The greatest threat to America is not from foreign invasion or even attack, but natural disasters, because while the former can be controlled or mitigated as the US is proportionately isolated from the rest of the world, she cannot escape nature, and given the way supply lines are set up, a small disruption could cause a major mess. Thus it is not without surprise but something to note that Virginia this morning had a 2.7 magnitude strong earthquake.
The United States Geological Survey reported a 2.7 magnitude earthquake Monday morning in Virginia.
The quake was reported about 5 miles south of Louisa in central Virginia around 5 a.m. Monday.
According to the USGS website, over 100 reports from people who felt the quake were reported. Most were in and around the Louisa area but tremors were also reportedly felt in the Culpeper and Richmond areas. No damage has been reported. Louisa is about 100 miles south of Washington, D.C. (source)