Headlines across Florida a week ago declared an earthquake rocked the floor of the Atlantic Ocean just over 150 miles off the coast.

The blast registered as a 3.7 on the Richter scale and was described as a rarity for the Florida coast.

But it wasn't an earthquake.

The U.S. Navy provided the motion in the ocean July 16 as part of a testing program for its state-of-the-art littoral combat ships.

"Each test is conducted with a 10,000-pound charge," said Capt. Thurraya S. Kent, a spokeswoman for the Navy. "Details on specific tests are classified."

It was the final of three tests designed to validate the operational survivability for the USS Jackson - a new ship based at Mayport Naval Station.

The Navy is careful about when the Full Ship Shock Trials take place because of concerns over sea life and other vessels in the water, said Matt Leonard of Naval Systems Command.

Leonard said the Navy sends notices to mariners before each test to be sure the area is clear, due to the hazardous conditions that follow the blasts.

Some believe the Navy isn't vocal enough about when and where they are doing tests similar to the one July 16, said John Hocevar, oceans campaign director for Green Peace.

"You don't want to hear about this by having a seismic indication that they've already blown something up," Hocevar said Friday.

He suggested having public hearings to determine when and where a blast would take place.

Kent said the Navy gets approval from several environmental organizations and takes the safety of animals into consideration as well.

"The Navy takes the safety and security of marine mammals seriously, and all testing keeps in mind the various migration patterns of marine life," Kent said. "Additional lookouts are posted to detect any marine mammal activity and test shots are not conducted if marine mammals are in proximity. Also, a veterinarian is on site."

Kate Brogan, a spokeswoman for the National Oceanic and Atmospheric Administration, backed up that statement.

"Several types and teams of observers are present during each round of shock testing to make sure that no protected species (marine mammals or sea turtles) or important environmental features (such as Sargassum rafts or flocks of seabirds) are in the geographic area where the trial will be occurring," Brogan said in an email.

"No animals have been observed harmed in this round of ship shock trials or in previous trials."

Beth Pike is a conservation scientist with the Marine Conservation Institute, and she said she believes the Navy does everything it can to ensure the safety of animals.

"These things tend to get a lot of attention because it's dramatic," Pike said. "But the bigger problem is not these one-off issues but rather the accumulation of background ocean noise."

Pike said while some fish and other non-migratory animals are always going to be affected by underwater explosions, the bigger problem is chronic man-made noise in the water.

She said there was a noticeable change in marine life after the Sept. 11 attacks, when all air and sea traffic was halted.

Whale researchers collected fecal matter in the Bay of Fundy and found the absence of ships in the water benefited the animals.

"What they realized was that there was a dramatic decrease in the stress hormones of the whales during that time," she said.

Hocevar of Green Peace said no matter how many efforts are made by the Navy to avoid harming the whale population, explosions still have an impact.

The problem is it's impossible to determine for sure whether a test blast directly contributed to the death of a whale, he said.

Hocevar said explosions such as the one off the coast of Florida can leave a whale with severe hearing problems, and deaf whales are often found washed up on shore.

"A deaf whale is a dead whale," Hocevar said because of the importance hearing plays in its survival.

He also said there are other factors that can cause a whale to lose its hearing, making it hard to point the finger of blame at the Navy.

Kent said the Navy will continue these types of tests this summer.

Joe Daraskevich: (904) 359-4308