Interesting Earthquake Facts

Earthquakes are one of the deadliest natural disasters and are responsible for widespread damage. The intensity of earthquakes can be measured after their occurrence but scientists have still not been able to find a way to predict earthquakes before they occur. The information that follows provides some interesting facts on earthquakes.
| Thursday, December 11, 2008
The mere mention of the word earthquake conjures up images of buildings crumbling to pieces like a pack of cards. Not many people know that every year as many as half a million earthquakes occur worldwide. However only around 20 percent of these earthquakes are actually felt and only a few hundred of these cause any real damage. So what causes earthquakes and how are earthquakes detected" Earth interiors are composed of layers like that in an egg. The shell of the earth is the crust and this is made up of major tectonic plates. The next layer is the mantle and this is made up of solid rock. Even though this layer is of solid rock heat dissipating from the core causes the rock to slowly flow in convention current and this causes the plates to move up to several centimeters every year. When these plates collide or grind against each other stress is created and with the resultant energy the plates attempt to return to the original position. This results in earthquakes. The magnitude of the earthquake is actually the measurement of the earthquake’s energy. This magnitude does not vary as per the location. The intensity of  an earthquake is determined based on the extent of shaking generated by the earthquake and this intensity can change as per the location.  

Here are some informative and interesting facts about earthquakes:
  1. The earliest reported earthquake was in 1769 and was reported by the Spanish explorers. The location of this earthquake was around the southeast region of Los Angeles.

  2. The primitive seismographs were built in 1751. At that time no one could determine the reason behind the earthquakes. The faults or fault lines were discovered in 1855 and that was when faults were deemed responsible for the earthquakes.

  3. Earthquakes are responsible for tsunamis. An underwater earthquake results in displacement of ocean water at a very fast pace and this is what causes tsunamis.

  4. The hypocenter in an earthquake is the point where the rupture of the fault originates while the epicenter is located on the surface and over the hypocenter.

  5. In the San Francisco earthquake of 1906 it is believed that more damage was caused because of the fire after the earthquake than the earthquake itself.

  6. California has around 10,000 earthquakes on an average every year. However many of these earthquakes are of minimum intensity and often go unnoticed. A few hundred of these earthquakes are noticed and recorded. A large earthquake is often followed by aftershocks for months after the earthquake.

  7. The movement of water within a body of water caused as a result of the ground shaking in an earthquake is called a Seiche ("Saysh"). Such a movement is often seen in swimming pools following an earthquake. Such a movement can continue for minutes and even up to a few hours after the earthquake.

  8. There is no correlation between weather and earthquakes even though some people believe that earthquakes may be related to extreme cold weather or even muggy weather.

  9. Usually the depth of any earthquake is around 50 miles under the earth’s surface.

  10. Aristotle discovered in 350 B.C that soft ground shakes far more in an earthquake than hard rock.

  11. California’s complex landscape has been attributed as the reason for the network of fault lines running underneath this area. Faults often occur when sudden changes take place in the structure of the rocks. These faults include strike slip faults or dip slip faults. In strike slip faults the rocks tend to move past other rocks in a horizontal manner. Dip slip faults are where the movement is parallel to each other.

  12. The highest magnitude earthquake ever to be recorded occurred on May 22, 1960 in Southern Chile. This earthquake measured 9.5 and more than 2000 people were killed in this earthquake. Also 2 million people became homeless following this earthquake.  This same earthquake was also responsible for causing a tsunami as far away as Japan and this killed around 138 people.

  13. The largest earthquake ever to be recorded in United States occurred in Alaska on March 28, 1964 and the magnitude of this earthquake was 9.2.

  14. Earthquakes of the magnitude 8 and higher are considered as major earthquakes. On an average around 1 million earthquakes of small magnitude are experienced every year.

  15. United States, North Dakota and Florida experience fewest earthquakes while California and Alaska experiences the most earthquakes. Alaska in fact is seismically one of the most active regions on the earth.

  16. The deadliest of all earthquakes occurred on January 23, 1556 in China and as many as 830,000 people died in this earthquake.

  17. Animals seem to be able to detect earthquakes much before they occur but they cannot be used to predict the earthquakes. This is because their behavior is not consistent and scientists cannot determine exactly what causes them to predict the earthquakes.

  18. Sometimes lights are also seen in the sky in the area surrounding the seismic instability. This can be seen up to three weeks before the earthquake. Theories indicate that the lights are a result of ionized gases that are released from the earth. However this is not noticed every time and so cannot be used as a predictor.
   
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