ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

3aUW4. Acoustic and seismic measurement of ice processes.

David M. Farmer

Yunbo Xie

Inst. of Ocean Sci., P.O. Box 6000, Sidney, BC V8L 4B2, Canada

As sea ice responds to environmental forcing, it deforms leading to the storage of strain energy. When mechanical failure occurs, most of this energy is dissipated through fracturing, but a small portion radiates as seismic and acoustic waves. These waves provide useful signals for sensing the failure process in the ice. In a recent ice mechanics experiment conducted north of Prudhoe Bay (SIMI '94), a large number of ice failure events were observed using geophone and hydrophone arrays. Preliminary results are presented, including a large-scale tensile fracture test and naturally occurring sounds near a closing lead. For the artificial fracture, the acoustic signals allow determination of cracking rate, fracture advance, and crack propagation velocities. The overall crack propagation speed is estimated to be of order 50 m s[sup -1]; maximum cracking activities occur prior to peak loading. In the second data set, the naturally occurring stick-slip process was observed as two ice sheets moved against each other in a closing lead. A wide range of frequencies can occur simultaneously representing different components of the sliding and slipping mechanisms.