ABSTRACT

The severe rugged seabed interfaces bring great difficulties to seismic imaging in the marine environment. To accurately image submarine structures under the rugged seabed interface, an acoustic-elastic coupled curvilinear-coordinated least-squares reverse time migration (AE-CLSRTM) is proposed. This method is based on the coupled equation method, which uses the acoustic wave equations in seawater and the elastic wave equations in the underlying elastic medium. The pressure in the acoustic wave equations and the stresses in the elastic wave equations are transmitted steadily and continuously by using acoustic-elastic control equations at the seabed interface. To overcome the influence of the rugged seabed interface, the acoustic-elastic model is meshed into non-uniform curvilinear grids, and the corresponding mapping technique is used to transform the model with the rugged seabed interface to a horizontal one in the curvilinear coordinate system through the coordinate transformation. Based on the acoustic-elastic coupled equations in the curvilinear coordinate system, the acoustic-elastic coupled LSRTM algorithm in the rugged seafloor structure is realised. The numerical examples on a simple model and an actual area model show that the proposed LSRTM method can obtain the accurate imaging results of submarine structures in both P- and S-velocity components.

摘要

严重崎岖的海底界面给海洋环境中的地震成像带来了很大的困难。为了准确成像崎岖海底界面下的海底结构，提出了一种声-弹性耦合曲线-坐标最小二乘逆时偏移（AE-CLSRTM）。该方法基于耦合方程法，利用海水中的声波方程和下层弹性介质中的弹性波方程。声波方程中的压力和弹性波方程中的应力在海底界面采用声-弹控制方程稳定、连续地传递。为了克服崎岖海底界面的影响，声弹性模型被划分为非均匀曲线网格，并采用相应的映射技术，通过坐标变换将具有崎岖海底界面的模型转换为曲线坐标系中的水平模型。基于曲线坐标系中的声-弹耦合方程，实现了崎岖海底结构中的声-弹耦合LSRTM算法。简单模型和实际区域模型的数值算例表明，所提出的 LSRTM 方法可以在 P 和 S 速度分量中获得海底结构的准确成像结果。实现了崎岖海底结构中的声弹耦合LSRTM算法。简单模型和实际区域模型的数值算例表明，所提出的 LSRTM 方法可以在 P 和 S 速度分量中获得海底结构的准确成像结果。实现了崎岖海底结构中的声弹耦合LSRTM算法。简单模型和实际区域模型的数值算例表明，所提出的 LSRTM 方法可以在 P 和 S 速度分量中获得海底结构的准确成像结果。