In this work, we combine the local perturbation beamlet migration theory and the concept of survey sinking prestack depth migration. We prove the equivalence between the propagators in source-receiver survey sinking migration and the shot domain beamlet migration. In this algorithm, the frequency domain common point source and point receiver wavefield is first decomposed by the local cosine basis along common sources and receivers, and then the decomposed wavefield is downward-continued to the next depth along common beamlet-sources and beamlet-receivers subsequently. The propagated wavefield is equivalent to the data that would have been received if all sources and receivers were placed at the current depth. The migrated image is evaluated at zero time and zero offset. Numerical tests on synthetic data of the 2D SEG/EAGE salt model and the Marmousi model demonstrate the validity of the theory and the good accuracy of the beamlet method on strong contrast velocity model and complex geology structures.%将局部余弦基小波束波场分解、传播与观测系统沉降法叠前深度偏移相结合,推导了源-检波器观测系统沉降法传播算子.本算法中,先对频率域的共点源和共点检波器道集做局部余弦小波束分解,然后分别沿共小波束源和共小波束检波器在深度方向延拓得到下一层波场.每个深度的波场,都等效于把源和检波器放在该层后所能接收到的地震记录,每点的像值由炮点和检波点重合时的零时刻波场值给出.通过二维SEG/EAGE盐丘模型和Marmousi模型的偏移成像结果验证该方法理论推导的正确性.另外,结果显示该方法继承了小波束域波场延拓在速度扰动较大情况下波传播及成像精度高的优点.
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