NEW ORLEANS mdash; The U.S. Geological Survey says an earthquake of magnitude 3.9 occurred late Sunday at a point about 175 miles south-southeast of New Orleans.The temblor occurred about 2 weeks after anbsp;series of earthquakes in northern Louisiana. Scientists speculated that high-pressure injec tion wells may have caused those quakes.Given the location of Sunday's earthquake mdash; halfway between the mouth of the Mississippi River and the Yucatan peninsula mdash; it was unlikely that anyone felt shaking on dry land,nbsp;data on file at the USGS websitenbsp;showed.The United States Geological Survey said the magnitude 3.9 quake struck around 9:22 p.m. at a depth of about 10 kilometers.nbsp;Two weeks ago, a magnitude 4.9 earthquake occurred near Edgefield.nbsp; Several aftershocks occurred in the following days, including a magnitude 4.0 quake near Coushatta.While researchers are still working to determine the exact cause, some advocates believe human activity could be playing a role.Louisiana sits in the middle of the North American tectonic plate, meaning it is not typically an area with active plate movement. However, scientists say there is an ancient fault system beneath the state that could have been disturbed.Permalink| Comments ...read more read less