3D tunnel space elastic reverse time migration in cylindrical coordinates using reconstructed time-domain wavefields

Seismic advance detection is a method for detecting complex geological formations in a tunnel face, which is crucial for the safe construction of tunnel projects. During the process of three-dimensional (3D) reverse time migration (RTM) imaging, the wavefield complexity in tunnel space is exacerbated by the cylindrical cavity and the storing and reading of a source wavefield spatiotemporal sequence, which affects the precision of exploration results and the data Input/Output (I/O) consumption. Therefore, we propose an elastic RTM of wavefield reconstruction based on the representation theorem with the equivalent source method in cylindrical coordinates of 3D tunnel space. This method can reduce the demand for storage space exhibited by the source wavefield and lay the foundation for RTM imaging using a higher-precision and larger-size cylindrical coordinates model. To obtain detection results that exhibit more precision and a wider range of detection in tunnel advance detection technology, this study constructs a complicated geological formations model ahead of the tunnel and utilizes this method to perform 3D RTM imaging. The results indicate that the proposed method can effectively realize RTM imaging in cylindrical coordinates for the exploration of complicated geological formations in 3D tunnel space based on the wavefield reconstruction of the representation theorem with equivalent source injection.