拟合的3个待定系数值分别为2.74、25.45、-370.16,基于待定系数计算公式求取的横波时差与实测横波时差具有较好的一致性。通过该方法计算出研究区上古生界储层杨氏模量在35593~37997 MPa之间,泊松比在0.21~0.25之间。研究区岩石力学参数计算公式的确定及岩石力学参数计算为鄂尔多斯盆地气田勘探开发提供了数据基础。 相似文献
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弹性波层析成像技术简称“弹性波CT扫描”,是在不损坏物体的前提下,利用弹性波射线穿透地层时,其走时及振幅与地层内部的某些物理参数存在线性积分关系的这一关键特征,反演地层内部三维速度结构或衰减特性的方法。本文基于弹性波CT技术,通过孔间岩体慢度反演,综合钻孔编录及工程现场情况,对承德市半壁山危岩体中破裂发育情况进行综合解译,测定岩体破裂发育的位置和规模。实践证明,采用弹性波CT方法探测得到的破裂位置与钻孔揭露的情况吻合,为危岩体的整治提供了依据。 相似文献
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利用层析成像的基本原理对地质异常体进行速度层析成像正、反演研究,计算结果可以确定出地质模型中速度异常体的大小、位置和慢度值等物性参数。首先通过建立正演模型,将含有异常体的模型区域剖分成规则的矩形网格,在区域两边的钻孔中分别安置发射和接受装置,采用多点发射、多点接收的方法获得已知地质条件下的每条速度射线的走时值,而后根据线性回归的原则对所得的时间数据加入20%的噪声,采用医学中成熟的ART算法进行模型的反演计算,计算表明反演结果与正演模型十分地逼近,计算精度和速度都能达到满意的效果。 相似文献
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Luděk Klimeš 《Pure and Applied Geophysics》1996,148(3-4):539-563
A new computational scheme for calculating the first-arrival travel times on a rectangular grid of points is proposed. The new proposed method is of second-order accuracy. This means that the error of the calculated travel time is proportional to the second power of the grid spacing. The method should be sufficiently accurate for all applications in smooth seismic models. On the other hand, the method is not, in its present form, proposed for models with structural interfaces which make the method unstable and generate travel-time errors of the first order. Equations are also presented for the appropriate evaluation of the errors of calculated travel times to check their accuracy, and the proposed method is compared with other numerical methods. The method is developed, described and demonstrated in 2-D, but may also be extended to 3-D models and to general models with structural interfaces. 相似文献
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在Hudson理论的基础上推导出基于弹性—声学近似的裂缝模型反射系数计算公式,然后用变参考慢度Rytov近似波场延拓算子,对给定裂缝模型进行正演和偏移,并分析其波场特征,得到以下三点结论:1在当前地震分辨率下,不能识别单个裂缝,但可以探测裂缝发育带;2裂缝带达到一定的宽度和密度,可以用地震方法检测裂缝的分布,潜山内幕反射波的范围与强弱,有利于研究裂缝发育带的宽度和密度;3裂缝带的低频复波反射,表明在裂缝发育带,地震波频率减低,意味着用地震波的频率特征是可以检测裂缝。 相似文献