基于反射地震数据的时频域包络反演

Reflection seismic data based envelope inversion in the time-frequency domain

包络信号含有丰富的低频分量,即使在地震数据缺失低频条件下,包络目标函数也能有效缓解全波形反演的周期跳跃现象.但是,当初始速度模型较为平滑时,观测数据中的反射地震事件在模拟数据中没有与之相对应的波形,导致包络反演初期无法很好地利用反射波信号进行速度建模.本文提出基于反射地震数据的时频域包络反演方法,通过结合反射波全波形反演理论,构建反射波时频域包络目标函数,来提高包络反演的速度建模精度.本文首先利用Gabor变换获取时频域地震数据,并提取振幅信息,即为时频域包络信号.然后,推导反射波时频域包络反演的伴随震源和梯度算子.Marmousi模型数据测试结果表明,基于反射地震数据的时频域包络反演方法可以为全波形反演提供一个较好的初始速度模型.

Envelope signals contains abundant low-frequency components, even if the seismic data lack low-frequencies, envelope misfit can effectively mitigate the cycle skipping problem of Full Waveform Inversion(FWI). However, when the initial velocity model is smooth, the reflected seismic event in the observed data does not have a corresponding waveform in the synthetic data, which results in the inability to make good use of the reflection data for velocity modeling in the early stage of envelope inversion. This paper proposes to use the reflection seismic data to conduct the envelope inversion in the time-frequency domain. By combining the theory of reflection FWI, the time-frequency domain envelope misfit function is established to improve the velocity modeling accuracy. This article first uses Gabor transform to obtain time-frequency domain seismic data, then extracts the amplitude information, which is regarded as time-frequency domain envelope signals. After that, the gradient operator and adjoint source of the time-frequency reflection envelope inversion are derived. Finally, the Marmousi model tests show that the reflection seismic data based envelope inversion can provide a better initial velocity model for the FWI method.