An earthquake is a wave-like movement of the earth's surface. The earth's crust and upper part of the mantle push and move against one another along fault lines. When rock masses slip along a fault, the energy of an earthquake is released in seismic waves.

While earthquakes are sometimes believed to be a West Coast phenomenon, there are 45 States and territories throughout the United States that are at moderate to high risk for earthquakes, including the New Madrid fault line in the Central States. Because it is impossible to predict when an earthquake will occur, it is important that you prepare ahead of time.

Earthquake monitoring is conducted by the U.S. Geological Survey, the National Oceanic and Atmospheric Administration (NOAA), and universities throughout the United States.

Click on this link to learn about the measurement of earthquake intensity.