Quick Dips

Electromagnetic Searches for Avalanche Victims

Electromagnetic searching techniques used in geophysical surveys may hold out hope for finding avalanche victims.

Traditionally, rescuers have used probes to prod through fallen snow for buried victims. While this can be successful, it is time-consuming and of little use in large avalanches. The Broken River avalanche, which killed a ski field worker last year, saw 300,000 cubic metres of snow and ice pour over the Broken River field. Some 100,000 tonnes of snow, ice and fine scree buried the area, and attempts to locate the body of the missing worker using probes were unsuccessful.

David Nobes, of Canterbury University's Geology Department, suggested using geophysical survey techniques, involving a horizontal loop electromagnetic (HLEM) system. In the past, this technique has been applied to identify disturbed ground where a body may be buried, rather than the actual body itself, and Nobes believes that this is the first time it has been used to aid a search for an avalanche victim.

HLEM methods could enable the saline fluids of a body to be detected, or could pick up the presence of metal. In the Broken River case, the HLEM search for the body was unsuccessful, but the system did locate parts of the buried tow system. Anomalous electromagnetic readings showed where a 3-mm steel trip line was buried under 2.5 metres of snow. Poor weather and additional snowfalls hampered efforts to use the system, but Nobes remains confident that the avalanche application has potential.