This afternoon the US Geological Survey reported a 3.9 magnitude earthquake off the Atlantic Coast.
The explosion and subsequent quake is currently thought to have been triggered by a US Navy ‘shock test’, similar to what was performed last month when the Navy set off a 40,000 lb explosion in a similar location that also sparked a similar sized quake.
Here is the video from the Navy’s explosion last month that caused a similar sized earthquake in the Atlantic: