A history of tunnels and using active seismic methods to find them

The modern use of clandestine tunnels has antagonized military and law enforcement agencies alike over the past 50 years, not only in their simplicity and effectiveness, but also in the challenges of defending against them. Likewise, geophysicists have been confounded, finding what should be a straightforward target on paper — detecting an anomaly with often vastly different physical properties than its surroundings — a much more difficult task than models would suggest. We have evaluated half a century of applied seismic investigation, gaining a history of the use of active seismic methods to detect subterranean tunnels in war zones, along borders, and around facility perimeters. Previously published studies using a variety of seismic methods such as reflection, refraction, surface waves, diffraction, resonance, and full-waveform inversion were aggregated to serve as a reference for void and tunnel detection-related research and to show the progression of the methods used over time.