The U.S. Geological Survey says a strong magnitude 6.0 earthquake in the Gulf of Mexico sent shockwaves from Louisiana to southwest Florida, but no damage has been reported.
The agency says the earthquake was centered about 260 miles southwest of Tampa and about 250 miles south-southwest of Apalachicola.
The quake came from about 6.2 miles below the Gulf surface, but it was too small to trigger tsunami danger, and USGS geophysicists say there is, right now, no reported damage to oil rigs in the Gulf.
The USGS received almost 1,500 reports from people as far away as North Carolina who felt the 10:56 a.m. Eastern temblor.
Media reports from Tampa say residents reported feeling their buildings vibrate for up to 20 seconds.
The epicenter is an unusual location for earthquake activity, but scientists recorded a magnitude 5.2 temblor in the same location on February 10.
Quakes in the Gulf are infrequent, but Sunday morning's was the largest of more than a dozen shocks that have been recorded in the area in the past 30 years.
USGS geophysicists say the quake area is not located on a geological fault but rather in the middle of the North American plate.
They say earthquakes could be caused by the release of long-term stress under the plate.