Waves can be used to probe the structure of the Earth. Any large mechanical disturbance such as an earthquake or nuclear explosion acts as a source of seismic waves, another term for waves that propagate through the Earth. There are three main types of seismic waves. One is called an S wave (S for Shear). Like shear waves in a metal bar, S waves are transverse in nature with the displacement of the solid Earth perpendicular to the direction of propagation. Another type of seismic wave is called a P wave (P for pressure). P waves are longitudinal sound waves. Although S and P waves have different velocities, they both propagate in to the body of the Earth. A third type of wave travels on the surface. These surface waves travel more slowly than S and P waves and are similar to water waves on the surface of a lake.
DefinitionBack to Top
The S waves are the major type of seismic waves that are sent through the Earth. A S wave is sometimes referred to as a "standing wave" because the wave moves perpendicular to the direction of the wave motion. The S waves can only be generated and passed through solid material because this type of seismic waves is related to the closeness or compactness of molecules.
CharacteristicsBack to Top
Some of the characteristics of S waves are listed below:
- S waves travels with high frequency
- These waves are transverse in nature,that is perpendicular to the direction of propagation.
- S waves spreads all directions from the focus
- It travels with a varying velocities through the solid parts of the Earth crust, mantle are core.
S wave or secondary waves are one of the important waves among the seismic waves. Since S waves arrive after the P waves it is termed as secondary waves. The S waves being slower are received after the P waves by an observational instrument that has detected the waves. In S waves the particles vibrate back and forth at right angles to the direction in which the wave is moving.→ Read More
P Waves and S WavesBack to Top
The P and S waves are generated some distance beneath the surface at the focus of an earthquake from which they radiate in all directions. P and S waves are generated simultaneously during the earthquake. P wave is a longitudinal wave whereas S wave is a transverse wave. P waves can travel through earth almost twice as fast as S waves, so P waves detected faster in seismograph, an instrument that senses and records earthquakes. Liquids are unable to transmit the side-to-side S waves but do propagate compressional P waves.