When seismic exploration is conducted in a special geological environment such as a tunnel space, the traditional imaging method in the Cartesian coordinate system cannot accurately discretize the air column in that environment. Thus, obtaining Thus, obtaining high-quality imaging results is difficult. Therefore, an elastic-wave reverse-time migration method based on the polar coordinate system is proposed. In this method, three boundary conditions exist: outer, inner, and corner boundaries. In the outer boundary, the polar-coordinated absorbing boundary in the radial direction is used to suppress the artificial-boundary reflection. The free-surface boundary condition is adopted in the tunnel space at the inner boundary. In the angular boundaries, we use two different boundary conditions for two cases. The air column in the tunnel space is usually not an irregular circle. Therefore, the irregular tunnelspace geological body in the polar coordinate system is meshed into curvilinear grids and transformed into a regular one in an auxiliary polar coordinate system using the mapping method. Finally, elastic reverse-time migration technology is applied into the auxiliary polar coordinate system. In the numerical examples, two typical models are used to test the proposed method, which verify that the proposed method can obtain accurate images from the datasets in the tunnel space.

当在特殊的地质环境（例如隧道空间）中进行地震勘探时，笛卡尔坐标系中的传统成像方法无法准确地离散该环境中的气柱。因此，难以获得高质量的成像结果。因此，提出了一种基于极坐标系的弹性波逆时偏移方法。在此方法中，存在三个边界条件：外部边界，内部边界和拐角边界。在外边界中，使用径向上的极坐标吸收边界来抑制人工边界反射。内边界处的隧道空间采用​​自由表面边界条件。在角度边界中，对于两种情况，我们使用两种不同的边界条件。隧道空间中的气柱通常不是不规则的圆。因此，极坐标系统中的不规则隧道空间地质体被网格化为曲线网格，并在辅助极坐标系统中使用映射方法转换为规则网格。最后，将弹性逆时偏移技术应用于辅助极坐标系。在数值示例中，使用两个典型模型测试了该方法，验证了该方法可以从隧道空间中的数据集中获取准确的图像。弹性逆时偏移技术应用于辅助极坐标系。在数值示例中，使用两个典型模型测试了该方法，验证了该方法可以从隧道空间中的数据集中获取准确的图像。弹性逆时偏移技术应用于辅助极坐标系。在数值示例中，使用两个典型模型测试了该方法，验证了该方法可以从隧道空间中的数据集中获取准确的图像。