There are three basic types of seismic waves –
(1) Primary Waves (P-wave) – they are similar to sound waves. They are also known as longitudinal waves. P-Waves travel faster than any other waves. Their intensity of travel depends upon the density of the rock they encounter.
Since they are the fastest travelling seismic wave, hence are the first signal from an earthquake to arrive at any affected location or at a seismograph. P–waves may be transmitted through gases, liquids or solids.
(2) Secondary Waves (S-wave) – they are similar to light waves. They are also known as Transverse waves. These waves arrive after the primary waves and travel slower than
the P-Waves. The S-waves can travel only through solid materials.
(3) Surface Waves or L Wave – these waves travel slower than the other two waves and can travel only through the crust of the earth. Surface waves travel around the globe
before reaching the epicentre. Surface waves are the most damaging of all the waves.
