Here are some useful places on the internet to learn more about Earthquakes.
Earthquakes on Wikipedia
http://en.wikipedia.org/wiki/Earthquake
A History of Great Earthquakes
http://www.pdc.org/iweb/earthquake_history.jsp
Understanding Earthquakes
http://www.crustal.ucsb.edu/ics/understanding
World-Wide Earthquake Locator
http://tsunami.geo.ed.ac.uk/local-bin/quakes/mapscript/home.pl
The US Geological Survey Site
http://www.usgs.gov/