Seismic Migration Imaging of Mountain Tunnel Using Surface Observation System

Tunnel seismic prediction (TSP) plays a critical role in ensuring the safety of tunnel construction; however, traditional methodologies encounter challenges related to detection range, system deployment, and imaging complexity. In this correspondence, we introduce a novel prestack time migration approach for TSP, known as the surface observation-based prestack time migration method for TSP (SOPSTM-TSP). This method involves the extraction of the direct wave through analysis of seismic wavelet characteristics to derive the scattered wave field, which is subsequently utilized for imaging the mountain through prestack time migration. Through numerical experimentation, the efficacy of the SOPSTM-TSP method is demonstrated in the identification of 5-m scatterers, detection of 60° dip faults, and characterization of relative velocity disparities within various geological contexts. A field study conducted in Gansu, China has demonstrated the feasibility of this method. Engineering practice has confirmed that a 30-m-long rock fracture zone corresponds to the migration results. SOPSTM-TSP uses the amplitude of imaging results to indicate the strength of lithology, which can guide tunnel construction more conveniently and safely.