Broadband sound pressure field characteristics of marine seismic sources used by R/V Polarstern
Single airguns and airgun arrays of different size and volume are used as sound sources for scientific marine seismic reflection and refraction surveys conducted by R/V Polarstern in the Arctic and Antarctic Ocean. To ensure that these research activities do not affect marine wildlife and particular...
| Main Authors: | , , , , , , , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2006
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/14685/ https://hdl.handle.net/10013/epic.24927 |
| Summary: | Single airguns and airgun arrays of different size and volume are used as sound sources for scientific marine seismic reflection and refraction surveys conducted by R/V Polarstern in the Arctic and Antarctic Ocean. To ensure that these research activities do not affect marine wildlife and particularly marine mammals in the Antarctic Treaty Area south of 60°S knowledge of the sound pressure field of the seismic sources is essential. Therefore, a broadband marine seismic source characterization study was conducted at the Heggernes Acoustic Range in the Herdlefjord, Norway in October 2003. The objectives were (1) to determine the spatial distribution of the sound pressure levels emitted by Polarstern's seismic sources, (2) to compute the source levels assuming a spherical amplitude decay, (3) to determine mitigation radii, within which at least some species of marine mammals might possibly experience behavioral or physiological disturbance due to the received sound pressure levels. The thresholds currently in use to determine mitigation radii are 160 dB(RMS) re 1 µPa for potential behavioral disturbance and 180 dB(RMS) re 1 µPa for potential physiological and hearing effects like temporary threshold shifts.To determine the spatial distribution of the sound pressure levels each airgun (array) was shot along a line of 2-3 km length running between 2 hydrophone chains with receivers in 35, 100, 198 and 263 m depth. A GI-Gun (2.4 l), a G-Gun (8.5 l) and a Bolt PAR CT800 (32.8 l) were deployed as single sources, and 3 GI-Guns (7.4 l), 3 G-Guns (25.6 l) and 8 VLF-Guns (24 l) as arrays. The measurements are complemented by a modeling approach for an 8 G-Gun (68.2 l) and 8 G-Gun+1 Bolt PAR CT800 array (100.1 l). The data analysis includes a determination of peak-peak, zero-peak and RMS-amplitudes, sound exposure levels and amplitude spectra as function of source-receiver distance.The amplitude vs distance graphs, analyzed for the 4 hydrophone depths, show the typical directivity of marine seismic sources. Due to the ... |
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