Earthquake Waves

Earthquake Waves

PRIMARY WAVES/P-WAVES
  • P-waves moves longitudinally i.e. the propagation and vibration are in a same direction similar to the sound waves. They are the fastest of all the earthquake waves. They travel through gaseous, liquid and solid materials.
 
SECONDARY WAVES/S-WAVES
  • S-waves are second to reach at the surface after P-waves. As they can travel only through solid materials of the Earth, they cannot pass through Earth’s outer core, therefore their shadow zone is broader than that of P-waves. This reveals that the outer core of the Earth is not in solid form.
  • S-waves propagate transversally i.e. the direction of propagation and the direction of vibration is perpendicular to each other.
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SURFACE WAVES
  • Surface waves are generated when the body waves interact with the surface rocks. As they move along the surface and the direction of the vibration is perpendicular to the propagation, these waves are considered as the most damaging one.

Earthquake Waves
 
THE EMERGENCE OF SHADOW ZONE
  • Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the ‘shadow zone’.
  • Seismographs located at any distance within 105° from the epicenter, recorded the arrival of both P and S-waves.
  • Seismographs located beyond 145° from the epi-centre record the arrival of P-waves, but not that of S-waves.
  • Thus, a zone between 105° and 145° from epicenter was identified as the shadow zone for both the types of waves.
 
 

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