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Delhi Earthquake: Causes, Seismic Zones, and Preparedness

 

Delhi Earthquake: Causes, Seismic Zones, and Preparedness



Context: A 4.0-magnitude earthquake struck Delhi-NCR, with its epicenter at Dhaula Kuan. The tremors were felt across the region, raising concerns about Delhi's vulnerability to seismic activity.

What Are Earthquakes?

An earthquake is a sudden release of energy in the Earth's crust that generates seismic waves, causing ground shaking. Earthquakes occur due to the movement of tectonic plates along fault lines.

Key Causes of Earthquakes:

  1. Tectonic Plate Movement: The Earth's lithosphere is divided into plates that constantly move. When they collide, slide past each other, or diverge, stress builds up along fault lines.
  2. Sudden Release of Energy: When accumulated stress exceeds the rock’s capacity to withstand it, the energy is released, causing seismic waves and ground shaking.

Shallow Earthquakes:

  • Depth: These earthquakes occur close to the Earth's surface (typically 5-10 km deep).
  • Impact: Due to their proximity to the surface, shallow earthquakes cause more damage than deeper ones.

Reasons Behind the Delhi Earthquake

Delhi’s vulnerability to earthquakes is linked to its location near multiple fault lines.

  1. Seismic Faults:

    • Delhi-Hardwar Ridge: A significant tectonic structure running through Delhi, known for moderate seismic activity.
    • Mahendragarh-Dehradun Fault: Another active fault line contributing to Delhi’s earthquake risk.

  2. Tectonic Stress:

    • The tremors result from stress accumulation along these fault lines. When the stress is suddenly released, seismic waves are generated, causing ground shaking.

  3. Soil Composition:

    • Soft Alluvial Soil: Some areas in Delhi have soft alluvial soil, which amplifies seismic waves. This amplification can lead to more intense shaking and potential structural damage.

India’s Earthquake Zoning System

India’s seismic zoning map classifies the country into four seismic zones based on the risk of earthquakes.

Seismic Zones in India:

  1. Zone 5:

    • Description: Highest seismic risk.
    • Examples: Himalayan region, Northeastern states, Andaman and Nicobar Islands.

  2. Zone 4:

    • Description: High risk of earthquakes.
    • Examples: Delhi, Jammu & Kashmir, Bihar.

  3. Zone 3:

    • Description: Moderate risk zone.
    • Examples: Mumbai, Chennai, Kolkata.

  4. Zone 2:

    • Description: Low risk of seismic activity.
    • Examples: Deccan Plateau.

Delhi is classified under Seismic Zone 4, indicating a high susceptibility to earthquakes and the need for adequate disaster preparedness measures.

How Are Earthquakes Measured?

Several scales are used globally to measure the magnitude and intensity of earthquakes:

  1. Richter Scale:

    • Purpose: Measures the magnitude or total energy released by an earthquake.
    • Logarithmic Nature: Each whole-number increase represents 10 times stronger shaking and 32 times more energy release.

  2. Modified Mercalli Scale (MMS):

    • Purpose: Measures the intensity of the earthquake based on the shaking and damage experienced.
    • Scale Range: Ranges from 1 (Not Felt) to 12 (Total Destruction).

  3. Medvedev-Sponheuer-Karnik (MSK) Scale:

    • Widely used in India’s seismic hazard assessments to estimate potential earthquake damage.
    • Useful for planning disaster response and designing earthquake-resistant structures.

Why Delhi Needs Earthquake Preparedness

Given its classification under Seismic Zone 4, Delhi is highly vulnerable to earthquakes. Effective disaster management, urban planning, and public awareness are critical to mitigating the risks.

Key Measures to Improve Preparedness:

  1. Earthquake-Resistant Construction:

    • Buildings should be constructed or retrofitted to withstand seismic activity.

  2. Public Awareness Campaigns:

    • Educating the public on earthquake safety measures, such as identifying safe spaces and preparing emergency kits.

  3. Disaster Management Plans:

    • Strengthening the coordination between local authorities, hospitals, and disaster response teams.

  4. Early Warning Systems:

    • Implementing technology to detect seismic activity early and issue warnings.

Conclusion

The 4.0-magnitude earthquake in Delhi is a stark reminder of the region’s seismic vulnerability. By understanding the causes, risks, and measurement of earthquakes, authorities and citizens can take proactive measures to improve earthquake preparedness and ensure public safety.

MCQs for UPSC CSE Based on Delhi Earthquake

1. Which fault line contributes to seismic activity in the Delhi region?
a) San Andreas Fault
b) Mahendragarh-Dehradun Fault
c) East Anatolian Fault
d) Himalayan Thrust Fault

Answer: b) Mahendragarh-Dehradun Fault

2. What is the highest seismic risk zone according to India’s seismic zoning map?
a) Zone 2
b) Zone 3
c) Zone 4
d) Zone 5

Answer: d) Zone 5

3. Which soil type amplifies seismic waves, leading to increased shaking in Delhi?
a) Rocky soil
b) Sandy soil
c) Alluvial soil
d) Loamy soil

Answer: c) Alluvial soil

4. Which scale measures the magnitude of an earthquake?
a) Modified Mercalli Scale
b) Richter Scale
c) Beaufort Scale
d) Fujita Scale

Answer: b) Richter Scale

5. Delhi is classified under which seismic zone in India?
a) Zone 2
b) Zone 3
c) Zone 4
d) Zone 5

Answer: c) Zone 4

Mains Question for UPSC CSE

"India’s capital, Delhi, falls under Seismic Zone 4. Discuss the causes behind the seismic vulnerability of Delhi and suggest measures to improve earthquake preparedness and disaster resilience in the region."

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