多尺度波形层析反演在高精度速度建模中的应用

Application of Multiscale Waveform Tomography Inversion in High-Accuracy Velocity Modeling

波形层析反演方法利用地震波的振幅和相位信息,通过波场重构获得地下参数信息,理论上可以获得更高精度和分辨率的速度模型。但由于受反演算法本身强非线性特征的影响,以及对初始模型依赖程度较高,波形层析反演技术在实际应用中难以取得理想效果。提出一种改进的多尺度反演方法,结合地质层位解释结果,建立较高精度的深度域偏移速度场作为波形层析反演初始输入模型,通过频率域波形层析算法实现多尺度反演降低反演的非线性,并将其成功应用于Marmousi数值模型和某海上实际资料处理。通过将改善后的深度域速度模型应用于Kirchhoff叠前深度偏移,成像结果与抽取的偏移距域共成像点道集对比结果显示,多尺度波形层析反演更新了更多的高频细节信息,提高了地震偏移成像的精度和分辨率。

The information of seismic amplitude and phase for reconstruction wave field can be used in waveform tomography inversionmethod to get a velocity model with higher accuracy and resolution theoretically. However, because of its serious nonlinearity and high de-pendence on initial velocity model, it often results in unsatisfactory inversion results in field application. This paper presents an improvedstrategy of multiscale inversion to establish higher-accuracy depth migration velocity field as an initial input model of waveform tomogra-phy, so that decrease the serious nonlinearity. This strategy is successfully applied to Marmousi model and case study, in which the updatedvelocity is used to make Kirchhoff pre-stack depth migration. The final result shows that the waveform tomography can retrieve much morehigh-frequency details and highly improve the accuracy and resolution of the seismic migration imaging.