Sun-illuminated seafloor topography, Browns Bank, Scotian Shelf, offshore Nova Scotia

During June 1986, two male sperm whales, Physeter macrocephalus, on the Scotian Shelf were tracked by listening for their clicks with a directional hydrophone for periods of 12.5 and 7 h, respectively. Each whale travelled along the edge of the shelf at about 2 kn (3.6 km/h), and one whale, on two occasions at least, dived to the ocean floor. After about 30 min underwater, the whales spent approximately 9 min at the surface breathing. When the whales were visible at the surface, they were silent, except on one occasion when "slow clicking" (mean interclick interval of 4.6 s) was heard from Whale 2. While underwater, most of the sound production consisted of "usual clicks" (mean interclick interval 0.96 and 0.69 s for the two whales) interrupted by frequent short silences (mean durations 21.06 and 27.82 s) and occasional "creaks" (with interclick intervals less than 0.2 s) and "slow clicks." No "codas" (stereotyped patterns of clicks) were heard from these two single whales. These results are consistent with the hypotheses that "usual clicks" and "creaks" are used for echolocation and "codas" for communication.

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Comparison of the S/N ratios of low-frequency hydrophones and geophones as a function of ocean depth

Bulletin of the Seismological Society of America ◽

10.1785/bssa0710051649 ◽

1981 ◽

Vol 71 (5) ◽

pp. 1649-1659

Author(s):

Thomas M. Brocher ◽

Brian T. Iwatake ◽

Joseph F. Gettrust ◽

George H. Sutton ◽

L. Neil Frazer

Keyword(s):

Nova Scotia ◽

Continental Margin ◽

Low Frequency ◽

Weather Conditions ◽

Ocean Bottom ◽

Ocean Bottom Seismometer ◽

Scotian Shelf ◽

Ocean Bottom Seismometers ◽

Particle Velocities ◽

Refraction Data

abstract The pressures and particle velocities of sediment-borne signals were recorded over a 9-day period by an array of telemetered ocean-bottom seismometers positioned on the continental margin off Nova Scotia. The telemetered ocean-bottom seismometer packages, which appear to have been very well coupled to the sediments, contained three orthogonal geophones and a hydrophone. The bandwidth of all sensors was 1 to 30 Hz. Analysis of the refraction data shows that the vertical geophones have the best S/N ratio for the sediment-borne signals at all recording depths (67, 140, and 1301 m) and nearly all ranges. The S/N ratio increases with increasing sensor depth for equivalent weather conditions. Stoneley and Love waves detected on the Scotian shelf (67-m depth) are efficient modes for the propagation of noise.

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