On August 23, 2011 a 5.8 earthquake emanated from the little-known Central Virginia Seismic Zone. The epicenter was near Mineral, VA, but the tremor shook homes, schools, and office buildings in Washington, DC, including Smithsonian Institution buildings, and beyond. In this brief video, Smithsonian educator Catherine Sutera uses a Slinky® to demonstrate two types of seismic waves that people in the area may have felt: the P wave and the S wave. Both are known as "body waves," because they move through Earth's interior. The P wave, also called the primary wave, is the fastest seismic wave. But it's the S wave that creates much of the above-ground shaking during an earthquake. You can learn more about body waves and the more complicated surface waves on Michigan Tech's Geological and Mining Engineering and Sciences website. Want more specifics on the Virginia earthquake? Smithsonian geologist Elizabeth Cottrell answers the main questions on Smithsonian Magazine's website.