Detection and Imaging of Underground Structures by Exploiting ELF/VLF Radiowaves
Abstract
Clandestine tunnels and underground complexes have been developed in recent years to conceal border crossing passageways and military assets. Ground or airborne attack requires overt and covert imaging to determine the orientation of the underground facility, classification of the overlying rock/soil, burial depth, location of adits, and power and communication lines. Standard worldwide mining practice causes electrical conductors to be installed in the adit and passageways of the underground complex. These electrical conductors form low attenuation rate networks for distribution of EM waves throughout the complex. The electric field component of the primary (illuminating) EM wave induces current flow in these conductors. The current flow causes cylindrically spreading secondary waves to propagate in the surrounding rock mass and become observable on the surface. Mapping the observable provides the information needed for detection. Both analytical codes to determine the underground complex response and highly effective instrumentation for measuring secondary waves have been developed. The High Frequency Active Auroral Research Project transmitter produces and EM wave magnetic field component that is measurable on the earth's surface, making it an effective standoff transmitter for evaluating detection technologies.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 14, 2000
- Accession Number
- ADA404941
Entities
People
- Larry G. Stolarczyk