FACTORIZATION SYNTHESIZED-SHOT PRESTACK DEPTH MIGRATION IN THE HELICAL COORDINATE SYSTEM
螺旋坐标下的因子分解合成炮叠前深度偏移

Based on the synthesized-shot prestack depth migration,a new high efficient method for the synthesized-shot prestack depth migration is proposed.It is a hybrid technique which implements wavefield extrapolation with factorization in the helical coordinate system. The wavefield extrapolation is divided into two explicit solving processes. One is a causal process, and the other is an anticausal process. Such explicit solving processes in the helical coordinate system can improve the wavefield extrapolation efficiency. Moreover, based on the phase encoding principle, the synthesized-wavefield corresponding to multiple ray parameters is encoded and stacked. Then the calculations are implemented with MPI parallel algorithm based on the ray parameters. Thus the calculation efficiency is enhanced further. After deriving the relevant formulae and analyzing the computation cost quantitatively, numerical calculations for the Marmousi complex model are carried out and results comparisons are made. The imaging results show that the method presented in this paper has the advantages of high precision and good efficiency. So it can be applied to practical data processing.