Delaware earthquake shakes Philly region

If you felt a random little rumble this afternoon, you’re not alone or going crazy: The Philly region felt the effects of a 4.1 magnitude earthquake that took place near Dover, Delaware.

The United States Geological Survey reported that the earthquake took place at 4:47 p.m. about six miles northeast of Dover. But based on reactions around the Twitterverse, the shakes from the earthquake were felt by folks all around the region, including right in Center City, Philadelphia.

At first, the USGS reported a 5.1 magnitude earthquake, then soon revised it to 4.1.

To state the obvious, East Coast earthquakes are not a common occurrence. The last major earthquake that occurred in this region took place in 2011 in Virginia. That one clocked in at 5.8 magnitude and was felt up and down the coast.

Here’s what the USGS had to say about East Coast earthquakes:

Most of North America east of the Rocky Mountains has infrequent earthquakes. Here and there earthquakes are more numerous, for example in the New Madrid seismic zone centered on southeastern Missouri, in the Charlevoix-Kamouraska seismic zone of eastern Quebec, in New England, in the New York - Philadelphia - Wilmington urban corridor, and elsewhere. However, most of the enormous region from the Rockies to the Atlantic can go years without an earthquake large enough to be felt, and several U.S. states have never reported a damaging earthquake.

Scientists who study eastern and central North America earthquakes often work from the hypothesis that modern earthquakes occur as the result of slip on preexisting faults that were formed in earlier geologic eras and that have been reactivated under the current stress conditions. The bedrock of Eastern North America is, however, laced with faults that were active in earlier geologic eras, and few of these faults are known to have been active in the current geologic era.

There have been no reports yet of injuries or damage from the earthquake’s epicenter in Dover. The Philadelphia Office of Emergency Management also confirmed that there have been no reports in Philly, either.

Here are some early reactions from folks who felt the rumble: