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The impact of marine seismic air-guns to whale populations

Muhammad Husni Mubarak LubisGeophysics Dept.

Colorado School of Mines

Picture was taken from www.eoearth.org

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Do you know that…?

383 Cetaceans (whale and dolphins) were stranded in the Northern of Gulf of Mexico from November 3, 2010 – Januari 8, 2012. 95 % were found dead. Picture was taken from NOAA

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Do you know that…?

March 2011, 400 pilot whales were found dead along the shore of Speedweel Island, East Falkland Argentina. Photo was taken from http://en.mercopress.com

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can seismic acquisition programs harm and strand the whale populations?

Both area, GOM and Falkland, are really busy with marine seismic exploration activities.

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Research shows that air-gun, the wave source in a marine seismic exploration, can affect the existing whale populations near the survey location (Caldwell, 2000).

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Outline

• Introduction• Sound waves in Seismic Exploration• Sound waves used by Whales• Seismic Exploration Whales• Conclusion

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Sound Waves : Seismic Exploration

Marine Seismic Survey to find oil and gas (www.deafwhale.com)

An air-gun array usually consist of 25 – 100 airguns (www.oceanjsu.com)

5 Hz – 80 Hz Frequency with 242 dB re 1μPa – 1m of intensity level (Landrø

and Amundsen, 2011)

The seismic energy dissipates with distance

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Sound waves : Whales

Whale sound producing mechanism from Scheifele (1991), picture was taken from www.dosits.org

Whale produces and receives sound waves from www.seaworld.org

Low Frequency – 10 KHz Frequency (Gausland, 2000) with

236 dB re 1μPa – 1m of intensity level (Møhl et al., 2000)

Whales use sound waves to :- Communicate- Sense- Find food- Navigate

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Seismic Exploration Whales

The marine mammals’ audiogram coincide with the seismic spectrum. From

www.subacoustech.com

Due to the coincidence of whales’ audiogram with seismic airgun bandwidth, behavioral change can happen. (Gausland, 2000).

Behavioral changes are the swimming direction (from Gary Isaksen’s (ExxonMobil) Presentation).

The change is temporal and localized due to the nature of seismic shot.

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Seismic Exploration Whales

Whales and air-gun use similar sound pressure/intensity level. That’s why it will not harm the whales. From usgs.gov

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Conclusions

• The air-gun used in a seismic survey affects the local population of whales by changing their behaviors, swimming direction, temporally. No permanent effect like hearing lost, physical injuries etc.

• Although data show that the seismic waves generated by the air-gun do not cause any hearing problems and physical injuries, the stranding of whales still become a mystery.

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Sources• Lasse Amundsen and Martin Landrø, “Marine Seismic Sources Part IV”, 2010. Retrieved January 16, 2012, from

http://www.geoexpro.com/article/Marine_Seismic_Sources_Part_IV/e475fb6e.aspx • USGS, “Airgun and Source” Retrieved January 16, 2012 from http://walrus.wr.usgs.gov/earthquakes/ships/airgun.html • Discovery of Sounds in the Sea, “Animals and Sound” Retrieved January 16, 2012 from

http://www.dosits.org/animals/animalsandsoundsummary/

• NOAA, “2010 – 2012 Cetacean Unusual Mortality Event in Northern Gulf of Mexico” Retrieved January 16, 2012 from http://www.nmfs.noaa.gov/pr/health/mmume/cetacean_gulfofmexico2010.htm

• MercoPress, “Falklands reports grounding of a pod of 400 pilot whales”, March 19, 2011. Retrieved from http://en.mercopress.com/2011/03/19/falklands-reports-grounding-of-a-pod-of-400-pilot-whales

• Ingebret Gausland, “Impact of seismic surveys on marine life”, August 2000. Retrieved from • http://library.seg.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=LEEDFF000019000008000903000001&idtype=cvi

ps

• Jack Caldwell, “Does air-gun noise harm marine mammals?”, August 2000. Retrieved from http://library.seg.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=LEEDFF000021000001000075000001&idtype=cvips

• Bill Dragoset, “Introduction to airguns and air-gun-array”, August 2000. Retrieved from http://library.seg.org/getpdf/servlet/GetPDFServlet? filetype=pdf&id=LEEDFF000019000008000892000001&idtype=cvips

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Thank You

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