Abstract
Migration imaging is a key step in tunnel seismic data processing. Due to the limitation of tunnel space, tunnel seismic data are small-quantity, multi-component, and have a small offset. Kirchhoff migration based on the ray theory is limited to the migration aperture and has low migration imaging accuracy. Kirchhoff migration can no longer meet the requirements of high-precision migration imaging. The reverse time migration (RTM) method is used to realize cross-correlation imaging by reverse-time recursion principle of the wave equation. The 3-D RTM method cannot only overcome the effect of small offset, but also realize multi-component data imaging, which is the most accurate migration method for tunnel seismic data. In this paper, we will study the 3-D RTM method for multi-component tunnel seismic data. Combined with the modeled data and the measured data, the imaging accuracy of the 3-D Kirchhoff migration and 3-D RTM is analyzed in detail. By comparing single-component and multi-component Kirchhoff migration and RTM profile, the advantages of the multi-component RTM method are summarized. Compared with the Kirchhoff migration method, the 3-D RTM method has the following advantages: (1) it can overcome the effect of small offset and expand the range of migration imaging; (2) multi-component data can be realized to improve the energy of anomalous interface; (3) it can make full use of multiple waves to realize migration imaging and improve the resolution of the anomalous interface. The modeled data and the measured data prove the advantages of the 3-D multi-component RTM method.
Highlights
The tunnel seismic advance prediction method is one of the most effective geophysical methods for the prediction of long-distance geological disasters in the tunnel
The Kirchhoff migration method based on ray theory has low requirements regarding the accuracy of the velocity model, obvious advantages in the stability and efficiency of the calculation results, and has achieved good results in the migration imaging processing of ground seismic data [21]
Due to the limitation of migration aperture, the Kirchhoff migration method based on the ray theory cannot distinguish the vertical and horizontal anomalous interfaces in the migration profile (Figure 14a)
Summary
The tunnel seismic advance prediction method is one of the most effective geophysical methods for the prediction of long-distance geological disasters in the tunnel. This can accurately predict the geological anomalous from 100 m to 150 m, including fault fracture zone, karst cave, soft rock, and water-rich zone. Migration imaging is one of the core technologies of tunnel seismic data processing. The narrow tunnel space limits the acquisition of seismic data in the tunnel, which gives the tunnel seismic data the characteristics of a small offset, multiple components, and a small data volume. Some scholars have studied the tunnel seismic data migration imaging method.
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