基于包络目标函数的弹性波波形反演

Elastic full waveform inversion based on envelope objective function

弹性波场的复杂性致使反演问题非线性性增强,寻优过程极易陷入局部极值。多尺度反演能在一定程度上提高反演的稳定性及分辨率,但多尺度反演策略无法解决实际数据的低频缺失问题。针对该问题,提出了一种新的基于包络目标函数的弹性波多尺度反演策略。首先将包络反演方法应用到弹性波,恢复地下弹性介质参数中的低波数信息;然后将包络反演结果作为常规多尺度反演的输入,进一步提高反演的稳定性。Marmousi2模型试算结果表明该策略能够更加准确地反演纵、横波速度以及密度信息。

The complexity of elastic wavefield will increase the nonlinearity of inversion and make the inverse problem fall into local minima. Multi-scale inversion algorithms can improve the stability and resolution of inversion to a certain extent, but it cannot solve the problem o{ low frequency missing in real data. To alleviate this problem, we propose a new multi-scale scheme based on envelope inversion to obtain the elastic parameters accurately. The main procedures are as follows： Firstly, we extend the envelope inversion method to elastic medium to estimate the low wavenumber components o{ elastic parame- ters; then, the envelope inversion results are used as the initial model of conventional multi-scale inversion to further improve the stability of the inversion. The Marrnousi2 model test results show that the new multi-scale scheme can estimate P- and S- wave velocities more accurately, as well as the density information.