What you’re seeing here are vertical displacement measurements from an array of detectors that are part of the USArray/EarthScope facility (you can read more about the array and the animation on the IRIS website). These are very sensitive instruments; note the scale on the lower graph showing the motion is only about 40 microns top-to-bottom! That’s less than the thickness of a human hair.While most of the national monuments remained intact after the quake, the Washington Monument apparently suffered some damage that was discovered during a secondary survey of the tallest structure in the District of Columbia.
Red dots represent upward motion, and blue downward. The intensity of the color represents the amplitude (height) of the wave. Animations like this make it very easy to see the waves moving across the country; the arc even gives you a rough idea of where the epicenter was.
The National Cathedral also suffered damage and will be closed until further notice.
A window blew out on the Pfizer headquarters in Manhattan, and a chimney partially collapsed on an apartment building in Red Hook, Brooklyn.
Damage was also reported in Tysons Corner, Virginia, where there was a partial wall collapse, damaging a number of cars. Other videos are showing the contents of stores being thrown to the ground and the quake rumbled through.
Although this was a moderate quake, it has a significant reach due to the nature of the geology under the Eastern United States.
In the NYC metro area, some had flashbacks to the reactions of 9/11 - and the need to flee buildings when the rumbling began. But between those who felt the quake and fled, others needed to be told that a quake actually occurred because they didn't feel a thing. I fall in that latter category since I didn't feel it. It was only after others told me that they thought they felt a quake that I went online to the USGS site to learn that a quake occurred - down in Virginia.