【摘要】 叠前逆时偏移将是应用前景最为广泛的地震偏移技术,但存在计算量大和存储单元要求多的瓶颈问题.随机边界条件思想的提出较好地解决了其中的存储问题,但同时也大大增加了计算成本.为了减小边界宽度,降低宽边界带来的计算负担,同时又不影响随机边界的随机效果,本文首先提出了一种多形式随机边界函数,并从随机介质散射理论出发,研究了随机边界的散射特性,并将随机边界归纳为增强模式和衰减模式两类,深入分析推导了不同模式边界的随机函数形式选择的最优判据,最后形成了一套能够使得在边界宽度有限情况下获得最佳散射效果的随机边界构建算法.理论分析和数值模拟实验结果表明:在边界宽度较窄的情况下,利用本文提出的随机边界构建策略,能够最大程度地发挥有限宽随机边界散射性能,压制相干能量的产生.这为提高随机边界的随机性能,减小随机边界的宽度,提高逆时偏移的计算效率提供了一种有效的方法.更多还原

【Abstract】 Pre-stack reverse-time migration(RTM) will be the most promising migration method to be widely used in the future,but it has some bottleneck problem such as highly intense computational expense and massy memory demand.The thinking of random boundary condition(RBC) for RTM is an efficient way to solve the storage issue,however it immensely increases the computation cost meanwhile.This paper tries to promote the computing efficiency,hopefully with no influence for random effect of the boundary,by the way of decreasing the width of boundary.Firstly,the random boundary function(RBF) with multiple forms was put forward.In the light of random media scattering theory,the scattering features of the random boundary build with various RBF were detailedly analyzed.Secondly,we summed up random boundaries into two types,including enhanced mode and evanescent mode,based on the statistic property of the boundary build with a certain RBF.Finally,through theoretically derivation and semi-quantitative analysis,an optimized strategy for random boundary building was summed up,which is able to make the boundaries yielding the greatest returns on limited investment.Theoretically analysis and modeling results indicate that the random boundaries,build by this optimized random boundary building strategy under limited width,can still have a wonderful boundary effect to suppress the generation of coherent energy.This method can effectively improve the computing efficient in RTM.更多还原