By the way, did you know we haven't been using the Richter Scale since 2002? CLICK HERE to find out more.
Here's another resource, posted by Mark Colberg, Associate Prof. of Geol. at Southern Utah University. Colberg's web page outlines the basic principles of earthquakes and provides links to the best animations of seismic waves that I've seen. CLICK HERE to view the page and then scroll down to access the animations.