Seismic Imaging and Detection of Underground Tunnels

To investigate the problem of detecting and imaging underground tunnels, an experimental system that utilizes seismic waves has been constructed. Seismic reflections from the tunnel are transformed into a 3D image using a synthetic aperture time-delay backprojection algorithm. Results from experimental data show that the tunnel is directly visible in the backprojected image. Nevertheless, tunnels with low signal to noise ratio (SNR) are located using 2D and 3D Radon Transforms followed by a detection algorithm. A simulation is performed on the performance of the Radon transform for detecting lines in noisy images and it is shown how lines in very low SNR images can be detected. Also it is observed that longer lines have higher probability of detection at the same noise level.