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Christopher Riedel, Khayal Musayev, Matthias Baitsch, Klaus Hackl

• With the knowledge of the geology in front of a tunnel, the excavation process can be optimized to avoid damage at the tunnel boring machine and settlements on the surface. Therefore, dwell times can be decreased and additional expenses can be avoided. Transmitted seismic waves will be spread, reflected and refracted due to geological changes. By utilizing geophones, the seismic waves will be captured and information about the geological structure in front of the tunnel can be extracted from the measured seismograms using e.g. the concept of full waveform inversion. A frequency domain model has been employed to demonstrate the potential of full waveform inversion for seismic reconnaissance in a tunnel environment. The success of the inversion procedure depends strongly on the positions of the utilized sender and receiver stations, the chosen initial material parameter distribution, and on the selected frequency groups for the inversion. Further challenges are an accurate representation of the reflecting surfaces and the application of absorbing borders to oppress reflections from the artificial boundaries, which delimit the analyzed domain. The results of the performed full waveform inversion for synthetic models of a 3D tunnel configuration with different disturbances ahead of the front tunnel face will be discussed. Additionally, the influence of different locations of the sender and receiver stations will be analyzed.