一种基于逆时偏移的高效照明补偿成像方法

An efficient illumination compensation imaging method based on reverse-time migration

对地震波偏移成像而言,由于观测采集系统不规则、不完备采样以及地下复杂构造对波场传播的影响,在成像点处通常存在照明不均匀的现象,对偏移成像结果进行照明补偿是提高地质体成像精度的有效方法.本文给出了一种基于逆时偏移实现的高效照明补偿成像方法.在高频近似下,本文首先定义了衡量地下照明均匀程度的雅克比矩阵,并以此为基础给出照明补偿算子.通过波场的边界积分表达式,进一步将照明补偿算子利用外推波场进行表达,避免了照明补偿算子中高频格林函数的显式计算,以此构造出高效的照明补偿成像算法.合成数据和实际数据的数值实验结果验证了本文提出方法的正确性.

For seismic imaging,due to irregular and finite sampling in acquisition geometry and the complexity of the subsurface,uneven illumination exists usually around an imaging point.The illumination compensation is an effective way to improve the imaging quality in this case.In this paper,we propose an efficient illumination compensation imaging method based on Reverse-Time Migration(RTM).Under high frequency approximation,we firstly define a Jacobian matrix that measures the regularity of subsurface illumination,then an illumination compensation operator is constructed based on this matrix.Through boundary integration,we further express the illumination compensation operator by the extrapolated wavefields,thus avoiding the explicit computation of asymptotic Green′s function and an efficient illumination compensation implementation for RTM is achieved.Numerical tests on both synthetic and field data validate the effectiveness and efficiency of the proposed method.