The Richter Scale
Michigan Tech Seismic Education Site
This page provides an introduction to the Richter Scale. Be sure to click on the "table" link to see the magnitude scale.
Earthquakes in South Dakota
This website provides a visual picture of where earthquakes have happened in South Dakota. Click on the three links at the top of the page to see a list of magnitudes, a visual picture of the Richter scale, and comparing the Richter scale to the Mercalli scale.
Purplemath is a website designed with the mission of "helping students gain understanding and self-confidence in algebra."
Toward the bottom of this page, there is a good example of an application word problem using the Richter Scale.