Earthquake and related terms

Earthquake is a term which is used to denote the relative movement of the earth surface under the influence of release of the strain energy stored in faults.  The faults are the planes along which the two earth surface can move under the influence of the forces created by the movement of the earth crust material. The faults are classified generally in three categories known as normal, reverse or strike-slip faults. 

Seismic Focus: This is the point where the earthquake starts or this is the place where the release of the energy takes place. It can be at several 100 kilometers below the earth surface. This focus can be considered as shallow or deep if the depth is less than 70 Km or more than 300km respectively. The focus of depth in-between the two are considered to be medium depth.

Epi-centre: This is the place on the surface of the earth exactly over the seismic focus of the earthquake. This is the place where the intensity of the earthquake will be maximum because it is nearest to the focus of the earthquake.

Magnitude

Earth crust generally consist of lava and it is not at rest. The movement of the crust material results in different forces which cause the volcanic eruption or the earthquakes.  Earthquakes are observed using seismometers. using them we can prepare the seismographs. Magnitude of earthquake is measured on a scale known as Richter scale. It is a logarithmic scale with log of the value to the base 10. It was developed by Sir Charles Francis Richter in 1935 with his colleague Mr. Beno Gutenberg.

So a earthquake of magnitude 7.0 is 10 times more powerful than the earthquake of magnitude 6.0.  The Richter scale is graduated from 1 to 9, means 1 being the lowest magnitude but there is no higher limit to the earthquake so 9.0 is not the highest. It is an open ended scale whose higher end is open. 

Although another scale known as moment magnitude scale has been introduced but the Richter scale is still used in many countries. 

Earthquake of scale 3 to 5 are considered normal but the earthquake with a magnitude of 7 or higher are considered disastrous.

Now look at the following data with special focus on the magnitude and the numbers of the lives taken, and you will know that we can apply some mitigation measures to this natural phenomenon:- 

Some major earthquakes in the history of India

• October 8 2005 - Kashmir, Himachal Pradesh and Pakistan claimed more than 80,000 lives. The recorded magnitude was 7.6
• December 26, 2004 -  Off west coast of Sumatra - According to wiki-records Claimed 2,83,106 lives. The magnitude was 9.0 to 9.3. It was the third most deadliest earthquake that ever occurred.
• January 26, 2001 -  Kutchh - Also known as Gujarat earthquake. Claimed live more than 20,000. The magnitude was 7.6.
• August 15, 1950  - Tibetan Plateu -Arunachal Pradesh -China Border - Claimed 1,526 live (wiki records). The magnitude was 8.5.
• It is the deadliest earthquake recorded in the mainland because the 2004 earthquake started below the water. 

Now you can see in the facts that the lives taken is proportional to a number of factors such as the magnitude of the earthquake, the intensity of the population living in the area etc. Those are facts which are directly reflected from the data above. In the early days the population intensity was not much so the number of deaths is less in the early earthquakes. 

Many Seismologist say that it is not the earthquake do not take lives but it is the improper design of the houses which kills people. I think that houses can be constructed earthquake resistant but never the earthquake proof. So if you are going to construct a house try to consult a Civil Engineer to help your self. 

Save yourself from the earthquake

If earthquake occurs then the things that one must do instantly are listed below:

1. The first thing that you should do if you can is to run to an open space like a pay-ground. 
2. If you can not do the (1) then you should either hide under some hard table or bed or otherwise shift yourself to the places like corners of a room. 
3. Turn off the main switch of the house if possible because it can save you from the fire hazards. 
4. Most important thing is to keep your self cool and calm and then act, don't run here and there under stress. 

I never experienced a disastrous earthquake and I hope I never will and I wish the same for you. Have a safe future.

Please feel free to write in some comments good or bad both welcome.