An earthquake is the result of a sudden release of energy in the earth's crust that causes the ground to shake, lift up, or separate, creating uneven surfaces, gaps, or holes. The strength of earthquakes is expressed by magniture on the Richter scale. An earthquake of magnitude 7 can cause serious damage over large areas. Earthquakes under magnitude 3 are rarely noticed by humans.
Some serious hazards of earthquake activity are tsunamis, landslides, damaged buildings, broken glass from windows, falling objects, plus serious injury and fires if electrical wires fall and gas pipes break.
Download earthquake checklist from National Fire Protection Agency (NFPA).