Seismic Waves

Explanation :

P-waves

• These are the first waves detected by seismographs (instruments used to detect and record earthquakes).
• These are longitudinal waves which means they vibrate along the same direction as they travel.
• Examples of longitudinal waves include sound waves and waves in a stretched spring.

S-waves

• These waves arrive at the detector after primary waves.
• These are transverse waves which means they vibrate at a right angle to the direction in which they travel.
• Examples of transverse waves include light waves and water waves.

Difference

• Both types of seismic waves can be detected near the earthquake centre but only P-waves can be detected on the other side of the Earth.
• P-waves can travel through solids and liquids (since they are longitudinal waves) whereas S-waves can only travel through solids (as they are transverse waves).
• This means the liquid part of the core blocks the passage of S-waves.