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Earthquake event in Assam

Earthquake event in Assam

  • Recently, several northeastern states, including the state of Assam, have witnessed an earthquake of magnitude 4 Richter scale.
  • Earthquake tremors have been felt from Arunachal Pradesh to the northern part of West Bengal and Bihar.
  • The ‘Kopili Fault Zone’ which is located close to the Himalayan frontal thrust ‘is believed to be the cause of this earthquake. This fact has been informed by the National Center for Seismology (NCS).
  • It may be noted that the National Center for Seismology is a nodal agency under the Ministry of Earth Sciences, Government of India to monitor seismic activities.

Key points:

  • The Himalayan frontal thrust, also known as the main frontal thrust, is a geological fault zone bordering the Indian and Eurasian tectonic plates.
  • The ‘Kopili Fault Zone’ is a 300 km long and 50 km breadth spread in the northeastern region of India to the western part of Manipur, Bhutan, Arunachal Pradesh and Assam.

What is earthquake?

  • Earthquake is a natural phenomenon. In simple words, a sudden vibration on the surface of the Earth is called an earthquake. The reason for this sudden vibration is the energy emanating from inside the Earth, which spreads in all directions and vibrates the Earth.
  • An earthquake is a type of wave energy that moves on the surface of the Earth and is measured by seismographs. Excessive movement of these waves can cause a disastrous situation on Earth.

Focus: The place below the surface of the Earth from which seismic waves originate is called Focus or Hypocenter.

Epicenter: The place where earthquake waves first reach the surface of the Earth is called Epicenter. An earthquake center is usually a location located perpendicular to the origin or focus.

Seismic waves: Seismic waves are divided into three categories

Primary Waves- ‘P’:They move like sound waves. They have high speed and can move in all three mediums, solids, liquids and gases. Most motion occurs in solid medium.

Secondary Waves- ‘S’: Their speed is less than the primary waves. These waves are generated after P waves and they do not move in the liquid medium.

Surface or Long Waves- ‘L’: These waves are the most deadly seismic waves that move only on the surface. This destruction is caused by this wave.

Causes of earthquake

The Geological actions that are mainly caused by plate tectonics are considered to be the cause of most of Earth’s earthquakes. Apart from this, other major reasons are as follows-

  • Volcanic action
  • Folding and Faulting
  • Dispersion of geological gases
  • Human factor

Seismic zone in India

On the basis of seismic history, the country has been classified into four seismic zones by the Bureau of Indian Standards- BIS.

Zone-V: Seismically, this zone is the most sensitive zone, where the most intense tremors have been seen. This region includes Northeast India, parts of Jammu and Kashmir, Ladakh, Himachal Pradesh, Uttarakhand and parts of Kutch in Gujarat. , North Bihar and includes parts of the Andaman and Nicobar Islands.

Zone-IV: This zone includes Jammu and Kashmir, Ladakh, Himachal Pradesh, Delhi, Sikkim, Uttar Pradesh, Bihar and northern parts of West Bengal, parts of Gujarat and Rajasthan, and small parts of Maharashtra near the west coast.

Zone-III: Kerala, Goa, Lakshadweep Group, Uttar Pradesh, Gujarat and the remaining parts of West Bengal, parts of Punjab, Rajasthan, Bihar, Maharashtra, Madhya Pradesh, parts of Jharkhand, Chhattisgarh, Odisha, Andhra Pradesh, Tamil Nadu and Karnataka is included.

Zone-II: Includes the remaining parts of the country. It is to be noted that the Bureau of Indian Standards has divided the country into four seismic zones by joining two zones (first and second) together.

Source: PIB

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