双平方根算子波场外推叠前偏移速度分析

Prestack migration velocity analysis via double squareroot operator wavefield continuation

1. 中国科学院数学与系统科学研究院计算数学与科学工程计算研究所,北京 100080;2. 中国科学院地质与地球物理研究所,北京 100101

Academy of Mathematics and System Sciences, Institute of Computational Mathematics and Scientific/Engineering Computing, Chinese Academy of Sciences,Beijing 100080,China

基于波场外推的叠前偏移具有较好的成像精度,但其成像精度又建立在精确的速度模型之上,利用叠前偏移对速度的敏感性来建立较好的速度模型是精确成像的重要保证。基于双平方根算子的波场外推,探讨了一种新的适应横向变速的叠前偏移速度分析方法。该方法首先在共中心点一半偏移距域中进行波场外推,然后根据波场外推的结果建立速度能量图并拾取速度信息,这个过程可根据需要作若干次迭代。对该方法的计算公式进行了推导,并设计了点散射体的常速模型和变速模型,进行了计算,计算结果表明了方法的正确性。该方法具有适应横向变速和倾角变化及计算量小的特点。

Prestack migration based on wavefield continuation is of high imaging precision when a precise velocity model is used. Utilization of the sensitivity of pres-tack migration to velocity in the construction of velocity model ensures precise imaging. Based on double square-root operator wavefield continuation, the author developed a new prestack velocity analysis method. Firstly wavefield continuation is implemented in CMP and half-offset domain Secondly a velocity-energy graph is plotted from the results of wavefield continuation. Finally velocity is picked up. This process can be repeated several times if needed. This paper presents the algorithm of the method. The correctness of method is tested on models with constant or variable velocity scatterers. The method is applicable in the case of laterally variable velocity and dip, and its computational cost is relatively small.