A rare 4.1 magnitude earthquake struck Dover, Delaware today, with reports of shaking from Maryland to New York.
The United States Geological Survey reported the earthquake, which struck at 4:47 PM local time. The earthquake epicenter was centered 6 miles to the northeast of Dover Delaware. The earthquake shook several states on the east coast of the United States that aren't used to experiencing earthquakes in this geologically stable part of the world.
There are no current reports of injuries or damages to infrastructure or buildings. In addition, there is no risk of a tsunami as the earthquake was centered over land and hence didn't thrust ocean water upward. Likely the extent of damage will be items falling off shelves and some cracks in drywall.
As the quake hit, people in downtown Dover went outside to see what was happening, not initially realizing they were experiencing an earthquake in Delaware. The earthquake's epicenter lies just 50 miles from Philadelphia, Pennsylvania, 65 miles from the city of Baltimore, Maryland, 90 miles from Washington, D.C. and approximately 125 miles from New York City. Surprisingly, the earthquake tremors traveled a significant distance and were felt over a hundred miles away from the source.
The earthquake focus (origin of the earthquake) was 5 miles deep and was located in a region not prone to earthquakes. The east coast of the United States lies on a passive margin and thus does not frequently experience tectonism. This part of the world rarely experiences earthquakes and people can go many years without feeling a tremor.
When earthquakes do occur, however, it is a result of faulting in the underlying bedrock formations. These can sometimes occur on undocumented relict fault lines that haven't been for millions of years. In addition, there is no evidence noted by the USGS that links this earthquake to human-induced seismicity.
While this earthquake in Delaware was surprising, it is unlikely to happen often in this geologically stable region. Every once in a while the east coast experiences an earthquake and thankfully they are rarely damaging. However, in August of 2011, a 5.8 magnitude earthquake struck Virgina, which produced cracks in the Washington Monument and damaged 3 of the 4 spires in the Washington National Cathedral.
