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1 Acta Geophysica

1 2023

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An efficient low-frequency artifact suppression method at excitation time for excitation amplitude imaging condition

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Wang R. , Wang D. , Hu B. , Zhang W. , Zhou J. , Li B.

tom Vol. 71, no. 3

1225--1240

The excitation amplitude imaging condition (EAIC) is a high-resolution, computationally efficient, and low-storage imaging condition in reverse time migration (RTM). However, when there are strong reflection interfaces in the velocity model, they will produce low-frequency artifacts, which seriously contaminate the RTM image. The artifacts can be removed by the wavefield decomposition algorithm, but this process always performed by analytic time wavefield extrapolation, which needs extra wavefield extrapolation. Furthermore, an extra source wavefield extrapolation is required to determine the excitation time before the migration. Thus, the additional wavefield extrapolations can seriously damage the computationally efficient advantage of the EAIC. By taking advantage of the directivity and low storage of excitation amplitude, we present a low-frequency artifact suppression method with no extra wavefield extrapolation. Poynting vector, reference traveltime and minimum amplitude threshold are combined to constraint the excitation amplitude updating process, and it makes the excitation amplitude more consistent with the definition of excitation criterion. We can directly obtain a noise-free excitation amplitude without the source wavefield decomposition. Instead of the analytic time wavefield extrapolation, the time-bin technique and the windowed Hilbert transform are combined to achieve the receiver wavefield decomposition only at the excitation time. The numerical results show that our method can effectively suppress the low-frequency artifacts in the image with no extra wavefield extrapolation.