Theoretical and Applied Case Studies of Seismic Imaging in Tunnelling

Seismic measurements during tunnel operations aim at images of maximum spatial resolution. However, there are still principal limitations of the method applied in the tunnel with regard to spatial resolution by the signal frequency and attenuation and by the small angular illumination coverage. A finite-difference simulation of elastic wave propagation had been performed to compute a synthetic tunnel seismic reflection survey. Synthetic data are used optimizing the best practice tunnel data processing sequence for both P- and S-waves because every step between the acquisition of the seismic data and the derivation of the final image influences the final seismic resolution. Here, especially the use of attenuation models compensate amplitude loss as well as dispersion by an inverse Q-filtering and the use of a spatially variable velocity model yielding the right image position of a reflecting geological element in space. The transfer and capability of this practice to real tunnel application is finally demonstrated by the case study of the tunnel seismic prediction method in the Koralm tunnel project in Austria.