Item: Analysis of the effectiveness of geophysical methods in the locating of snow avalanche victims
Title: Analysis of the effectiveness of geophysical methods in the locating of snow avalanche victims
Proceedings: Proceedings of the 2004 International Snow Science Workshop, Jackson Hole, Wyoming
Authors: D. KLEPACKI, N. J. DIMICK, and M. WENNOGLE, STUDENT, GEOPHYSICAL ENGINEERING, COLORADO SCHOOL OF MINES 1660 Stoney Point Court Colorado Springs, CO 80919, BS GEOPHYSICAL ENGINEERING, COLORADO SCHOOL OF MINES, BS GEOPHYSICAL ENGINEERING, COLORADO
Abstract: Hundreds of people worldwide are killed in snow avalanches each year. (Adkins, CAIC) A small percentage of victims remain missing after the use of traditional techniques including probe lines and cadaver dogs. (Aspen Grove avalanche, 2003) Geophysical methods may provide an effective means by which to locate victims before the summer thaw. Research focused on the locating of metallic debris that could remain attached to a buried victim. Three geophysical tools used in the research include the Geonics EM-31 and EM-61 and a Pulse EKKO 1000 GPR equipped with 450MHz antenna. A survey grid was set up at Loveland Ski Area, Colorado during the winter of 2004. The survey included various backcountry objects commonly accompanying a victim as well as objects known to give false victims indications with geophysical tools. Data suggest that EM-31 and EM-61 tools are not able to uniquely locate single metallic debris and should not be used for victim location unless perhaps the victim is known to be carrying a large amount of metal. The data also suggest GPR can be used to uniquely resolve debris orientation and material composition. GPR was effectively utilized to uniquely identify debris based on material composition and shape. Shape was determined by varying the azimuth of data lines about a target and observing changes in moveout. Material composition was determined through wavelet polarity analysis. GPR data was also collected in April 2004 at the Aspen Grove avalanche site in Provo Canyon, Utah. The purpose of the Aspen Grove survey was to locate the lone remaining victim of the December 26, 2004 Elk Mountain avalanche. Data collection revealed challenges that include the resolving of ice layers, identifying rocks, trees, and ice blocks, determining high-probability targets, and coordinating with the search and rescue team. Both processed and real-time singe-stack data were used in the search, which was performed with cross-line spacing of 3ft and inline flag spacing of 6ft. Trees, rocks, and metallic debris were uniquely identified and classified as low probability targets. One high probability target was identified during the search and remains unidentified. The victim later melted from the snow-pack a short distance from the survey grids; the victim was not imaged in the survey. More than $12,000 and 7000 man-hours were spent searching. (Utah Avalanche Information Center) The time and money spent by Utah County Search and Rescue illustrates the potential for GPR to streamline searches and save valuable time. Aggregate results of the research suggest EM-31 and EM-61 instruments cannot detect single objects commonly carried on the victim while GPR may function effectively when data interpreters are versed in debris identification.
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Keywords: avalanche, victim recovery, ground penetrating radar (gpr), electromagnetic
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