13 March 2005.

A writes:

Such mystery booms have a very long history and have been reported from all over the world.  Sometimes a cause can be identified, but mostly they remain a mystery.

http://www.lewis-clark.org/content/content-article.asp?ArticleID=1217

http://www.du.edu/~jcalvert/waves/barisal.htm

http://www.unknowncountry.com/news/?id=4275

Et multiple cetera.

The 1977 MITRE book by Claflin-Chalton and MacDonald, "Sound and Light Phenomena: a Study of Historical and Modern Occurrences" is probably the best single reference for such things.

12 March 2005.

F writes:

I experienced something similar in 2003 here in Charleston SC; don't recall it "lasting" any duration, it was more like a very LARGE sonic boom.  I did a bit of research at that time and there is something referred to as "sky-quakes" that are possibly related to even relatively minor seismic activity.

I AM NOT convinced F-18s (or other similar sized aircraft) could ever cause this type of noise.  Those little lawn-darts generate a rather sharp "crack" vice "boom".  I do remember the twin boom of a Shuttle approach over Jacksonville FL and that event was rather weak compared to the Charleston event and suspect the Tampa event is of related origin.....whatever the hell it is. The following link is to one of the articles in the Portland and Courier archives:

http://archives.postandcourier.com/archive/arch03/0203/arc0207984948.shtml

A report on a similar event in India:

http://cities.expressindia.com/fullstory.php?newsid=120897

News reports of the Florida event:

http://www.sptimes.com/2005/03/12/Tampabay/Sonic_booms_shake_up_.shtml

http://news.tbo.com/news/MGBJICTD76E.html

http://www.bradenton.com/mld/bradenton/news/local/11116217.htm

12 March 2005

M. writes:

Last night the USGS recorded an earthquake of unknown magnitude centered 2 km south of Tampa FL.  The FAA was reported as saying this was a sonic boom cased by two F-18 fighter jets approaching MacDill AFB in Tampa. Anyone who has heard a sonic boom before (and living in Florida, we hear quite a few of them between the space shuttle landings and various military bases) will tell you what happened last night was much more than that.

At 7:41 pm EST, my 3-year old son and I were sitting on the couch when our sliding glass doors started to rattle. 10 seconds later the floor started vibrating, enough to send my son into a panic and inquire what was happening. Having been in earthquakes before, I assumed that's what it was. The entire event lasted about 30 seconds, and was felt in several surrounding counties. A sonic boom, no matter what creates it, is never more than a few seconds. I do not recall hearing the classic "thud" that accompanies the subsonic vibration, but I may have missed it...but the vibration lasted a good 25-30 seconds, and was severe enough to register on local seismic monitoring stations. You can varify the event at earthquake.usgs.gov.

Seeing as how the Air Force alerted the FAA with an explanation, you can probably deduce that this was some sort of military test and the F-18 sonic boom was the cover story. The event was reported in at least 8 surrounding counties, which is an area of a few hundred miles. Sonic booms are never heard or felt over an area that large, even when the space shuttle returns from orbit. Whatever it was, the military isn't giving us the full story, and as usual, the media is doing very little to find out what the real facts are. The Air Force spokesman was quoted as saying the jets would be departing either today or Sunday for the return trip, indicating we may have another "sonic boom".

http://earthquake.usgs.gov/recenteqsUS/Quakes/usvnab.htm

_____

http://earthquake.usgs.gov/recenteqsUS/Maps/US2/27.29.-83.-81.map

An earthquake occurred at 00:41:55 (UTC) on Saturday, March 12, 2005. The magnitude ? (uncertain or not yet determined) event has been located in FLORIDA PENINSULA. (This event has been reviewed by a seismologist.)