Earthquakes

An earthquake is the shaking of Earth's surface caused by movement of rock in the crust.

Focus of an earthquake

The focus is also called the hypocenter of an earthquake. The vibrating waves travel away from the focus of the earthquake in all directions. The waves can be so powerful they will reach all parts of the Earth and cause it to vibrate like a turning fork.

Epicenter of an earthquake

Directly above the focus on the Earth's surface is the earthquake epicenter. Earthquake waves start at he focus and travel outward in all directions. Earthquake waves do not originate at the epicenter.
Most news stories on earthquakes will list the epicenter of an earthquake and then tell how deep the earthquake was from the epicenter.

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Most eartquakes occur along faults. A fault is a brak in the crust, where rock moves. If the movement is sudden, it can send out waves of energy that move through the crust.

Movement between two plates can cause earthquakes.