This document provides information about earthquakes including:
1) Earthquakes are caused by a sudden slip on a fault when stress overcomes friction, releasing energy as seismic waves.
2) The magnitude of an earthquake is measured on the Richter scale based on the amplitude of seismic waves.
3) The 2011 Tohoku earthquake in eastern Japan was magnitude 9.0 and caused tsunamis, damage to buildings/infrastructure, economic impacts, and loss of life.