Earthquake

Mains Marks Booster     5th August 2023        
Samadhaan

An earthquake is a violent and abrupt shaking of the ground, caused by movement between tectonic plates along a fault line in the earth's crust. Earthquakes can result in ground shaking, soil liquefaction, landslides, fissures, avalanches, fires, and tsunamis.


  • Of the earthquake-prone areas,12% are prone to very severe and 18% to severe earthquakes, and  25% to damageable earthquakes.
  • Economic cost - in the case of Latur ,Bhuj and Sikkim earthquakes the loss percentage is 0.13% ,1%, and 0.13% of GDP.
  • Himalayan regions and Andaman, Nicobar, Himachal, and north east are prone to earthquakes.

  • Focus and Epicentre: The initial point of energy release is the focus, and the surface point above it is the epicenter.
  • Foreshocks and Aftershocks: Major earthquakes often involve minor aftershocks and sometimes have preceding foreshocks.
  • Swarms: Clusters of small earthquakes are called swarms and often indicate impending volcanic activity.

Causes of Earthquakes

  • Fault Zones: Most shallow earthquakes result from stress release along fault ruptures in the earth's crust.
  • Plate Tectonics: Earthquakes can occur due to slipping of land along fault lines in convergent, divergent, and transform boundaries.
  • Volcanic Activity: Less severe earthquakes can be caused by volcanic activity, which can serve as early warning signs of eruptions.
  • Human-Induced Activity: Human activities like mining or reservoir construction can cause minor earthquakes.

Focus Depth of Earthquakes

  • Shallow Focus: Shallow earthquakes occur at depths of 0-70 km.
  • Intermediate Focus: These earthquakes occur at depths of 70-300 km.
  • Deep Focus: Deep-focus earthquakes occur at depths of 300-700 km.

Distribution of Earthquakes

  • Circum-Pacific Belt: This is the major earthquake belt, affecting coastal regions around the Pacific Ocean.
  • Alpine Belt: A significant belt of seismic activity that includes the Himalayas and Alps.
  • Oceanic Ridges and Rift Valleys: Seismic activity also occurs along oceanic ridges and rift valleys in the Arctic Ocean, Atlantic Ocean, western Indian Ocean, and East Africa.

Impact of the Earthquake:


Impact of Earthquakes

Description

Shaking and Ground Rupture

Damage to rigid structures, major risk to large engineering structures.

Landslides and Avalanches

Can result from earthquakes, causing slope instability.

Fires

Caused by damage to electrical power or gas lines; can result in more fatalities than the quake itself.

Soil Liquefaction

Transforms water-saturated soil from solid to liquid, causing structures to tilt or sink.

Tsunami

Megathrust quakes can move large water volumes, producing long-wavelength, long-period sea waves.

Floods

Secondary effects of earthquakes due to dam damage or landslips that dam rivers.



Seismic Zoning Map:

 Seismic Zoning Map

NDMA Guidelines for Earthquakes:

  • Earthquake-Resistant Design and Construction of New Structures: Encourage the building of earthquake-resistant structures in seismic-prone areas, ensuring strict adherence to regulations and building codes. This includes educating future engineers and architects about these techniques.
  • Seismic Strengthening and Retrofitting of Lifeline and Priority Structures: Perform a structural safety audit and retrofit select critical lifeline structures and high-priority buildings in seismic Zones III, IV, and V, based on risk, potential loss of life, and financial implications.
  • Regulation and Enforcement: Periodically revise the codes and standards related to earthquake-resistant construction to keep up with international practices. Ensure codes developed by other regulatory bodies are updated with current state-of-the-art techniques.
  • Awareness and Preparedness: Implement a comprehensive awareness campaign to educate the public about safe practices before, during, and after an earthquake, emphasizing the seismic risk and vulnerability of the states.
  • Creation of Public Awareness on Seismic Safety and Risk Reduction: Develop and distribute educational materials such as a handbook on earthquake safety, a homeowner's seismic safety manual, and a manual on structural safety audit of infrastructure. Create videos and translate these resources into regional languages for wider reach.
  • Capacity Development (Including Education, Training, R&D, and Documentation: Improve the quality of education materials, field training, and teaching at all levels, focusing on capacity and skills development. Encourage research, teaching, and training that contribute to improving earthquake education in India.
  • Response: Develop coordinated, prompt, and effective response systems at the district and community levels. Consider the multi-hazard scenario of various regions to optimally utilize resources and strengthen emergency response capabilities.

Challenges in India’s Preparedness for Earthquakes:

  • Retrofitting in hilly and mountainous areas, which constitute the majority of earthquake-prone zones, is both challenging and costly.
  • There's a significant deficit of skilled labor proficient in designing and building structures that can withstand earthquakes.
  • A competency-based licensing system for structural engineers is not yet formally established.
  • Compliance with building codes is lax, leading to a disregard for necessary safety requirements.
  • As per NDMA, nearly 4,000 multistory buildings in Ahmedabad may not survive a severe earthquake due to inferior design.
  • The mechanism for fund collection during disasters lacks standardization, and awareness about the national disaster relief fund is insufficient.
  • The flood response coordination in Uttarakhand exposed deficiencies in the disaster response system.
  • Current efforts to generate awareness and train local communities for post-disaster operations are inadequate.

Prevention and Mitigation of Earthquakes: 

Long-term measures:

  • Re-framing buildings' codes, guidelines, manuals, and bylaws and their strict implementation. 
  • Incorporating earthquake-resistant features in all buildings in high-risk areas.
  • Constructing earthquake-resistant community buildings, especially in seismic zones of moderate to higher intensities.
  • Supporting R&D in various aspects of disaster mitigation, preparedness and prevention, and post-disaster management.

Medium-term measures:

  • Retrofitting of weak structures in highly seismic zones.
  • Preparation of disaster-related literature in local languages with dos and don'ts for construction.
  • Getting communities involved in the process of disaster mitigation through education and awareness.
  • Networking of local NGOs working in the area of disaster management.

Important institution to prevent and mitigate earthquake loss

  • National Centre for Seismology for earthquake preparedness
  • National earthquake risk mitigation project
  • National building code 
  • National retrofit program for India's earthquake preparedness.
  • Mobile apps - Sagar Vani (alert and information)India quake (National Centre for Seismology disseminates information)

Conclusion:

Earthquake vulnerabilities can be reduced due to integrated approaches at international, national, and local levels. Education to people about earthquake safety and preparedness, including how to evacuate safely and what to do during an earthquake is essential. With this Implement early warning systems that can alert people of an impending earthquake, giving them time to evacuate or take other safety measures. And at last Develop emergency response plans that outline the actions to be taken in case of an earthquake, including evacuation procedures and contingency plans for power restoration and other critical infrastructure.

Samadhaan