Seismic Survey Dangers
A seismic survey involves the use of sound waves bounced off the ocean's floor or sent underground. Its purpose is to gather information about the composition and structure of the seabed; identify sources of oil and gas deposits under the ocean and underground and find sources of water. Underground seismic surveys create dangers to the Earth's stability while undersea surveys harm marine life and impact the fishing industry.
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Explosives
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One type of underground seismic survey for petroleum reserves requires a hole to be dug, known as a shot hole. Explosives provide the means to create the hole. Dangers from this technique include underground rocks cracking and damaging the water table. Explosions too close to a building's foundation or a water well can result in damage. Following completion of the seismic survey, the hole must be filled up or contaminants can enter the underground rock layers or water table.
Vibrations
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Underground seismic surveys produce vibrations. The amount of the vibrations depends upon the soil and rock type, depth of the survey and the intended source according to the Utah Geological Survey. The deeper the survey, the more intense the vibrations. Staying clear of the survey area avoids most of the dangers from vibrations. The earth does move but sufficient distance provides protection.
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Ocean Noise
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Seismic surveys in the ocean generate considerable noise. The typical survey lasts two to three weeks and covers 300 to 600 miles producing sounds in the range of 250 decibels, or dB. Levels up to 117 dB can be heard over 20 miles underwater according to the Alaska Marine Conservation Council. For comparison, human ears suffer damage at 120 dB. Marine life such as whales and dolphins rely on sound rather than sight for navigation and communication. These surveys disrupt their normal migration patterns causing them to avoid areas of seismic surveys. Extended exposure to seismic surveys results in permanent damage.
Damage to Fishing Industry
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The noise from seismic survey results in fish-kills and reduced numbers of fish. The Alaska Marine Conservation Council details the impact of the fishing industry. Most surveys occur in the summer and coincide with prime fishing season. Commercial fishermen in Alaska report diminished catch rates of up to 78 percent over short periods of time during seismic surveys.
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References
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