Fig. 1. Comparison between typical time traces of a wave propagating in a multiple scattering medium before and after a small perturbation: (a) The first arrival waves before and after a small perturbation; (b) the coda waves before and after a small perturbation.多散射介质中扰动前后波形的比较　(a) 直达波扰动前后的波形; (b)尾波扰动前后的波形

Fig. 2. Examples of sensitivity kernel based on the diffusion approximation in 2-D: (a) Spatial representation of the sensitivity kernel when t = 1 s; (b) spatial representation of the sensitivity kernel when t = 5 s; (c) vertical view of the sensitivity kernel when t = 1 s; (d) vertical view of the sensitivity kernel when t = 5 s. 基于扩散近似的二维敏感核示例　(a) t = 1 s时的敏感核空间分布; (b) t = 5 s时的敏感核空间分布; (c) t = 1 s时的敏感核俯视图; (d) t = 5 s时的敏感核俯视图

Fig. 3. 2-D velocity field model.二维速度场模型

Fig. 4. Layout of the source and receivers.激励源及接收点布设

Fig. 5. Case 1: (a) Inversion image of linear least squares method; (b) inversion image of the method in this paper.算例1　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Fig. 6. Case 2: (a) Inversion image of linear least squares method; (b) inversion image of the method in this paper.算例2　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Fig. 7. The results of experimental data processing: (a) Inversion image of linear least squares method; (b)inversion image of the method in this paper.实验数据处理结果　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Fig. 8. Case 3: (a) Inversion image of linear least squares method; (b) inversion image of the method in this paper.算例3　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Fig. 9. Case 4: (a) Inversion image of linear least squares method; (b) inversion image of the method in this paper.算例4　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Fig. 10. Case 5: (a) Inversion image of linear least squares method; (b) inversion image of the method in this paper.算例5　(a) 线性最小二乘法的反演图像; (b) 本文方法的反演图像

Table 1. The comparison of imaging time between linear least squares method and the method in this paper.