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Earthquakes
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Wikipedia-Earthquakes
Watch this video for earthquakes
About Earthquakes

Devastating earthquakes happen everyday. As we all know and Haiti and Chile have had heavy earthquakes in the past few months. Earthquakes are measured by their own magnitude. The magnitude is measured by the Richter Scale.The Richter Scale was invented by Charles F. Richter in 1934. There are different types of scales used to measured earthquakes like the Mercalli. Earthquakes have a couple different parts to it. The focus is the point beneath Earth's surface were rock that is under stress, then breaks to create an earthquake. The epicenter is the point directly above the focus. The epicenter is the first pace that feels the first seismic waves.

Seismic Waves
There are two different types of seismic waves. There are P waves and S waves. P waves stand for primary waves. S waves stand for secondary waves. If you could guess, P waves would come first and s waves would come second. P waves can move through solids and liquids. Unlike P waves, S waves can only travel through liquids. Also S waves travel from side to side and P waves travel straight.

Once the P waves and S waves have reached the surface, they turn to surface waves. Even though surface are much slower than P waves and S waves, surface cause more damage to the Earth's crest. Earthquake_bldgs.jpg

Locating Epicenters
To locate the epicenter of an earthquake, scientist must know three point from which people of the city felt the vibrations of the earthquake. If a scientist had less than three, they wouldn't be able to locate the epicenter. When all the circles line up, the scientist have successfully found the epicenter
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Hazards of Earthquakes
There are many hazards from many earthquakes. Liquefaction is the biggest factor from earthquakes. Liquefaction occurs when an earthquake's violent shaking turns loose, soft soil into liquid mud. After the earthquake the aftershock comes. An aftershock is an earthquake that occurs after a large earthquake in some area. Aftershocks may even occur months after the main earthquake has occur. To take the best precaution during an earthquake, drop, cover, and hold.

When comes to measuring earthquakes and how they move, scientist have four different measuring machines. They are: creep meter, laser-ranging devices, tilt meters, and satellite monitors.

Where You Live
If you life next to the east coast of the United States, you are probably going to be safe from major earthquakes. On the other hand, if you life next to the west coast of the United States, you are a high risk of major earthquakes. Geologist can determine earthquake risk by location where faults are active and where past earthquakes have occurred. The states California, Washingtoneqfig6.gif, and Alaska have the highest risk of major earthquakes than any other state in the United States. The risk are high because this is where the Pacific plate and the North American plate meet.

How Earthquakes Form
Shearing, tension, and compression work over a million years to change the shape and volume of rock. Tension is the force that pulls the rock, or surface, apart. Shearing cause the rock to slide in different direction. Compression is force that pushes the rocks together to make a hill or eventually a mountain.

Faults
There are three different types of faults. Strike-slip faults, normal faults, and reverse faults are the three different types of faults. Strike-slip faults are faults that have rocks on each side of the fault pass each other with little up or down movement. A normal fault is a fault that is at an angle. This way, one rock is on top and the other on the bottom. A reversed fault is a fault that is the complete opposite as a normal fault.


Earthquakes in General
Many earthquakes happen everyday. Ten hours ago an earthquake occur in Baja California, Mexico. Two hours before, a 3.7 earthquake occurred at the same location. Then two days ago another earthquake occurred in Southern California. That is is also in the same region of a map. these earthquakes are only the few that occur everyday. These earthquakes are only some of the smallest earthquakes. The biggest earthquake so far, in the United States, was locates in Prince William Sound, Alaska. this has been the largest earthquake in the United States recorded.

Earthquakes all over the world lead to disaster and total destruction of towns and and even large cities. Earthquakes can leave many people homeless for months or even years. Also, earthquakes can mix harmful chemicals in to the air. With a big city, many people breathe those harmful chemicals. That leads to disease that could be spread around next door neighbor cities or even to a different states, if it was a large earthquake. Many people die each year from earthquakes happening all over the world. From building collapsing to disease spreading, earthquakes are harmful, natural occurrences. the worst part of the fact is, scientist can not tell whether an earthquake is going to happen in a day, week, or month.



Sources
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Pasachoff, Jay M., and Thomas R. Wellnitz. "Earthquakes." Prentice Hall Science Explorer. By Joseph D. Exline. Upper Saddle River: Prentice Hall, 2002. 142-72.
http://en.wikipedia.org/wiki/Earthquake
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