An earthquake is any movement of the ground, that is based on the surface. The cause of the shaking must origionate at one point. This shaking can be very destructive, and can break buildings, cause fires, take down power lines, break water mains, crack ground and much more.

	Earthquakes mainly occur along where volcanoes are, the plates. However, earthquakes also happen on faults. There is a major fault running through California, the San Andreas Fault. Because of this, there are many earthquakes in San Francisco
Earthquakes are very destructive and have been integrated into every aspect of society, from buildings to myths. Now, in places like San Francisco almost all buildings are built to withstand earthquakes. These buildings are made so that during an earthquake, they will only crack, not crumble and fall down. These are much safer for people to go in.

More information about how/why earthquakes occur can be found [here]

Information about major past earthquakes can be found [here]

Earthquake links can be found [here]

More earthquake pictures can be found [here]

Information on how earthquakes are classified can be found [here]