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January 2005

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Presented at the 2005 Symposium on the Application of Geophysics to Engineering and Environmental Problems (SAGEEP) byJose L. Llopis, Joseph B. Dunbar, Lillian D. Wakeley, Maureen K. Corcoran, U.S. Army Engineer Research Development Center, Vicksburg, Mississippi Dwain K. Butler, Alion, Inc., Vicksburg, Mississippi Abstract: The U.S. Army Engineer Research and Development Center (ERDC) has worked with U.S. Law Enforcement Agencies (LEAs) since 1995 to address the problem of clandestine tunnels beneath the U.S./Mexico border. ERDC has performed tunnel-related research, equipment development, or tunnel- detection missions at the request of the LEAs, coordinated by Joint Task Force 6 (JTF-6, Fort Bliss, TX, now known as JTF-N for Northern Command, US Army). This support to LEAs has revealed the importance of understanding the geologic context of a suspected tunnel site as a basis for selecting the appropriate geophysical tools and interpreting anomalies indicated by geophysical data. Tunnel detection missions always involve multiple tools and techniques. A combination of geophysical instruments is used to record data based on different physical principals. When interpreted in a regional geologic context, the combined geophysical methods improve the likelihood of success for tunnel detection. A variable-frequency electromagnetic survey tool was developed in the 1990s as part of tunnel- detection research, and proven at a tunnel test bed near Otay Mesa, CA. Also at the Otay Mesa site, an ERDC-led team installed and tested a prototype passive-seismic fence, a system that can detect machine and impact noise during the tunnel excavation process. This seismic fence concept has strong potential for deterring tunneling in geographic areas where tunnels have been found most frequently and where cultural clutter limits the usefulness of surface geophysical techniques and tunnel detection. Current ERDC tunnel detection efforts (March 2005) are coordinated with the National Geo- Intelligence Agency (NGA, formerly NIMA) to combine electromagnetic and radar methods with emerging technology in microgravimetry. Introduction Open Access - Permission by Author(s) (2005) See Extended description for more information.

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K26-04815

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