ASA 126th Meeting Denver 1993 October 4-8

4pAB5. Vocalizations of blue and fin whales during a midocean ridge airgun experiment.

Mark A. McDonald John A. Hildebrand Spahr Webb LeRoy Dorman

Scripps Inst. of Oceanogr., Univ. of California, La Jolla, CA 92093-0205

Christopher G. Fox

OSU Hatfield Marine Sci. Ctr., Newport, OR 97365-5258

Numerous seismic experiments are conducted each year in the deep oceans to study the nature of oceanic crust and to map the source of seismic signals associated with small earthquakes or volcanic activity. Whale vocalizations of the type associated with blue and fin whales are often recorded on the arrays of seafloor seismometers and hydrophones used for these experiments. These whale vocalizations are characterized from one such experiment conducted about 500-km offshore from Astoria, Oregon in August of 1990. The travel time differences and signal amplitudes from both direct and multipath arrivals across the seafloor seismometer array are used to locate the whales and predict the level of ship and airgun noise at the whale. Whale vocalizations were recorded during airgun operations and these vocalization patterns are compared to patterns recorded during times of relative quiet from the 12 days of data gathered in this experiment. Transient oceanic sound levels from transform fault earthquakes and seafloor volcanic activity are often louder than those produced by airguns.