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Seismic Testing

Long before the first drop of oil or gas is extracted from the sea bottom, there is a serious threat from offshore oil and gas development. To begin, seismic tests are conducted to gather information about rock formations and where or not oil or gas might be found. Seismic testing uses air guns that send explosive shock waves into the seabed, which then reverberate through the marine environment. Although the direction of the greatest sound intensity is downward, a considerable amount of energy is radiated horizontally. Seismic testing can be heard many kilometres from the source. For example, the seismic activity off Nova Scotia is heard off the Bahamas, several thousands of kilometres away.

During seismic surveys, high intensity and low frequency sounds are emitted into the marine environment. An array of air guns, which typically include between 15 and 45 air guns, fires shots approximately every ten to 25 seconds, twenty four hours a day. Surveys can last several months and an area of the ocean may have more than one seismic survey performed on it. Seismic testing occurs throughout the entire lifetime the offshore oil and gas industry operates in a particular area. For example, on the east coast of Canada, in the waters off Newfoundland and Labrador, more than one million kilometres of seismic have been shot between 1964 and 2002.

This deafening noise causes fish swim bladders to explode, it kills marine larvae and disrupts the traditional migratory paths of some fish species and marine mammals, such as whales and dolphins. In some places, these disturbances have resulted in reductions in commercial fish catches up to 50 percent, and have caused whales to leave waters where they are habitually found.

The sounds emitted from seismic air guns travel a far distance in the ocean environment. For example, seismic testing that took place off the coast of Cape Breton was recorded in the Bahamas. According to Dr. Chris Clarke, Director of the Bioacoustics Research Program at Cornell University, seismic testing is the modern form of exploratory dynamite, and “the air guns represent the most severe acoustic insult to the marine environment that [he] can imagine short of naval warfare.”

  Read Dr. Clarke’s submission to the hearings on seismic testing in Cape Breton.

Because marine mammals are extremely acoustically sensitive, international concern has grown regarding threats of seismic testing to marine mammals. Evidence suggests high-intensity sound from sonar and air guns leads to strandings and subsequent mortality of beaked whales. Meanwhile, other species of marine mammals have shown a tendency to react to seismic testing. The critically endangered Sakhalin gray whale population in the western North Pacific has been found to react to seismic surveys at distances greater than 30 kilometres, and high levels of seismic surveys in that region seem to have displaced the whales from their critical habitat.

 Read more about the impacts of seismic testing on the Sakhalin gray whale population.

A recent DFO study on the impact of seismic testing on the snow crab found crabs had damaged ovaries and internal organs. Changes were also observed in crab behaviour, while some lost their legs.

 Read the entire DFO study.

For further reading on the impacts of seismic testing check out the reports in our library.

 

"Seismic air guns represent the most severe acoustic insult to the marine environment that I can imagine short of naval warfare.”

- Dr. Chris Clarke, Director of the Bioacoustics Research Program at Cornell University