image credit: USGS; image source; larger image
Understanding Plate Motions
This map, from a USGS poster, shows the epicenter of the May 12 earthquake in Sichuan, China, along with the boundary, at the lower left, between the India Plate and the Eurasian Plate. The northward movement of the India plate produces the frequent seismic activity in China. For a satellite view of the earthquake region, see this Earth Observatory image. For the theory of the movements of plates in the Earth's crust, visit the USGS' Understanding Plate Motions.
Visit the Exploratorium's Faultline for a general introduction to earthquakes, with data, photos, activities, and more. Also, check out Plate Tectonics for plate tectonic animations, along with a description of the theory and how it was developed.