Earthquakes: Nature’s Powerful Forces

Earthquakes are natural phenomena characterized by the sudden release of energy in the Earth’s crust, leading to seismic waves. While earthquakes are essential in shaping the Earth’s landscape, they can also pose significant threats to human communities, emphasizing the importance of preparedness and resilient infrastructure.

Understanding Earthquakes: Tremors, Origins, and Impacts

• Meaning: A sudden shake or trembling of the earth which lasts for a very short time is referred to as an earthquake.
• Focus: The point inside the earth where the earthquake starts is the focus point.
• Epicenter: It is the point on the surface of the earth above the focus point.
• They may also cause floods, landslides, tsunamis, and loss of life.

Causes of Earthquakes: Deep Disturbances, Plate Dynamics, and Varied Triggers

• Deep Disturbances: It is caused by a disturbance deep inside the earth’s crust.
• The outer layer of the earth is fragmented.
• Plate: Each fragment is called a plate. 
• Continuation Motion: These plates are in continual motion, so when they brush past one another, or a plate goes under another due to collision, they cause disturbance in the earth’s crust.
  • It is this disturbance that shows up as an earthquake on the surface of the earth.
• Different Causes: The other causes are volcanic eruptions, meteor hits, and nuclear explosions.

Earthquakes: Seismic or Fault Zones

• The boundaries of the plates are the weak zones where it is more likely to occur. 
• The weak zones are also known as seismic or fault zones.

Earthquakes: Seismic or Fault Zones in India

In India, the most threatened areas are as follows:

• Kashmir
• Western and Central Himalayas
• Rann of Kutch
• The whole of North-East
• Rajasthan and the Indo-Gangetic Plain
• Some areas of South India 

Measurement of Earthquake: Insights into Seismographs and the Richter Scale

• Seismograph: It is an instrument used to detect and record earthquakes.
  • ​​It consists of a metal rod attached to a fixed base.
  • During an earthquake, the base moves, but the rod does not move. 
  • The movement of the base to the rod is commonly transformed into an electrical voltage.
  • This record is proportional to the motion of the metal rod relative to the earth, but one can convert it to a record of the absolute motion of the ground.
• Richter scale: The power of an earthquake is expressed in terms of a magnitude on a scale called Richter scale.
  • Destructive earthquakes have magnitudes higher than 7 on the Richter scale.
  • Both Bhuj and Kashmir earthquakes had magnitudes greater than 7.5. 

Protection Against Earthquake: Essential Measures for Seismic Safety

• Precautionary Measure: Since we know that these cannot be predicted and are highly destructive, therefore, it is important that we take necessary precautions to protect ourselves all the time. 
• Special Preparedness: People living in seismic zones, where the earthquakes are more likely to occur, have to be specially prepared. 
  • First of all, the buildings in these zones should be designed so that they can withstand major tremors. 
  • Modern building technology can make it possible.
  • It is advisable to make the structure simple so that it is ‘Quake Safe’.
• Use of different Materials: In highly seismic areas, the use of mud or timber is better than the heavy construction material. 
• Fire Safety: Since some buildings may catch fire due to an earthquake, it is necessary that all buildings, especially tall buildings, have fire fighting equipment in working order.
• Research and Development: The Central Building Research Institute, Roorkee, has developed knowhow to make quake proof houses.