Earthquakes: Sudden Shaking, Destructive Forces, Varied Magnitude

Earthquake refers to the sudden shaking of the earth’s crust. It is highly destructive of all the natural disasters. They occur when there is a rupture in the Earth’s surface, typically along a fault line, leading to seismic waves that propagate through the ground. 

The intensity and magnitude of the temblor vary, causing shaking and trembling of the ground.

Key points about earthquakes: Causes, Measurement, and Intensity Scales

• Causes of Earthquakes:  Earthquakes result from a series of earth movements brought about by a sudden release of energy during the tectonic activities in the earth’s crust.
• Earthquakes due to other causes: It could also be triggered by volcanic eruption, rock falls, landslides, subsidence, particularly in the mining areas, impounding of dams and reservoirs, etc. 

• Measuring Earthquakes: Temblor can be measured by the use of two distinctively different scales of measurement demonstrating magnitude and
• Richter Scale: Temblor magnitude is determined by the use of a seismograph, which is an instrument that continuously records ground vibration. 

List of Significant Earthquakes in India

• The scale was developed by a seismologist named Charles Richter, so-called the Richter Scale.
• Mercalli Scale: The second type of scale, the temblor intensity scale measures the effects of a temblor where it occurs and was developed in 1902 by Mercalli, an Italian seismologist. 
  • Hence this scale is called the Mercalli scale.
• Understanding Earthquake Intensity: Mercalli Scale expresses the intensity of a temblor effect on people, structure and the earth’s surface in values from I to XII.
  • Intensity of VI and below: People can feel the shake and there are cracks in the walls.
  • Intensity of XII: General panic with buildings collapsing totally and there is a total disruption in normal life.

Distribution Pattern of Earthquakes in India: Assessing Risk and Safety Levels

• The seismic zoning map of India is divided into the following five temblor zones:

1. Very high damage risk zone
2. High damage risk zone
3. Moderate damage risk zone
4. Low damage risk zone
5. Very low damage risk zone.

• Very high damage risk zone: This zone includes,
  • North-east states, areas to the north of Darbhanga and Araria along the Indo-Nepal border in Bihar.
  • Uttarakhand, Western Himachal Pradesh (around Dharamshala) and Kashmir Valley in the Himalayan region and the Kachchh (Gujarat).

• High damage risk zone: This zone include, 
  • Parts of Jammu and Kashmir, Ladakh, Himachal Pradesh, Northern parts of Punjab, Eastern parts of Haryana, Delhi, Western Uttar Pradesh, and Northern Bihar. 
• Moderate to Very Low Damage Risk Zone: Remaining parts of the country fall under moderate to very Low Damage Risk Zone. 
  • Most of the areas of the Deccan plateau are considered safe as far as temblor are concerned.

Earthquake Hazard Zones in India

Consequences of Earthquakes: Impact on People, Infrastructure, and Environment

• Terrifying Tremors: Temblor is often associated with fear and horror due to the scale, magnitude and suddenness at which it spreads disasters on the surface of the earth. 
  • It becomes a calamity when it strikes the areas of high density of population. 
• Devastating Impact: It damages and destroys the settlements, infrastructure, transport and communication network, industries and other developmental activities.
  • It robs the population of the material and socio-cultural gains that they have preserved over generations. 
  • It renders people homeless, which puts pressure and stress, particularly on the weak economy of developing countries.
  • It also causes fires, dam failure and landslides which may block waterways and also cause flooding. 
• Crippling Consequences: It may damage manufacturing industries and break down communication facilities. 
  • There is also a huge loss to the public health system, transport, communication and water supply in the affected areas.

• Surface seismic waves produce fissures on the upper layers of the earth’s crust through which water and other volatile materials gush out, inundating the neighbouring areas. 

Earthquake Hazard Mitigation: Preparedness, Resilience, and Community Empowerment

• Earthquake Preparedness: It is not possible to prevent the occurrence of a temblor. Hence, the next best option is to emphasise disaster preparedness and mitigation rather than curative measures such as:
  • Strengthening Earthquake Preparedness: Monitoring, Mapping, and Informing
    • Establishing temblor monitoring centres (seismological centres) for regular monitoring and fast dissemination of information among the people in the vulnerable areas. 
    • Use of Geographical Positioning System (GPS) can be of great help in monitoring the movement of tectonic plates.
    • Preparing a vulnerability map of the country and dissemination of vulnerability risk information among the people.
• Disaster Resilience Strategies: Community Empowerment and Safer Construction
  • Empowering Communities: Educating people about the ways and means of minimising the adverse impacts of disasters.
  • Adaptive Architecture and Urban Planning: Modifying the house types and building designs in the vulnerable areas and discouraging the construction of highrise buildings, large industrial establishments and big urban centres in such areas.
    • Making it mandatory to adopt earthquake-resistant designs and use of light materials in major construction activities in vulnerable areas.
• Essential Knowledge: Thus, Understanding temblors and their impact is vital for both scientific study and for implementing strategies to mitigate the damage caused by these natural disasters.

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