面向崎岖海底构造环境的声-黏弹耦合介质最小二乘逆时偏移

In the complex sea area of China, the extremely rugged seabed structure is always a key problem for marine seismic imaging, restricting the development of marine seismic exploration technology. In addition, the viscoelasticity exists widely in the underground medium, resulting in inaccurate images under the conventional elastic assumption or viscoacoustic approximation. This research will propose an acoustic-viscoelastic coupling least-squares reverse time migration (LSRTM) for the rugged seabed environment. In the new method, forward modeling and wavefield separation in an acoustic-viscoelastic coupled medium with an extremely rugged seabed are proposed by using the adaptive nonuniform curvilinear grids. The object function, the adjoint operator and the demigration operator of acoustic- viscoelastic coupling LSRTM are constructed based on the P- and S-wave separation. Besides, the subspace step search method based on weighted coefficients is realized to estimate the steps of different parameters. This research can overcome the influence of rugged seabed, correct the viscoelasticity of the subseabed medium and improve the imaging quality of complex sea environment by using the inversion-based imaging method.

在我国复杂的海域地区，剧烈崎岖的海底构造一直是海洋地震成像的难点，制约着海洋地震勘探技术的发展，地下介质还广泛存在着黏弹性，采用常规的弹性假设或者黏声近似难以得到准确的成像结果。本项目将研发一种面向崎岖海底构造环境的声-黏弹耦合介质最小二乘逆时偏移方法，该方法针对剧烈崎岖海底构造发展基于自适应非均匀曲网格的声-黏弹耦合介质正演模拟及波场分离方法，构建基于纵横波场分离的声-黏弹耦合介质最小二乘逆时偏移的目标函数及伴随算子、反偏移算子，并针对多参数反演中不同参数的步长估计问题，实现基于加权系数的子空间步长搜索方法。本研究可以克服崎岖海底构造的影响，校正海底以下介质的黏弹性，利用反演成像方法改善复杂海洋环境的成像质量。

在我国复杂的海域地区，剧烈崎岖的海底构造一直是海洋地震成像的难点，制约着海洋地震勘探技术的发展，地下介质还广泛存在着黏弹性，采用常规的弹性假设或者黏声近似难以得到准确的成像结果。本项目研发了一种面向崎岖海底构造环境的声-黏弹耦合介质最小二乘逆时偏移方法，该方法针对剧烈崎岖海底构造发展了基于自适应非均匀曲网格的声-黏弹耦合介质正演模拟及波场分离方法，构建了基于纵横波场分离的声-黏弹耦合介质最小二乘逆时偏移的目标函数及伴随算子、反偏移算子，并针对多参数反演中不同参数的步长估计问题，实现了基于加权系数的子空间步长搜索方法。本研究克服了崎岖海底构造的影响，校正了海底以下介质的黏弹性，利用反演成像方法改善了复杂海洋环境的成像质量。