It was a relatively powerful 5.8 magnitude earthquake centered in Virginia. It struck at 1:50 p.m. one year ago on August 23.
Some people in Tredyffrin and Easttown felt it. Others did not.
The shaking was enough to damage the Washington Monument, which remains closed for repairs.
Some local commuters told TE Patch they fled from Center Philadelphia high-rise offices as the streets below were teeming with people.
Where were you when the earthquake hit? Tell us your earthquake story in the comments section at the bottom of this article.
You can also upload photos from that day by clicking the upload photos button.
Here are some of the earthquake stories from TE Patch that day and the next.
(This story includes some pretty cool animation of seismic activity on the continent).