Q:

Why does California have so many earthquakes?

A:

A large number of earthquakes occur in California because it is home to hundreds of known faults. At least 200 of the faults in California are considered potentially hazardous, and more than 70 percent of the population of the state lives within 30 miles of a fault.

A fault is a fracture in the Earth's crust where one side has moved in relation to the other. A fault can be very short, or it can be hundreds of miles in length. The plates of the Earth are in constant, but very slow, motion. California lies on the Pacific plate, which is part of the North American plate; the boundary between these two plates is the San Andreas Fault, which is a fracture that runs from Imperial County to Humboldt County.

When two sides of a fault such as the San Andreas fault slip suddenly against one another, an earthquake results. The Pacific and North American plates move about 1.5 inches past one another annually, and the friction caused by this passage causes stress that is released by slippage along the fault plane. This results in the shaking feeling of the earthquake.

Although California is known for its many earthquakes, Alaska has more earthquakes per year.

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    A:

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