The largest quakes ever recorded are about magnitude 8.6. Also, the amount of energy released in the earthquake increases by a factor of about thirty with each digit increase of the Richter magnitude. So an earthquake of magnitude 6.0 releases about 900 times more energy than an earthquake of Richter magnitude 4.0. Tsunami Earthquakes can occur on the sea floor. The rapid movement of such a large body of water generates sea waves of tremendous energy called tsunami .
Tsunami can cause extensive damage in coastal regions.
For more information on earthquake hazards and preparedness, visit this page provided by the United States Geological Survey's Earthquake Hazard Program.