Why is the Himalayan region seismically active?

Why in the NEWS?

• Earthquake of 7.1 magnitude hits Tibet, hundreds of people killed, tremors felt in India from Bihar to Bengal.

Key Points:

• On January 7, an earthquake measuring about 7 on the Richter scale struck Tibet, killing about 100 people and damaging about 1,000 houses.
• The epicentre of the earthquake was in Shigatse city of Tibet, 93 km northeast of Lobuche in Nepal.

What are the causes of most earthquakes in Tibet and Himalayan region?

• The main reason that makes Tibet and Himalayan region one of the most earthquake-prone regions of the world is the geological structure and the mobility of tectonic plates.
• The Himalayan mountain range began to form about 40 to 50 million years ago when the Eurasian and Indian plates first began to collide with each other.
• Since both plates were of similar density, the land at their point of collision rose up.
• Over time, the continued pull of the Eurasian plate caused it to sub duct, i.e., it moved beneath the Indian plate. This process continues today.
• Seismicity in the Himalaya is caused primarily by the continental collision of the India and Eurasia plates, which are converging at a relative rate of 40–50 mm/year.
• Collision of tectonic plates:
  • The collision of Indian plate and Eurasian plate causes high seismic activity in this region. 
  • The Indian plate is moving in the north direction and colliding with the Eurasian plate, which creates geological stress. 
  • This stress is ultimately felt on the surface of the earth in the form of earthquakes.
  • This collision also gives rise to the high mountain ranges of Himalayas and this makes this region highly vulnerable to earthquakes.
• Fault lines:
  • Several major fault lines exist in this region, such as the Dhaulagiri fault and the Indus-Ganga fault, which can become the epicentres of earthquakes.
  • These fault lines absorb the stress generated by the collision of plates, and when this stress is suddenly released, earthquakes occur.
  • Driven friction and movement of plates:
  • The friction between the Indian plate and the Eurasian plate and the movement between them causes an increasing state of stress. 
  • When this stress reaches a limit, it is released on the surface of the earth in the form of an earthquake.
• Geological activity of the Himalayan region:
  • The presence of the Himalayan mountain range also makes this region earthquake-prone, as the region is constantly in the process of geological movement and construction. 
  • Seismic movements also occur when mountains and valleys are formed here.
• Frequency of earthquakes in history:
  • As reported by the United States Geological Survey, in the last few decades, there have been several earthquakes in this region with a magnitude of 6 or more. 
  • This regular seismic activity indicates that this region is an active seismic zone.
• Seismic impact of Mount Everest and surrounding region:
  • Mount Everest and its surrounding area, which is a part of the Himalayas, is extremely sensitive from the seismic point of view, as the region is located at the boundary of the Indian and Eurasian plates.

Future earthquake risk

• The western Himalaya is one of the world's most dangerous seismic regions. 
• Scientists have long said that a major earthquake of magnitude greater than 8 is imminent across a vast region stretching 2,500 kilometres from the Hindu Kush to Arunachal Pradesh. 
• The constant interaction of tectonic plates causes a lot of energy to be stored along fault lines – which can only be released in the form of a large earthquake.
• A 2017 study ('Implications for elastic energy storage in the Himalaya from the Gorkha 2015 earthquake and other incomplete ruptures of the Main Himalayan Thrust') published in Quaternary International found that only two Himalayan earthquakes have ruptured at the surface in the past 500 years.