Self-supervised learning waveform inversion for seismic forward prospecting in tunnels: A case study in Pearl River Delta Water Resources Allocation Project in China

ABSTRACT Tunnel and underground engineering construction often encounter unfavorable geology, leading to disasters such as water and mud inrushes and landslides. To prevent geologic hazards, it is important to look ahead and predict the location and distribution of adverse geology ahead of the tunnel face. This process is known as seismic forward prospecting in tunnels, and it typically requires an accurate calculation of velocity. Seismic waveform inversion methods based on deep learning have demonstrated potential in estimating velocity from synthetic seismic data. However, the superiority of these methods over traditional ones on field data is still an area of active research. Here, the Pearl River Delta Water Resources Allocation Project in China is used as an example to develop a self-supervised learning waveform inversion method for building a reliable velocity distribution in front of the tunnel. By introducing the background velocity as large-scale information and implementing multiscale loss functions, the previous self-supervised learning inversion method on synthetic data is improved. In addition, the corresponding network-based workflow for field data is developed. To demonstrate the effectiveness of our method, a comparison is conducted with practical tunneling exposure, for which the low-velocity zone corresponds with the fault-fractured zones and the water-flowing zones. This indicates that the results obtained from our method can be used as geologic guidance for safe tunneling practices. In the end, the applicability and disadvantages of our deep-learning inversion method for seismic forward prospecting in tunnels are discussed.