How Does an Earthquake Occur?


An earthquake is the shaking of the surface of Earth due to the sudden release of energy in the Earth’s crust, as a result, seismic waves (also known as S waves)are created. The seismic activities in an area determine the type and intensity of the earthquake.

What Causes an Earthquake?

  • Earthquakes are caused due to sudden tectonic movements in the earth’s crust.
  • When the tectonic plates slide over one another, there is a cause of orogeny which results in earthquakes and volcanoes.
  • These disturbances cause vibrations that spread in all directions. As there is a relative motion of these plates, there is stress built up, which breaks by releasing the stored energy known as shock waves.
  • This causes a release of energy, and the energy waves travel in all directions. The point where the energy is released is called the focus of an earthquake or hypocentre.
  • The point on the surface of the earth which is vertically above the focus is called the epicentre. It is the first place to experience the waves.

Earthquake zones in India

There are a total of 5 earthquake zones in India, and they are:

  • Zone 5: Highly prone to earthquakes. Punjab, Kashmir, and North-East India.
  • Zone 4: Parts of Delhi, Jammu, Bihar, and Indo-Gangetic basin.
  • Zone 3: Moderate damage risk. Western Himalayan plains, Andaman and Nicobar Islands.
  • Zone 2 and 1: Low damage risk.

Effect of earthquake

  • Surface waves that are near the epicentre are responsible for the earthquake. The intensity of ground shaking depends on the duration, local geology, and distance.
  • Damage to a man-made structure.
  • An outbreak of fire and spilling of hazardous chemicals.

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