基于逆散射成像条件的转换波弹性波动方程自动偏移速度分析

在地震偏移成像过程中, 成像精度依赖于速度模型, 因此偏移速度分析对高精度叠前偏移成像至关重要。基于高频近似下的逆散射成像条件, 提出了基于剩余曲率分析的转换波弹性波动方程偏移速度分析方法。首先基于高频近似下的逆散射成像条件, 采用逆时偏移近似估计转换S波散射位, 然后结合入射P波和转换S波散射位, 重构得到上行转换S波, 最后利用伴随状态法导出剩余时差关于波速的梯度。基于逆散射成像条件, 有效保证了弹性波动方程偏移速度分析中梯度的稳定求解。数值实验表明该方法导出了高质量的梯度。初步测试表明反演的速度模型有效地校平了共成像点道集, 改善了成像质量。此外, 剩余时差曲率智能识别等技术简化了中间处理流程, 构建的智能化速度分析框架有望提升计算效率。

In the process of seismic imaging, the accuracy of prestack migration imaging depends on the migration velocity model; therefore, migration velocity analysis is crucial for high-precision imaging. Based on the inverse scattering imaging condition under a high-frequency approximation, this paper proposes a converted phase elastic wave equation migration velocity analysis method. First, based on the inverse scattering imaging condition under a high-frequency approximation, the converted S-wave scattering potential was estimated by reverse time migration. The upward-converted S-wave was then reconstructed by combining the incident P-wave and the converted S-wave scattering potential. Finally, the gradient of the objective functional with respect to velocity was derived using the adjoint state method. The inverse scattering imaging condition effectively ensured a stable solution for the migration velocity analysis of the gradient elastic wave equation. A numerical experiment demonstrated that the proposed method produced a high-quality gradient. According to the preliminary experimental results, the inverted S-wave velocity effectively flattened the common image gathers and improved imaging quality. In addition, the intelligent recognition technology for the curvature of the residual moveout simplifies the intermediate processes, and the proposed intelligent velocity analysis framework likely improves the computational efficiency.