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在文献中,Kirchhoff型反偏移场的稳相分析主要是在下列两个条件下进行的:(1)等时面和目标反射面相切;(2)深度偏移像场信号的长度接近于零。对于与目标反射面不相切的等时面和长度远大于零的深度偏移像场子波,已有的结果将不再成立。为了在等时面和目标反射面不相切和深度偏移像场的子波长度远大于零的条件(一般条件)下对Kirchhoff型反偏移场进行稳相分析,我推导了出现在二维稳相分析公式中的诸因子的计算公式,并从中发现:(1)对于不同的等时面,距离差函数的稳相点具有不同的水平坐标;(2)Kirchhoff型真振幅反偏移的输出场由两部分(真振幅反偏移信号与振幅畸变因子)的乘积组成。由此得到下列两个结论:(1)一个给定的反偏移信号由多个深度偏移信号上的采样点组装而成,反偏移信号上的采样点个数等于对于这种组装有贡献的偏移信号的个数。(2)振幅畸变效应是Kirchhoff型反偏移中的固有效应,靠反偏移本身无法消除。如果一定要消除这种振幅畸变效应,必须对反偏移结果进行振幅校正。
In the literature, the stationary phase analysis of the Kirchhoff type back-shift field is mainly performed under the following two conditions: (1) the isochronism is tangent to the target reflection surface; (2) the depth-shifted image field signal has a length close to zero. For the isochronous surface that is not tangent to the target reflection surface and the depth-shifted image field wavelet whose length is far greater than zero, the existing result will not be valid. In order to perform a steady phase analysis of the Kirchhoff type back-shift field under the condition that the wave lengths of the isochronism and target reflection surfaces are not tangent and the depth of shift of the image field is far greater than zero (general condition), I derive the two- (1) For different isochronous surfaces, the steady-state points of the distance difference function have different horizontal coordinates; (2) the Kirchhoff-type real amplitude anti-skew The output field consists of the product of two parts (true amplitude inverse offset signal and amplitude distortion factor). This gives the following two conclusions: (1) A given reverse-shifted signal is assembled from sampling points on a plurality of depth-shifted signals equal to the number of sampling points on the reverse-shifted signal The number of contributing offset signals. (2) The effect of amplitude distortion is an inherent effect of Kirchhoff type anti-migration, which can not be eliminated by the anti-migration itself. If you must eliminate this effect of amplitude distortion, the amplitude of the backoff offset must be corrected.