Answer Writing Practice for UPSC IAS Mains Exam: Paper - II (General Studies – I) - 07 August 2018

Answer Writing Practice for UPSC IAS Mains Exam

UPSC Syllabus:

  • Paper-II: General Studies - I (Indian Heritage and Culture, History and Geography of the World and Society)

Q. Recently Indonesian tourist island of Lombok witnessed a deadly earthquake. Discuss about the causes of earthquakes and their distribution across the world. Suggest remedial measures to mitigate the disaster risk of earthquakes. (250 words)

Model Answer:


  • Why in news?
  • What is an Earthquake?
  • Causes of Earthquakes
  • Distribution across the world
  • Remedial measures to mitigate risk
  • Conclusion

Why in news?

An earthquake measuring 6.9 on the Richter Scale struck Lombok island of Indonesia on Sunday, according to the United States Geological Survey, killing over 90 people and injuring 200 others.

What is an Earthquake?

Earthquake is a vicious tremor, rolling or hasty shock on surface of earth's crust, sending out a sequence of shock waves in all directions from its place of source which is known as epicenter.

Earthquake is considered as the most dangerous natural disaster causing massive destruction and causality to human life and debilitating impact on societies. According to a moderate estimate about 30,000 earthquakes occur every year.

An earthquake's power is measured on the Richter scale using an instrument called a 'seismometer'. The Richter scale is numbered 0-10.

Causes of Earthquakes

Earthquakes are caused by disturbances in the interior of the earth and there disturbances can be caused by factors such as –

  • Tectonic Movements:The disturbances inside the earth are called tectonic movements. These forces bring about changes on the earth surface and physical features like mountains, plateaus and rift valleys are formed. Most disastrous earthquakes are caused by tectonic forces. Tectonic forces create tension and pressure and the stress begins to build up inside the earth. When the stress tends to be more than what the rocks of the earth can bear, the rocks are broken and displaced from their state of equilibrium. It is known as faulting. The energy accumulated during faulting is released. This release of energy gives rise to mighty waves. These waves originate from a point called Focus in the interior of the earth and then spread out in all directions. On the surface whatever comes into their contact begins to vibrate.
  • Volcanic Eruptions:The volcanic eruptions are often very violent and cause vibrations in the earth crust. Sometimes the vent of a volcano is blocked temporarily and explosive eruption takes place suddenly causing tremors in the earth crust.
  • Other Reasons:The roofs of underground caves sometimes give way and release great force to cause minor tremors in the earth crust. Nuclear explosions also release massive energy to cause tremors in the earth crust.

Distribution across the world

It is true that the earthquakes can happen in any part of the world. But in the areas of faulting and folding or of crustal weakness, the frequency of earthquakes is more than anywhere else. The earthquakes are concentrated in two main belts –

  • Circum-Pacific Earthquake Belt:This belt includes all the coastal areas around the vast Pacific Ocean. This belt extends as an isostatically sensitive zone through the coasts of Alaska, Aleutian Islands, Japan, Philippines, New Zealand, North and South America. This zone accounts for 68% of all earthquakes on the surface of the earth. The most talked about earthquake areas in this zone include Japan, Chile, California and Mexico.
  • Mediterranean-Asia Earthquake Belt:This belt begins from Alps mountain range and passes through Turkey, Caucasus Range, Iran, Iraq, Himalayan Mountains and Tibet to China. One of its branches passes through Mongolia and Lake Baikal and another branch extends to Myanmar. About 31% of world's earthquakes are located in this region.
  • Other Areas:These include Northern Africa and Rift Valley areas of the Red Sea and the Dead Sea. In addition to these, the ocean ridges are also active earthquake zones.

Remedial measures to mitigate risk

  • In order to lessen the impact or to avoid the risks from earthquakes, it is necessary to predict their occurrence through early warning systems. Another way to lessen the impact of disaster is seismic risk assessment, which enables planners to recognize areas at risk of earthquakes and their effects. This information is used to tackle the third area of earthquake risk reduction-mitigation measures.
  • Buildingsin the earthquake prone areas should be made earthquake resistant with strength, stiffness and inelastic deformation capacity.
  • Policy decisionsabout construction of structures with due approval from specified authorities have to be taken.
  • Encourage government and financial institutions to establish policies directed towards understanding and preparing for future earthquakes. Incorporate experience and research findings into recommended practices and
  • Supporting research and development in the field of disaster management. Advance engineering knowledge through problem focused research
  • Encouraging improvements in emergency response coordination and
  • Involving community in the process through education and awareness for pre and post disaster activities and evolving educational environment and technical training for the technical students and community.
  • Linking and preparing Local NGO’s in a network for emergency services. These are few important long-term, medium-term measures to mitigate the loss of earthquake.


Not all natural disasters can be prevented. However, the impacts can be lessened with proper planning and notification systems. 

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