Earthquake Anatomy

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	Just below the epicenter is the place where the earth actually moves. That place is called the hypocenter of an earthquake. That is really where the earthquake starts.
Faults are almost vertical weak spots or fractures in the bedrock found in the Earth's crust. These weak spots can rub against each other three different ways. Strike-slip faults move mostly from side to side, but they can move from side to side. Dip slip faults are leaning faults. If the dip-slip fault makes one of the pieces of land move upward, it is called a normal fault. If part of the land moves up then it is called a thrust fault.
	An earthquake starts below the earth at the focus point. The focus point is where the earth fractures. When it reaches the surface of the earth that spot is called the epicenter.
After an earthquake has finished shaking the earth and things are quiet for awhile, new smaller shakes happen. These are not usually as strong as the earthquake itself, but aftershocks do make the earth shake. The stronger the earthquake is determines how long aftershocks will occur and how strong the aftershocks will be. Stronger earthquakes make stronger aftershocks that can happen even years after the main earthquake.
	Buildings on top of the Earth's crust tremble and we can see and feel that. Seismic waves called body waves also move through the inside of the earth. They move away from the epicenter in all directions at the same speed a lot like the waves in a puddle move when a rock is dropped into it. These waves are called P waves.

When you ride in a car you use the accelerator to go faster and the brake to go slower or stop. You can make the car accelerate(go faster) and decelerate(slow down). When you change speeds, or velocity, it is called acceleration. When an earthquake makes the ground shake it experiences acceleration.

P & S waves

long & regular waves

Earthquake Photos Citations
Click each image to see its citation.