海角大神

Floridians startled by a distant vibration on Saturday received another surprise on Monday, when the US Navy "confessed" to causing the vibrations with an "experimental explosion."

The 3.7 magnitude seismic event was听initially thought to be caused by a tectonic process, possibly the result of thermal relaxation, or 听that opened the Atlantic Ocean starting about 180 million years ago, as听Ray Russo, associate professor of Geological Sciences at the University of Florida, told First Coast News Monday.

The U.S. Geological Survey has since recategorized the event as an "experimental explosion," after it was informed of the Navy's months-long testing by a member of the press, and the Navy confirmed its activity. Paul Earle, seismologist for the USGS, emphasizes that the event is no longer considered an earthquake in an phone interview with 海角大神.听The Navy is expected to , Dale Eng, a public information officer for听the Navy鈥檚 Sea Systems Command in Washington, told The Daytona Beach News-Journal.

鈥淚鈥檓 interested that the Navy is releasing a statement," Dr. Russo tells 海角大神, as this is the first official Navy statement about testing he has heard about in his decades of research in Florida.

Unlike in North Korea, where test explosions have magnitudes of 4 to 5 and are easily detected by South Korean stations nearby, Russo says, the sources of vibrations off the Florida coast are not easily identified.

This is the second 3.7 magnitude seismic event in two months that has been confirmed as off the east coast of Florida. Both were about 100 miles east north-east of the coast, the first off of Flagler Beach, and this most recent听off Daytona Beach.

The tremors have been caused by testing of the USS Jackson. On June 10, the littoral combat ship endured a 10,000-lb. explosive charge, in the first of a intended to assess the ship鈥檚 resilience.

After seismographs first detected activity in June, the USGS categorized the event as an earthquake, but the Navy this week claimed responsibility for that explosion as well.

When Bruce Presgrave, a geophysicist and shift supervisor at the Geological Survey鈥檚 National Earthquake Information Center in Colorado, saw a photo of the June 10 shock trial, he told News-Journal, 鈥淭hat鈥檚 a , isn鈥檛 it?鈥�

A large underwater explosion 鈥渨ould almost certainly be detected as an earthquake,鈥� he told News-Journal.

Florida does not have a history of devastating earthquakes. In Florida鈥檚 recorded history, only one quake, in 1879,听, according to the USGS.

鈥淓very once in awhile there is a big earthquake, but we don鈥檛 really know the reason,鈥� says Russo. Seismic activity on the US Atlantic coast is usually caused by mantle heating of the crust, he says. When the crust cools, it fractures into faults. Mapping the faults would take too much energy and money, Russo says.

The consequences of explosions such as these are small. Only the Saturday earthquake, according to First Coast News. Mr. Earle says he doesn鈥檛 see the possibility for damage in routine tests like these. 鈥淚鈥檓 sure they took the precautions鈥� to make sure no damage was done, he says.

Professor Russo hopes the Navy will let the USGS and researchers know about explosions in the future. 鈥淲e could use these data,鈥� he says.

Editor's Note: This story has been updated to correct the full name and location of the U.S. Geological Survey and its National Earthquake Information Center.听