ST. AUGUSTINE BEACH, Fla. - Opening the Eastern Seaboard to offshore oil exploration for the first time in decades, the Obama administration on Friday approved the use of sonic cannons to discover deposits under the ocean floor by shooting sound waves 100 times louder than a jet engine through waters shared by endangered whales and turtles.

The U.S. Bureau of Ocean Energy Management's approval of this technology is the first step toward identifying new oil and gas deposits in federal waters from Florida to Delaware.

The sonic cannons are towed behind boats and emit strong pulses of sound every 10 seconds or so, reverberating beneath the sea floor and bouncing back to the surface, where they are measured by hydrophones. Computers then translate the data into high resolution, three-dimensional images.

"It's like a sonogram of the earth," said Andy Radford, a petroleum engineer at the American Petroleum Institute, an oil and gas trade association in Washington DC. "You can't see the oil and gas, but you can see the structures in the earth that might hold oil and gas."

The sonic cannons can be fired consistently for weeks or months depending on the project, and pose real dangers for whales, fish and sea turtles that also use sound to communicate across hundreds of miles. In an environmental impact study of the project, the U.S. government estimates that more than 138,000 sea creatures could be harmed.

Of foremost concern are endangered species like the north Atlantic right whale, with a total population of about 500. The whales use the seas off of northern Florida and southern Georgia to give birth to their calves before their migration north. Since the cetaceans are so scarce, any impact from this intense noise pollution on feeding or communications could have long-term effects, Scott Kraus, a right whale expert at the John H. Prescott Marine Laboratory in Boston, said.

"No one has been allowed to test anything like this on right whales," Kraus said of the seismic cannons. "(The Obama administration) has authorized a giant experiment on right whales that this country would never allow researchers to do."