基于分频编码的弹性波全波形反演

Elastic full waveform inversion based on frequencydivision encoding

计算量与计算效率限制了全波形反演方法的应用,震源编码技术可以有效减少全波形反演的计算量,提升反演效率。传统震源编码技术要求各炮具有相同的接收点排列,在观测系统适应性方面存在不足,无法直接应用于滚动排列观测系统。为此,提出一种基于分频编码的弹性波全波形反演方法,即在正演过程中仍可同时对多个炮记录进行正向延拓,给每一炮赋以不同频率的谐波震源,使同时进行正向延拓的各炮波场在频谱上互不重合;在炮点波场正传和残差反传过程中,采用相位灵敏度检测技术提取每炮的单频波场,实现各炮波场的完全分离,用于构建波形反演梯度,实现模型更新。同传统震源编码技术相比,该方法不受观测系统限制,能应用于排列滚动的观测系统,具有更广的应用范围。

The calculation amount and efficiency limit the application of full waveform inversion technology.Source coding technology can effectively reduce the calculation amount of full waveform inversion and improve the inversion efficiency.The traditional source coding technology requires that each gun has the same receiver array,and it has some shortcomings in the adaptability of the recording system,so it can not be directly applied to the recording system with rolling array.In this paper,an elastic full wave inversion method based on frequency-division coding is proposed.Its basic idea is:In forward process,multiple shot records can be extended at the same time,but each shot record is assigned with a harmonic source of different frequency,so the wave fields forward extended at the same time do not coincide with each other in the frequency spectrum.In the process of forward and residual backward propagation of the shot point wave field,phase sensitivity detection is used to separate the single-frequency wave field of each gun to realize the complete separation of the wave fields of each gun,and then the waveform inversion gradient is constructed to update the model.Compared with the traditional source encoding method,the simultaneous interpreting method can not only be speeded up in inversion,but also be applied to the recording system with rolling array in a wider field.