有限差分偏移截断误差及其传递因子相角分析

讨论截断误差与误差传递因子相角的影响与决定因素 ,以寻求有限差分波动偏移的合理采样步长。用三种波场函数来模拟实际波场进行理论计算。结果表明 :时间采样步长Δt是截断误差的主导因素 ,空间采样步长Δx(横向 )和Δz(深度方向 ) ,尤其是Δx影响甚小。依据空间点变化时截断误差的变化规律 ,提出了变步长偏移法。分析误差传递因子相角等因素对有限差分波动方程偏移造成的相位畸变问题 ,找到相应规律。综合考虑截断误差及误差传递因子相角 ,给出了合理采样步长。

ANALYSIS OF THE CUT-ERROR AND THE PHASE ANGLE OF ERROR TRANSFER FUNCTION IN THE FINITE DIFFERENCE MIRGATION

Cut-error that made from the finite difference mirgation,phase angle of error transfer function and factors that determine their values are discussed.Three functions of the different sense of the real wavefield are put forward and analysed respectively.We can see the value of the step of time is the dominant factor of cut-error,on the contrary,the steps of z and x are secondary.Changeable step mirgation is advanced.The aberration of phase depends on cut-error, and the phase angle of error transfer function is talked over.At last ,the reasonable values of t,z and x are gained by the efficiency function.