Bureau of Sabotage
Notes From the Underground: The Long History of Tunnel Warfare
CGround-penetrating radar has been one promising area of research, using pulses of radio frequency energy to find voids or gaps beneath ground surface. GPR works fine for locating utility lines and minesweeping operations and finding buried historical sites. But looking deeper, to the 10- to 20-meter depths where terrorists like to lay their tunnels, is more difficult. Lockheed Martin is working with the DHS on a lower-frequency version of GPR, using electromagnetic waves to plot tunnels deep underground, but until now the results have been indeterminate.
Another promising approach is the prototype Active Acoustic Tunnel Detector, being developed at Idaho National Laboratory, which transmits up to 200 hertz of acoustic waves into the ground. An onboard motion detector measures how the waves move the dirt and rock that those sound waves pass through. If the ground is solid, the resulting graph shows a rapidly rising line. If there’s a gap or void, the graph line will appear as a hump or dip. A third approach uses microgravity analysis, measuring minute changes in the planet’s gravitational field to locate a tunnel. That requires a higher level of precision than current testing can show and will require a heavy investment in research to get any reliable results.