An earthquake is the sudden, sometimes violent movement of the earth's surface from the release of energy in the earth's crust. Earthquakes are one of the most costly natural hazards faced by the Nation, posing a risk to 79 million Americans in 39 states. Although there are no guarantees of safety during an earthquake, identifying potential hazards ahead of time and advance planning can save lives and significantly reduce injuries and property damage. The number one cause of death in an earthquake is running out of a building and being struck by falling debris! With the stringent construction standards in force in the U.S. today, you are far safer staying inside a building when an earthquake occurs.