Smoothing imaging condition for shot-profile migration
Smoothing imaging condition for shot-profile migration
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DOI：
10.1190/1.2712113
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发表时间：
2007-04
期刊：
影响因子：
3.3
通讯作者：
A. Guitton;A. Valenciano;D. Bevc;J. Claerbout
中科院分区：
文献类型：
--
作者：
A. Guitton;A. Valenciano;D. Bevc;J. Claerbout
在成像条件中加入上行波场与下行波场在时间域上的除法反褶积，可以提高炮检剖面偏移的振幅。这种划分可以通过引入最佳维纳滤波器来增强，该滤波器假定数据中存在的噪声具有白色谱。这种假设需要一个阻尼参数，与信噪比有关，通常通过试验和错误来选择。实际上，阻尼参数代替下行波场频谱的小值，避免了被零除。偏移结果可能对阻尼参数相当敏感，并且在大多数应用中，上行和下行波场被简单地相乘。或者，可以通过用相邻点的平均值填充频谱的小值来使分割稳定。这种平均是通过对下行波场的频谱运行平滑算子来获得的。这种操作称为平滑成像条件。结果表明，当下行波场的频谱较高时，采用阻尼和平滑的成像条件得到了相似的结果，从而校正了照明效应。在频谱较低的情况下，平滑成像条件往往对数据中存在的噪声水平更鲁棒，从而给出比具有阻尼的成像条件更好的图像。此外，我们的实验表明，平滑成像条件的参数化，即，平滑算子的窗口大小的选择，从一个数据集到另一个数据集是容易和可重复的，使其成为一个有价值的补充ourimagingtoolbox。
Amplitudes in shot-profile migration can be improved if the imaging condition incorporates a division deconvolution in the time domain of the upgoing wavefield by the downgoing wavefield. This division can be enhanced by introducing an optimal Wienerfilterwhichassumesthatthenoisepresentinthedatahas a white spectrum. This assumption requires a damping parameter, related to the signal-to-noise ratio, often chosen by trial and error. In practice, the damping parameter replaces the small valuesofthespectrumofthedowngoingwavefieldandavoidsdivision by zero. The migration results can be quite sensitive to the damping parameter, and in most applications, the upgoing and downgoing wavefields are simply multiplied. Alternatively, the division can be made stable by filling the small values of the spectrumwithanaverageoftheneighboringpoints.Thisaveraging is obtained by running a smoothing operator on the spectrum ofthedowngoingwavefield.Thisoperationcalledthesmoothing imaging condition. Our results show that where the spectrum of the downgoing wavefield is high, the imaging condition with dampingandsmoothingyieldssimilarresults,thuscorrectingfor illumination effects. Where the spectrum is low, the smoothing imaging condition tends to be more robust to the noise level present in the data, thus giving better images than the imaging condition with damping. In addition, our experiments indicate that the parameterization of the smoothing imaging condition, i.e., choice of window size for the smoothing operator, is easy and repeatable from one data set to another, making it a valuable additiontoourimagingtoolbox.