EDGE WAVE OBSERVATION USING REMOTE SEISMOACOUSTIC SENSING OF ICE EVENTS IN THE ARCTIC

As part of the Office of Naval Research Sea Ice Mechanics Initiative, a real-time monitoring and processing program for acoustic emission fr om ice fracture and ridge-building events was established. A wide-aper ture, horizontal hydrophone array was used in combination with a verti cal line array to record the acoustic signals, which were then passed through a focused beam former for real-time generation of ice seismici ty maps. A number of rapidly deployable geophone arrays were used in a ctive zones to measure the acoustic emissions in the near field for de tailed seismic event analysis. During one such deployment, a highly re gular transient arrival structure was recorded on all sensors located near a major lead, with a transient appearing every 5 s. These data ha ve been processed using frequency-wavenumber analysis to show that the transients correspond to ''edge waves'' propagating forth and back al ong the edges of the lead, with the probable source being a ''stick-sl ip'' mechanical phenomenon toward the ends of the lead.