Felt Anything Odd Lately?

SignOnSanDiego.com > News > Metro -- Mystery disturbance traced to sound wave:

"According to data analyzed by the scientists, the wave was felt on San Nicolas Island, northwest of San Clemente Island, at 8:40 a.m. It hit Solana Beach at 8:46 a.m., the western edge of the Cleveland National Forest at 8:47.30 and the eastern side of the Salton Sea at 8:53 a.m. From there, it appears to have dissipated.

Elizabeth Cochran, the lead researcher on the project, said the wave moved at 320 meters per second, roughly the speed that sound travels through the air. Its velocity was too slow to be that of an earthquake, she said.

Cochran, a postdoctoral researcher in the geophysics and planetary physics department, said the only explanation is that the wave was traveling through the atmosphere, not through the ground. At each location, the wave could be felt for roughly 10 seconds, she said.

Several months before the April 4 incident, the team had begun studying other nonquake disturbances that were registering on San Diego County seismometers, including 76 that apparently originated in that same general area of the ocean in 2003. Shearer said he and his colleagues figured that some of those disturbances surely must have come from offshore military exercises.

The researchers haven't been able to determine whether the April 4 wave was more powerful than the earlier ones or whether it simply felt that way because of atmospheric conditions.

If the disturbance was caused by the military, no one has owned up to it. The Navy and Marines say none of their planes were flying at supersonic speeds that morning.

“I'm told that a sonic boom would not cover that distance at all,” said Fiebing, the Navy spokesman.

The Navy uses Warning Area 291 for a wide range of training, including large-scale ship maneuvers and battle exercises, but Fiebing and Fenick said they were unaware of any such training April 4 that would have caused such a disturbance.

Authorities have said a meteor probably wasn't the cause because it would have been noticed by the scientific community. The American Meteor Society reported no fireball sightings over Southern California on that day.