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With reference to secondary seismic waves (S waves) which of the following statements are correct? I. These are also called longitudinal waves. II. These waves cannot pass through liquids. III. Their speed is less than surface waves.

With reference to secondary seismic waves (S waves) which of the following statements are correct? I. These are also called longitudinal waves. II. These waves cannot pass through liquids. III. Their speed is less than surface waves. Correct Answer Only II

Seismic waves are waves of energy that travel through the Earth’s layers. These waves are a result of earthquakes, volcanic eruptions, magma movement, large landslides, and large human-made explosions. Seismic waves are an important source of knowledge about the structure of the Earth’s interior. Seismic waves are of two types - Body waves and surface waves.
Key Points

Body waves are generated due to the release of energy at the focus and move in all directions traveling through the interior of the earth. There are two types of body waves (a) P-waves or primary waves (b)  S-waves or secondary waves 

 P-waves or primary waves:

  • Primary waves are called so because they are the fastest among the seismic waves and are recorded first on the seismograph.
  • P-waves are also called Longitudinal waves because the displacement of the medium is in the same direction.
  • These waves are of relatively high frequency and are the least destructive among the earthquake waves.
  • They can travel in all mediums.

 S-waves or secondary waves:

  • Secondary waves or S-waves are recorded second on the seismograph. They are also called transverse waves or shear waves.
  • Transverse waves or shear waves mean that the direction of vibrations of the particles in the medium is perpendicular to the direction of propagation of the wave. Hence, they create troughs and crests in the material through which they pass (they distort the medium).
  • S-waves arrive at the surface after the P-waves.
  • These waves are of high frequency and possess higher destructive power compared to P-waves.
  • The trembling on the earth’s surface caused due to these waves is from side to side (horizontal).
  • S-waves cannot pass through fluids (liquids and gases).
  • They travel at varying velocities through the solid part of the Earth.

Important Points

  • The body waves interact with the surface rocks and generate a new set of waves called Surface waves (L-waves). These waves move only along the surface.
  • They are low–frequency transverse waves..
  • They are the slowest among the earthquake waves and are recorded last on the seismograph.

Hence Only Statement II is correct with reference to Secondary seismic waves (S waves).

Related Questions

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