On the influence of model parametrization in elastic full waveform tomography
On the influence of model parametrization in elastic full waveform tomography
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DOI：
10.1111/j.1365-246x.2012.05633.x
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发表时间：
2012-10
影响因子：
2.8
通讯作者：
D. Köhn;D. Nil;A. Kurzmann;A. Przebindowska;T. Bohlen
中科院分区：
文献类型：
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作者：
D. Köhn;D. Nil;A. Kurzmann;A. Przebindowska;T. Bohlen
弹性全波形层析成像（FWT）旨在减少记录数据与建模数据之间的不拟合，从而推导出地下弹性材料参数的非常详细的模型。待反演弹性模型参数的选择影响着重建地下模型的收敛性和质量。利用交叉三角平方（CTS）模型，研究了具有爆炸点源和自由面条件的远距反射地震采集几何图形的三个弹性参数，即Lame参数m1 = [λ, μ, ρ]，地震速度m2 = [Vp, Vs， ρ]和地震阻抗m3 = [Ip, Is, ρ]。在每个CTS模型中，三个弹性参数分配给三个不同的空间分离的几何对象。CTS模型的研究结果表明，密度模型的重构需要从低频到高频的顺序频率反演。仅使用高频数据，串扰伪影对材料参数的定量重建有影响，而对于顺序频率反演，只存在代表不同模型参数边界的结构伪影。在反演过程中，可以很好地重建拉米参数、地震速度和阻抗。然而，使用Lame参数化-伪影存在于λ模型中，而当使用地震速度或阻抗时，类似的伪影被抑制。密度反演在所有参数化中显示出最大的模糊性。然而，当使用Lame参数并抑制地震速度和阻抗参数化时，伪影再次占据主导地位。上述结果在地质上更为真实的修正Marmousi-II模型上得到了证实。利用传统的拖缆采集几何图形，成功地重建了地下p -速度、s -速度和密度模型，并与Lame参数反演结果进行了比较。
SUMMARY Elastic Full Waveform Tomography (FWT) aims to reduce the misfit between recorded and modelled data, to deduce a very detailed model of elastic material parameters in the underground. The choice of the elastic model parameters to be inverted affects the convergence and quality of the reconstructed subsurface model. Using the Cross-Triangle-Squares (CTS) model three elastic parametrizations, Lame parameters m1 = [λ, μ, ρ], seismic velocities m2 = [Vp, Vs, ρ] and seismic impedances m3 = [Ip, Is, ρ] for far-offset reflection seismic acquisition geometries with explosive point sources and free-surface condition are studied. In each CTS model the three elastic parameters are assigned to three different geometrical objects that are spatially separated. The results of the CTS model study reveal a strong requirement of a sequential frequency inversion from low to high frequencies to reconstruct the density model. Using only high-frequency data, cross-talk artefacts have an influence on the quantitative reconstruction of the material parameters, while for a sequential frequency inversion only structural artefacts, representing the boundaries of different model parameters, are present. During the inversion, the Lame parameters, seismic velocities and impedances could be reconstructed well. However, using the Lame parametrization -artefacts are present in the λ model, while similar artefacts are suppressed when using seismic velocities or impedances. The density inversion shows the largest ambiguity for all parametrizations. However, the artefacts are again more dominant, when using the Lame parameters and suppressed for seismic velocity and impedance parametrization. The afore mentioned results are confirmed for a geologically more realistic modified Marmousi-II model. Using a conventional streamer acquisition geometry the P-velocity, S-velocity and density models of the subsurface were reconstructed successfully and are compared with the results of the Lame parameter inversion.