Opening the Atlantic Outer Continental Shelf to geophysical activities represents a unique opportunity for the nation to assess available resources and to do it in an environmentally responsible manner ("Some Md. lawmakers oppose seismic testing," Aug. 4). Seismic survey activities are temporary and transitory and are the least intrusive way to explore the earth's geology and its dynamic processes. Seismic surveys provide the needed information about the value and location of key resources, enabling the government to evaluate the information and make informed decisions.

Seismic surveys reduce the overall environmental footprint of oil and gas exploration by providing high-resolution data that allow fewer wells to be drilled and maximize production in mature producing fields.


Modern seismic surveys are like ultrasound technology — a non-invasive mapping technique built upon the simple sound wave. The energy source is typically an array of different sized air-chambers filled with compressed air that creates seismic pulses. The source is towed behind a survey vessel and releases bursts of high pressure energy into the water. The pulses bounce off the layers of rock beneath the ocean floor and are picked up by hydrophones pulled behind the survey ship. Seismologists then analyze the information, using computers, to visualize the features that make up the underground structure of the ocean floor.

Contrary to what is being said, seismic air pulses are not "sonic cannons." This erroneously applied term gives the wrong impression that seismic source arrays are destructive to marine mammals and marine life. This is not the case. The seismic air source array is engineered to direct its energy downward and is predominantly low frequency, below the hearing range of many marine species. There is no evidence of serious harm from exposure to seismic air pulses.

Several organizations historically opposed to domestic oil and natural gas exploration and production are engaged in an ongoing campaign, disseminating information that is not always accurate, with the sole intention of influencing public opinion against seismic surveys and persuading the federal government to not permit seismic surveys. Allegations against seismic surveys by the advocacy groups are unfounded and meant to stop future offshore oil and gas exploration and development.

The administration advocates an "all-of-the-above" approach to U.S. energy. Seismic surveys are not only used for oil and gas exploration but also for ground water management, geologic hazard identification and monitoring, engineering studies of roads and other structures and yes, even siting renewable energy projects.

The one thing the industry and the advocacy community share is care and concern for marine life. Environmental stewardship is an industry value and priority. The industry employs measures that are overseen by the government to protect marine life. The industry also funds independent research to further understanding of potential effects of seismic surveys on marine life and to foster new mitigation and monitoring technologies.

Forty years of global experience has demonstrated that seismic survey activities, fishing, tourism and marine life can and do coexist successfully. We encourage the public to find out more about seismic surveys and then make their own judgment based on the facts and reality.

Robert Hobbs, Houston

The writer is chairman of the board of the International Association of Geophysical Contractors.


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