Question

Explain the types of seismic waves.

Answer 1

During an earthquake, accumulated tension is released in massive waves to cause the trembling at the surface of the earth. These waves are called seismic waves and are of three types –

1. Primary Seismic Waves or P waves:
   • The waves that reach the earth’s surface first once energy is emitted from the earth’s surface are called primary seismic waves.
   • These waves can travel through all the three mediums of liquid, solid and gaseous states.
   • They have high velocity and move in a radial direction from the focus of the earthquake.
   • These waves are often called forward-backward waves as particles through which these waves pass tend to move to and fro in the direction of the waves.
   • Initial waves are felt but are not damaging to a great extent.
2. Secondary Seismic Waves or S waves:
   
   • The waves that reach the earth’s surface after the primary waves once energy is emitted from the earth’s surface are called secondary seismic waves.
   • These waves can travel through only solid state medium and get absorbed in any liquid state mediums.
   • They have lower velocity than Primary waves and scatter in all directions from the earthquake focus point.
   • These waves cause the particles it passes through to move up and down.
   • These waves are more damaging causing the maximum destruction during an earthquake.
3. Surface seismic waves or L waves:
   
   • These waves are generated after the main P and S waves reach the epicenter.
   • They travel in the direction of the circumference of the earth along the crust.
   • They are highly destructive.