Earthquake in Himalayas Region

Syllabus: GS1/ Geography

Context 

• Recently a strong earthquake with a magnitude of 7.1 struck in western China near Nepal.

About

• The epicenter of the earthquake was identified in Tingry County in the Shigatse region of Tibet, a significant location as it serves as a ‘gateway’ to Mount Everest. 
• The earthquake’s mainshock likely occurred within the Lhasa terrane, a distinct crustal fragment involved in major hydroelectric projects, including the world’s largest hydroelectric dam under construction by China.

What is an Earthquake? 

• An earthquake is the shaking of the ground caused by movement beneath the earth’s surface when two blocks slip past each other along a fault. 
• This sudden movement releases stored elastic strain energy in the form of seismic waves, which causes ground shaking. 
• Epicentre and Hypocenter: The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.
• Earthquakes are measured using the Richter scale for magnitude and the Mercalli scale for intensity based on visible damage.

Foreshocks and Aftershocks

• Foreshocks: These are smaller earthquakes that happen in the same place as the larger earthquake that follows.
  • The largest, main earthquake is called the mainshock.
• Aftershocks: These are smaller earthquakes that occur afterwards in the same place as the mainshock. 

Measuring Earthquakes

• The earthquake events are scaled either according to the magnitude or intensity of the shock.
• Richter Scale: Measures small to medium earthquakes based on seismic wave amplitude.
• The intensity scale, named after Mercalli, considers the visible damage caused by the event.

Seismic Waves

• Seismic waves are energy waves generated by an earthquake that travels through the Earth’s layers, causing ground shaking. 
• They are mainly classified into two types: body waves and surface waves.
  • Body Waves:These waves travel through the interior of the Earth. They are faster and arrive before surface waves during an earthquake. 
  • Surface waves travel along the Earth’s surface and are slower than body waves but cause the most damage due to their larger amplitude. 

Types of Body Waves

• P-Waves (Primary Waves): They are the fastest seismic waves and the first to be recorded by seismographs. They move in a compressional or longitudinal manner.
  • P-waves can travel through solids, liquids, and gases.
• S-Waves (Secondary Waves): They move in a transverse manner, where particles move perpendicular to the wave’s direction of propagation.
  • S-waves can travel only through solids, as liquids and gases do not support shear stress.

Reason of Earthquake in Himalayas

• Around 50 million years ago, the Indian plate collided with the Eurasian plate, causing rocks to fold and rise to create the Himalayas Mountains.
• The tension between the two plates has continued to build as the Indian plate is still pushing in at around 60 mm/year. 
• Earthquakes and tremors occur when the rock formations in the region shift ever so slightly as they adjust to the tension.

Impacts of Earthquake in Himalayas

• Tectonic Activity: The region lies along the convergence zone of the Indian and Eurasian plates.
  • The area remains seismically active due to continuous plate movement, which contributes to frequent earthquakes.
• Hydrological Significance: The broader Himalayan region is known as the ‘Third Pole’ due to its vast reserves of water stored in glaciers, lakes, and rivers.
  • Earthquakes can destabilize glaciers, alter river courses, and heighten flood risks, threatening millions who rely on Himalayan water sources.
• Strategic and Infrastructural Importance: Earthquakes in such areas could impact major energy generation projects and raise safety concerns.

Source: TH