Nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media
Nonlinear traveltime inversion scheme for crosshole seismic tomography in tilted transversely isotropic media
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DOI：
10.1190/1.2910827
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发表时间：
2008-05
期刊：
影响因子：
3.3
通讯作者：
Bing Zhou;S. Greenhalgh;A. Green
中科院分区：
文献类型：
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作者：
Bing Zhou;S. Greenhalgh;A. Green
井间地震层析成像通常用于对井间介质的速度结构进行成像。如果岩石具有各向异性，则层析技术必须适应复杂的情况；否则，就会导致错误的解释。我们提出了一种在已知倾斜对称轴的复合横观各向同性介质中进行井间地震层析成像的非线性运动反演方法。该方法基于新版本的一阶走时扰动方程。它直接使用相速度的导数而不是体波模式的特征向量来克服应用于两个准剪切波的奇异性问题。我们应用了迭代非线性求解器，结合了我们的运动学光线追踪方案，并直接计算任意参考介质中的雅可比矩阵。这根据强和弱各向异性介质中三个地震体波（qP、qSV、qSH）的初至走时重建了五个弹性模量或汤姆森参数。我们进行了三个综合实验，包括确定均质岩石的各向异性参数、重建嵌入强各向异性背景中的断层以及对包含小通道和埋藏倾斜界面的复杂四层模型进行成像。我们将各向同性层析成像非线性反演方法的结果与传统线性各向异性反演方案的结果进行了比较，这表明了新方案在跨孔层析成像方面的能力和优越性。
Crosshole seismic tomography often is applied to image the velocity structure of an interwell medium. If the rocks are anisotropic, the tomographic technique must be adapted to the complex situation; otherwise, it leads to a false interpretation. We propose a nonlinear kinematic inversion method for crosshole seismic tomography in composite transversely isotropic media with known dipping symmetry axes. This method is based on a new version of the first-order traveltime perturbation equation. It directly uses the derivative of the phase velocity rather than the eigenvectors of the body-wave modes to overcome the singularity problem for application to the two quasi-shear waves. We applied an iterative nonlinear solver incorporating our kinematic ray-tracing scheme and directly compute the Jacobian matrix in an arbitrary reference medium. This reconstructs the five elastic moduli or Thomsen parameters from the first-arrival traveltimes of the three seismic body waves (qP, qSV, qSH) in strongly and weakly anisotropic media. We conducted three synthetic experiments that involve determining anisotropic parameters for a homogeneous rock, reconstructing a fault embedded in a strongly anisotropic background, and imaging a complicated four-layer model containing a small channel and a buried dipping interface. We compared results of our nonlinear inversion method with isotropic tomography and the traditional linear anisotropic inversion scheme, which showed the capability and superiority of the new scheme for crosshole tomographic imaging.