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What is an earthquake?

Published On: Jul 22 2011 02:49:13 PM CDT

An earthquake, also known as a quake, tremor, temblor or seismic activity, is the result of a sudden release of energy in the Earth's crust that creates seismic waves.

Earthquakes are measured with a seismometer; a device which also records is known as a seismograph.

At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacing the ground.

When a large earthquake epicenter is located offshore, the seabed sometimes suffers sufficient displacement to cause a tsunami.

The shaking in earthquakes can also trigger landslides and occasionally volcanic activity.

In its most generic sense, the word earthquake is used to describe any seismic event, whether a natural phenomenon or an event caused by humans, that generates seismic waves.

Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.

An earthquake's point of initial rupture is called its focus or hypocenter.

The term epicenter refers to the point at ground level directly above the hypocenter.

More than a million earthquakes rattle the world each year.

The West Coast is most at risk of having an earthquake, but earthquakes can happen in the Midwest and along the East Coast as well.

Earthquakes can be felt over large areas although they usually last less than one minute.

Earthquakes cannot be predicted, although scientists are working on it!