HR: 1330h
AN: OS42A-0830    [PDF]
TI: Seismic airgun sounds recorded on moored hydrophones near the Mid-Atlantic Ridge and East Pacific Rise
AU: Mellinger, D K
EM: david.k.mellinger@noaa.gov
AF: Cooperative Institute for Marine Resources Studies/ Oregon State University, 2030 SE Marine Science Dr., Newport, OR 97365 United States
AU: Nieukirk, S L
EM: sharon.nieukirk@noaa.gov
AF: Cooperative Institute for Marine Resources Studies/ Oregon State University, 2030 SE Marine Science Dr., Newport, OR 97365 United States
AU: * Dziak, R P
EM: robert.p.dziak@noaa.gov
AF: Cooperative Institute for Marine Resources Studies/ Oregon State University, 2030 SE Marine Science Dr., Newport, OR 97365 United States
AU: Haxel, J H
EM: joe.haxel@noaa.gov
AF: Cooperative Institute for Marine Resources Studies/ Oregon State University, 2030 SE Marine Science Dr., Newport, OR 97365 United States
AU: Fox, C G
EM: christopher.g.fox@noaa.gov
AF: Pacific Marine Environmental Laboratory National Oceanographic and Atmospheric Administration, 2115 SE OSU Drive, Newport, OR 97365 United States
AB: Sounds of seismic airguns were detected in two years of data collected from large, remote areas near the Mid-Atlantic Ridge (MAR) and the East Pacific Rise (EPR). From February 1999-February 2001, six autonomous hydrophones were moored near the MAR between 15-35 N and 33-50 W, and six more were moored in the EPR between 8 N - 8 S and 95-110 W. Continuous acoustic data recovered from both arrays were examined for sounds associated with seismic airgun activity. This was done using an automatic detection algorithm designed to identify repetitive sounds in the 20-60 Hz band. Airgun impulses occurred every 10-20 s and were recorded frequently on all hydrophones. In the Atlantic, airgun activity peaked in the summer months, and airgun impulses were detected in nearly 100% of the hours examined; Pacific seasonal trends were less obvious. Because of the high source level of the airgun signals, it was possible to estimate the locations of ships conducting seismic surveys despite their great distance, often over 3,000 km from our array. In the Atlantic, we located seismic vessels, presumably commercial, working off the coast of Nova Scotia during summer, and off western Africa and northeast Brazil in spring, summer,and fall. During summer 1999, research airguns were recorded on the MAR near 26 N 50 W. In the eastern tropical Pacific, the predominant source of airgun sounds was seismic vessels in the nearshore waters of southern Ecuador and northern Peru. All of the areas in which intense airgun activity was detected include important habitat for marine mammals; one area included habitat of the critically endangered northern right whale. Sounds from airguns appear to be a major contributor to the sound field in the Atlantic and parts of the Pacific Ocean, and may be of concern given the recent interest in ocean noise and its effects on marine mammals. Acoustic pressure levels of earthquakes are also investigated, and received levels in some common marine mammal habitats are calculated. It is hoped that these data will provide the marine mammal community with insight into the major components of the marine noise field.
DE: 3025 Marine seismics (0935)
DE: 3094 Instruments and techniques
DE: 4259 Ocean acoustics
DE: 4830 Higher marine organisms
SC: Ocean Sciences [OS]
MN: 2003 Fall Meeting