Question

Which one of the following statements about primary waves of earthquakes is not correct?
1. They are similar to sound waves.
2. They can travel only through solid materials.
3. They travel through gaseous, liquid and solid materials.
4. They move faster and are the first to arrive at the surface

Answer 1

Correct Answer - Option 2 : They can travel only through solid materials.

The correct answer is They can travel only through solid materials.

• Seismology is the study of earthquakes and seismic waves that move through and around the earth.
• Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.
• There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves.
  • Body waves traveling through the interior of the earth, body waves arrive before the surface waves emitted by an earthquake. These waves are of a higher frequency than surface waves.
    • The first kind of body wave is the P wave or primary wave.
      This is the fastest kind of seismic wave, and, consequently, the first to 'arrive' at a seismic station.
      The P wave can move through solid rock and fluids, like water or the liquid layers of the earth.
      It pushes and pulls the rock it moves through just like sound waves push and pull the air.
      P waves are also known as compressional waves, because of the pushing and pulling they do.
      Subjected to a P wave, particles move in the same direction that the wave is moving in, which is the direction that the energy is traveling in, and is sometimes called the 'direction of wave propagation.
    • The second type of body wave is the S wave or secondary wave, which is the second wave you feel in an earthquake.
      An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium.
      It is this property of S waves that led seismologists to conclude that the Earth's outer core is a liquid.
  • Surface waves traveling only through the crust, surface waves are of a lower frequency than body waves and are easily distinguished on a seismogram as a result.