Earth quakes are a disastrous phenomenon. Earthquakes are usually associated with losses in lives and money. Scientists can't predict until now the occurrence of earthquakes before they happen.
How earthquakes happen?
Earth's crust consists of plates called tectonic plates, under these plates there is something called magma. Magma is molten rocks under the earth's crust .These magma layers are in a continuous motion and evolving heat. The heat evolving from this magma keeps the tectonic plates in continuous motion and rubbing against each others. This rubbing of plates accumulates pressure on the plates' sides. As the pressure between the plates increases, the rocks between the plates start to break causing disturbance between plates. This disturbance causes sudden movements of the plates upwards or downwards. Above these plates there are continents, so any movements in these plates causes movements in the continents.
During this motion plates rise up and down some plates totally sink in magma and magma dries up and forms a new plate while other plates rise up and form hills or mountains.
Causes of earthquakes
There are two main reasons that cause earth quakes. The first reason is the movements of tectonic plates and this is the most devastating kind, the second reason of earthquakes is the vibrations that precede the volcanic eruptions these small earthquakes just help us predict the occurrence of volcanic eruptions. There is also another reason for earthquakes, it's the earthquakes caused due to human activities such as pumping fuels at deep points under earth and using explosives.
Measurement of earthquakes
Earthquakes are measured by a scale called Richter scale, it's the most common scale used to measure the intensity released from the earthquakes. This scale is named after Charles Francis Richter a scientist from U.S.A. This scale measures the intensity of earthquakes which is shown on a device called seismograph which shows the direction and force of the earthquake.
There are about 4,000 stations around the world that measure intensities of earthquakes.
And according to the U.S.G.S. (U.S geological survey), here are some statistics about earthquakes:
- There are about 9,000 small earthquakes that occur daily all around the world and most of them are measured to be 3 Richter.
- There are about 49,000 earthquakes a year that their intensities range from 3 to 4 on Richter scale.
- There are about 6,000 earthquakes a year that their intensities range from 4 to 4.9 on Richter scale.
- There are about 8,000 earthquakes a year that their intensities range from 5 to 6 on Richter scale.
- There are about 120 earthquakes a year that their intensities range from 6 to 7 on Richter scale.
- There are about 18 earthquakes a year that their intensities range from 7 to 8 on Richter scale.
- There is nearly one earthquake a year that its intensity exceeds 8 on Richter scale.
Deadly earthquakes over time
The strongest earth quake ever recorded took place at Chile in 1960; it was measured to be 9.6 on Richter scale which is so destructive. This earthquake resulted in the death of 6,000 people just in Chile. There was also a tsunami that followed that earthquake, that tsunami hit Japan and Hawaii and killed more people.
The strongest earthquake ever recorded to hit U.S.A. was in 1964 at the coast of Alaska it was measured to be 9.2 on Richter scale. This deadly earthquake was in action for continuous 7 minutes without stopping despite that 9.2 on Richter scale indicates that is a very destructive earthquake. Some regions of land moved about 56 feet due to that earthquake. Even though the earthquake was so deadly but the number of people that died was little compared to othe earthquakes that are that strong, there was 150 people killed that is because the location where the earthquake took place had a small population.
The largest number ever recorded of dead people from an earthquake was at china in 1556, 830,000 people died from that earthquake.
Can we depend on animals to predict an earthquake?
Many stories talk about the strange behavior of animals before the occurrence of an earthquake. As in china in 1975 people started noticing strange behaviors of animals. Dogs, cats, and birds were restless, the dogs were howling all the time. The government at china decided to evacuate the city from all people and after two days a strong earthquake occurred there.
Some historians also mentioned the fact of some animals like snakes, rats, and birds leaving the city of Helice in Greece two days before the occurrence of a great earthquake.
But most scientists don't believe that animals feel the occurrence of earthquakes before they happen because there is no strong evidence that proves that fact. Scientists found out that dogs have a stronger ability to feel the underground vibrations than man does, but this is not enough for scientists to be sure that animals like dogs can feel the occurrence of earthquakes before they happen.
Seismologists can't predict until now the occurrence of an earthquake.
Results of earthquakes
Earthquakes cause a lot of damage to structures and results in great losses in lives. They also cause tidal waves, tsunamis, ground rupture, fires, and liquefaction of soil. Liquefaction of soil is when the soil loses its strength it becomes like soft sand which can swallow up a complete building.
Countries of high earthquakes activity
Alaska, U.S.A., Japan, China, and Russia are the countries that have the greatest earthquakes activity
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