Table of Contents:
- What are earthquakes
- Major Earthquake of India
- Types of Earthquake
- Earthquake Zones of India
- The consequence of the earthquake
- Earthquake Preparedness
- Differentiate between the "intensity" and "magnitude" of an earthquake and explain its varying impact in different parts of India. (UPSC 2014, 200 words, 15 Marks)
- Describe the earthquake belts in India. ( UPPSC 2022)
What are earthquakes?
Earthquake simply means vibration on the earth's surface and it is often caused by the movement of lithospheric plates but it can be man-made.
An earthquake is a sudden endogenous force also called the constructive force of landform development.
It is also a natural hazard as the release of energy from the focus of the earthquake causes huge damage to human life and property.
As of now, we do not have the technology to predict earthquakes; One can predict earthquakes to some extent by studying animal behavior and using some conventional wisdom.
For example,
When an earthquake occurs, the fish in the ponds get excited and the snakes move out of their burrows.
Some important facts:
Tectonic Earthquakes:
- The place from where the wave starts is called the focus (center of origin).
- The place closest to the focus on the ground surface is called the epicenter.
- The greatest damage is usually close to the epicenter and the strength of the wave decreases with increasing distance from the epicenter.
Some major recent earthquakes in India:
- Earthquake on 26 January 2001 at Bhuj in Gujarat.
- 8 October 2005, Uri and Tangdhar towns of North Kashmir.
Types of earthquakes:
Tectonic earthquakes are caused by the movement of tectonic plates.
Volcano Earthquakes:
- A volcanic earthquake is caused by a volcanic eruption.
- Underground mines collapse due to intensive mining activities and the earthquake generated by this type of activity is called a collapse earthquake.
- Earthquakes are also generated by the explosion of chemical and nuclear equipment.
- An earthquake caused by the rupture of a large dam or the breaking of the plates below it by the weight of its water is called a reservoir-induced earthquake.
Distribution of earthquakes in India:
 |
| Earthquakes zone in India. |
Initially, the Bureau of Indian Standards (BIS) divided the country into five seismic zones, but after the 1993 Killari /Latur earthquake in Maharashtra, Zone 1 was changed to Zone II, and now India has four seismic zones.
Zone V :
- This is the region of the highest-intensity earthquake zones.
- This region includes Jammu and Kashmir and a small part of Himachal Pradesh, the northern part of Uttarakhand, northern Bihar, northeast India, the Kutch region of Gujarat, and Andaman and the Nicobar Islands.
Zone IV:
- This is a severe earthquake zone. It is the area around Zone V which includes Jammu and Kashmir, Himachal Pradesh, Delhi, Sikkim, Goa, a small part of West Bengal, and part of Gujarat.
Zone-III:
- This is a moderately intense earthquake zone.
- It includes Lakshadweep, Kerala, part of Tamil Nadu, Karnataka, Maharashtra, part of Andhra Pradesh, and Telangana, Central India.
Zone-II:
- This is a less dense area.
- It includes the Karnataka plateau, part of Rajasthan, and Odisha.
The consequence of the earthquake:
The following are the consequences of the earthquake:
- Earthquakes destroy natural and cultural landscapes and create new landforms.
- A dam break can cause flooding.
- If earthquakes occur in the ocean, then the risk of tsunamis increases.
- Landslides happen.
- Fire occurs.
- Soil liquidation occurs.
- Life and economic loss.
If well prepared, the impact of earthquakes can be minimized.
There are three levels of preparation:
- Preventive preparation
- During an earthquake
- After the earthquake
Preventive preparation;
- Being aware of earthquakes
- To build earthquake-resilient infrastructure and buildings.
During an earthquake;
- Stay away from fire, chimneys, electric wires, windows, glass, etc.
- Finding a safe place under the kitchen counter or table.
After the earthquake;
- Rapid response and search operations and increasing the availability of medicines, food, clothing, and water.
Question.
Differentiate between the "intensity" and "magnitude" of an earthquake and explain its varying impact in different parts of India.
(UPSC 2014, 200 words, 15 Marks)
Answer.
The "intensity" and "magnitude" of an earthquake are distinct but related scales that describe different aspects of seismic events:
Magnitude:
Magnitude measures the energy released at the earthquake's source. It is typically quantified using the Richter scale or the moment magnitude scale (Mw).
It is a logarithmic scale, meaning that each whole number increase on the scale represents a tenfold increase in amplitude of seismic waves and approximately 31.6 times more energy release.
In India, earthquakes with higher magnitudes are less frequent but can have devastating effects, especially in regions near tectonic plate boundaries, like the Himalayan region.
Intensity:
Intensity measures the effects of an earthquake at a specific location. It assesses the level of shaking and damage experienced at the Earth's surface.
Intensity is typically described using the Modified Mercalli Intensity (MMI) scale, which ranges from I (not felt) to XII (total destruction).
Intensity values can vary significantly from one location to another, even for the same earthquake, depending on factors like distance from the epicenter, local geology, and building construction.
India's varied geological and geophysical conditions result in varying intensities across the country.
The varying impact of earthquakes in different parts of India can be explained as follows:
Himalayan Region:
The northern part of India, including states like Jammu and Kashmir, Himachal Pradesh, and Uttarakhand, is prone to large-magnitude earthquakes due to the collision of the Indian and Eurasian tectonic plates.
Earthquakes in this region tend to have both high magnitude and intensity, resulting in significant damage and casualties.
North-Eastern Region:
The northeastern states of India, including Assam, Arunachal Pradesh, and Manipur, are also seismically active due to tectonic plate interactions.
Earthquakes in this region can vary in magnitude and intensity, impacting local communities and infrastructure.
Peninsular India:
The southern and central parts of India experience relatively lower seismic activity compared to the Himalayan and northeastern regions.
Earthquakes in this area generally have lower magnitudes and intensities, causing less damage.
Coastal Regions:
Coastal areas, especially in the western and eastern parts of India, may experience tsunamis triggered by Ocean earthquakes. These events can have catastrophic consequences.
In summary, India's diverse geography results in varying earthquake magnitudes and intensities across the country. Understanding these differences is crucial for earthquake preparedness, mitigation, and infrastructure development in different regions.
Question.
Describe the earthquake belts in India.
(UPPSC Mains General Studies-I/GS- 2022)
Answer.
India is seismically active due to its position near the convergent boundary of the Indian Plate and the Eurasian Plate. As a result, there are several earthquake-prone zones or belts in India.
Here are the main earthquake belts in the country:
Himalayan Seismic Belt:
The Himalayan Seismic Belt is the most prominent earthquake belt in India and extends along the entire length of the Himalayan mountain range.
The earthquakes in this belt are primarily caused by the ongoing collision between the Indian Plate and the Eurasian Plate. The Indian Plate is moving northward and is being forced beneath the Eurasian Plate, leading to intense tectonic activity.
Indo-Gangetic Plain and Northern Plains Seismic Belt:
This belt includes the northern plains of India, particularly the Indo-Gangetic Plain.
While the seismic activity in this belt is related to the broader collision between the Indian Plate and the Eurasian Plate, it is less intense compared to the Himalayan Seismic Belt. The earthquakes here are often associated with the reactivation of ancient fault lines.
Eastern Seismic Zone:
This zone covers parts of eastern India, including West Bengal, Bihar, and northeastern states.
The Eastern Seismic Zone is associated with the complex tectonics of the Indian Plate interacting with the Burmese Plate and the Indo-Australian Plate. Subduction zones and plate boundary faults are present in this region.
Andaman and Nicobar Islands Seismic Zone:
This zone includes the Andaman and Nicobar Islands in the Bay of Bengal.
The earthquakes in this region are mainly due to the subduction of the Indian Plate beneath the Burma Plate along the Andaman-Sumatra Trench. The region is also susceptible to tsunamis triggered by undersea earthquakes.
"Rann of Kachchh" Seismic Zone:
This zone covers the Rann of Kachchh area in Gujarat.
Similar to the Kutch Seismic Belt, this region experiences earthquakes related to the movement of the Indian Plate against the Arabian Plate.
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