Context

An earthquake of magnitude 4.1 on the Richter scale struck Mizoram, the fourth in the northeastern state in as many days.

About

• An earthquakeis an intense shaking of Earth’s surface. The shaking is caused by movements in Earth’s outermost layer.
• The Earth is made of four basic layers:
  • a solid crust
  • a hot, nearly solid mantle
  • a liquid outer core
  • a solid inner core
• The solid crust and top, stiff layer of the mantle make up a region called the lithosphere, which is actually made up of giant puzzle pieces called tectonic plates.
• Tectonic plates are constantly shifting as they drift around on the viscous, or slowly flowing, mantle layer below.
• This non-stop movement causes stress on Earth’s crust. When the stresses get too large, it leads to cracks called faults.
• When tectonic plates move, it also causes movements at the faults. An earthquakeis the sudden movement of Earth’s crust at a fault line.
• The location where an earthquake begins is called the epicenter.
• An earthquake’s most intense shaking is often felt near the epicenter. However, the vibrations from an earthquake can still be felt and detected hundreds, or even thousands of miles away from the epicenter.
• The energy from an earthquake travels through Earth in vibrations called seismic waves. Scientists can measure these seismic waves on instruments called

Why India’s north-east is prone to earthquake?

• Geomorphologic ally, North East India is located in an earthquake prone zone (zone v) of the Indian subcontinent.
• In this region earthquake comes with land sliding flood and along with series of smaller magnitude earthquakes.
• Seismologists consider India's mountainous northeast region as the sixth major earthquake-prone belt in the world.
• The northeast has seen some of the biggest quakes in history.
  • In 1897, a Shillong-epicentred quake measured 8.2 on the Richter scale, while in 1950, an earthquake in Assam measuring 8.7 on the Richter Scale forced the Brahmaputra river to change its course.

Seismic zones in India

Seismic zones in the Indian subcontinent are divided into the following four seismic zones (II, III, IV, and V):

• Seismic Zone II: Area with minor damage earthquakes corresponding to intensities V to VI of MM scale (MM – Modified Mercalli Intensity scale). It covers the areas which are not covered by other three seismic zones discussed below.
• Seismic Zone III: Moderate damage corresponding to intensity VII of MM scale. It comprises Kerala, Goa, Lakshadweep islands, remaining parts of Uttar Pradesh, Gujarat and West Bengal, Parts of Punjab, Rajasthan, Madhya Pradesh, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Orissa, Andhra Pradesh, Tamilnadu and Karnataka.
• Seismic Zone IV: Major damage corresponding to intensity VII and higher of MM scale. It covers remaining parts of Jammu and Kashmir and Himachal Pradesh, National Capital Territory (NCT) of Delhi, Sikkim, Northern Parts of Uttar Pradesh, Bihar and West Bengal, parts of Gujarat and small portions of Maharashtra near the west coast and Rajasthan.
• Seismic Zone V: Area determines by pro seismically of certain major fault systems. It is seismically the most active region, and comprises entire northeastern India, parts of Jammu and Kashmir, Himachal Pradesh, Uttaranchal, Rann of Kutch in Gujarat, part of North Bihar and Andaman & Nicobar Islands.

How vulnerable is Mizoram to earthquake?

• Mizoram is one of the North Eastern States of India, located in 21º56' and 24º31' N latitude and 92º16' and 93 º 26’ E longitudes with the geographical area of 21,081 sq. km.
• Mizoram is vulnerable to all-major natural hazards such as Cyclone, Earthquake, and Landslide etc.
• The State forms a part of the most severe seismic zone in the country, namely Zone V of Seismic Zone Map of India that is referred as Very High Damage Risk Zone.
• The seismic risk in the region is growing at an alarming pace with increasing inventory of vulnerable construction.