Sebastian+B.+and+Willy+W.+-+Earthquakes

== =Earthquakes= The sudden release of stored energy in the Earth’s crust creates seismic waves which produce earthquakes. At the Earth's surface, earthquakes may manifest themselves by a shaking or displacement of the ground, which may lead to loss of life and destruction of property. The friction created by grinding tectonic plates causes earthquakes. The strain on the plates becomes so great that the ground begins to shake. = = = = = = Earthquakes may occur naturally or as a result of human activities. Smaller earthquakes can also be caused by volcanic activity, landslides, mine blasts, and nuclear tests.

How Earthquakes are measured
Earhquakes are measured on a Richter Scale. The Richter Scale was developed in 1935 by Charles Richter and Beno Gutenburg. This scale, or more specifically, the local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It is a base-10 logarithmic scale obtained by calculating the logarithm of the combined horizontal amplitude of the largest displacement from zero on a seismometer output. The Richter Scale, explained:


 * ~ Description ||~ Richter Magnitudes ||~ Earthquake Effects ||~ Frequency of Occurrence ||
 * Micro || Less than 2.0 || Microearthquakes, not felt. || About 8,000 per day ||
 * Very minor || 2.0-2.9 || Generally not felt, but recorded. || About 1,000 per day ||
 * Minor || 3.0-3.9 || Often felt, but rarely causes damage. || 49,000 per year (est.) ||
 * Light || 4.0-4.9 || Noticeable shaking of indoor items, rattling noises. Significant damage unlikely. || 6,200 per year (est.) ||
 * Moderate || 5.0-5.9 || Can cause major damage to poorly constructed buildings over small regions. At most slight damage to well-designed buildings. || 800 per year ||
 * Strong || 6.0-6.9 || Can be destructive in areas up to about 100 miles across in populated areas. || 120 per year ||
 * Major || 7.0-7.9 || Can cause serious damage over larger areas. || 18 per year ||
 * Great || 8.0-8.9 || Can cause serious damage in areas several hundred miles across. || 1 per year ||
 * Rarely, great || 9.0-9.9 || Devastating in areas several thousand miles across. || 1 per 20 years ||
 * Meteoric || 10.0+ || Never recorded; see below for equivalent seismic energy yield. || Unknown ||

Earthquakes always occur at the borders of tectonic plates. The effects of the the earthquakes dramatically affect the shape of crust. The most devastating Earthquake was a measured 8 on the Richter scale in Shensi, China on January 23, 1556. Although not the highest ever magnitude, it had the greatest number of casualties, with 830,000. The largest earthquake ever recorded occured in Chile on May 22, 1960, it recorded a whopping 9.5 on the Richter Scale.

Where do they occur?
Earthquakes always occur on the boarder lines of the continental plates of the world. Coincidentally, earthquakes occur all along the mountain ranges of the world. An example of this is along the coast of California where the Cascade mountains appear. Athough eartquakes do not always occur in the mountain ranges, a fair majority of them do. California is known for having so many earthquakes every year. California has so many earthquakes because of its location on the map. As you can see on the map above, California is located right on the boarder of to continental plates as is heavily concentrated with earthquakes over the course of time.

[[image:http://upload.wikimedia.org/wikipedia/en/0/0e/Fault_types.png width="144" height="360" align="left" link="http://upload.wikimedia.org/wikipedia/en/0/0e/Fault_types.png"]]Why do they occur?
Earthquakes occur because of the movement of the continental tectonic plates. The shifting of the plates causes the ground above to move rather slowly. The crashing together of the tectonic plates causes the ground above to shake severely or not so severely, depending on how intence the crashing of the plates is. If the crash is hard and intence, then it may result in a good sized earthquake. However, if it is just one of the 8,000 tiny bumps that occur underneath the surface of the earth because of the tectonic plates. These little bumps are called microearthquakes and occur everyday. They have an average magnitude of about 2.0 on the Richter scale and they are so harmless, that they have no effect on the the surface that lies above them.

Conclusions
1. Earthquakes come in different intensities, and they can be harmless or harmful. 2. They are caused by the moving of the tectonic plates. 3. Earthquakes intensity can be measured on the Richter scale. 4. Earthquakes occur along the boarders of the continental plates. 5. Earthquakes are caused from stored energy from under ground