The earthquake events are scaled either according to the magnitude or intensity of the shock. An earthquake in simple words is the shaking of the earth. It is a natural event. It is causes due to release of energy, which generates waves that travel in all directions.

• National Geophysical Laboratory, Geological Survey of India has divided India into the following five earthquake zones:
  • Very high damage risk zone
  • High damage risk zone
  • Moderate damage risk zone
  • Low damage risk zone
  • Very low damage risk zone

Measuring earthquakes

• Seismometers are the instruments which are used to measure the motion of the ground, which including those of seismic waves generates by earthquakes, volcanic eruptions, and other seismic sources.
• A Seismograph is also another term used to mean seismometer though it is more applicable to the older instruments.
• The recorded graphical output from a seismometer/seismograph is known as a seismogram. (*Do not confuse seismograph with seismogram. Seismograph is an instrument while seismogram is the recorded output*)
• There are two main scales used in the seismometers: (1) Mercalli Scale and (2)Richter Scale.

1) Mercalli Scale:

The scale represents the intensity of earthquake by analyzing the after effects like how many people felt it, how much destruction occurred etc. The range of intensity is from 1-12.

2) Richter Scale:

The scale represents the magnitude of the earthquake. The magnitude is express in absolute numbers from 1-10. Each whole number increase in Richter scale represents a ten times increase in power of an earthquake.

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