Wednesday, December 23, 2009
Skyquakes: They're back!
Mysterious boom shakes county
A mysterious boom that rattled buildings was reported Monday afternoon from as far north as Poway to as far south as Chula Vista, authorities said.
Calls began pouring in to 911 dispatch centers about 4 p.m., with people asking if there had been a massive explosion or if an earthquake had struck, said Maurice Luque, spokesman for the San Diego Fire-Rescue Department.
Neither was the case.
Civilian authorities reached out to local military bases to see if they could shed any light, and they were just as puzzled as everyone else, Luque said.
The disturbance was so intense in some areas that firefighters at a station in Clairemont evacuated the building and moved the fire engines out of the garage, thinking it was an earthquake, Luque said.
Mysterious booms have been reported previously in San Diego County, with one of the last major ones reported the morning of April 4, 2006.
Later that month, scientists at Scripps Institution of Oceanography in La Jolla said the disturbance was a sound wave that started in the Pacific Ocean and reached the Imperial County desert. Using data from more than two dozen seismometers, they traced its likely origin to a spot roughly 120 miles west of the San Diego coast frequently used for military training.
Military officials said there were no exercises in the area at the time of the boom.
San Diego earthquake mystery solved?
Today, residents of San Diego felt the familiar shake of the ground and heard a loud, thundering noise. Many assumed that another San Diego earthquake was underway. The mystery ensued as the United States Geological Survey began to investigate the matter.
After several hours, seismologists worked the case and determined that the loud noise was not an earthquake but rather a sonic boom. According to USGS seismologist Robert Dollar spoke with channel 10 news and stated that military high speed air craft were most likely the culprits.
A similar incident occurred on April 4, 2006 in San Diego County.
LINK TO LIST OF USGS TREMORS on December, 21, 2009.
Note: the series of tremors starting at 15:12 (3:12 PM) and ending at 15:48 PM
(when the loudest booms were reported) indicate several USGS sensor recording a series of small tremblors (magniitude 0.3 and above) at slightly different times and locations, from Pinnacles to Alum Rock to Parkfield California.