When an earthquake occurs, the shockwaves of released energy that shake the Earth and temporarily turn soft deposits, such as clay, into jelly (liquefaction) are called seismic waves, from the Greek ‘seismos’ meaning ‘earthquake’.
S-waves, also known as secondary waves, shear waves or shaking waves, are transverse waves that travel slower than P-waves.
Rayleigh waves, also called ground roll, travel as ripples similar to those on the surface of water.
The epicenter of an earthquake sends out waves which are like an object dropped on to a still body of water that sends out ripples. Seismic waves can be classified into two basic types: body waves which travel through the Earth and surface waves, which travel along the Earth's surface.
Body waves are of two types: compressional or primary (P) waves and shear or secondary (S) waves. Love waves have a particle motion, which, like the S-wave, is transverse to the direction of propagation but with no vertical motion.
Particle motion for Rayleigh and Love waves are different: Rayleigh waves have retrograde particle motion confined to the vertical plane of motion, whereas Love waves have purely transverse motion in the horizontal plane. Earthquakes radiate seismic energy as both body and surface waves but deep earthquakes generally do not generate surface waves.


Seismic waves are usually generated by movements of the Earth’s tectonic plates but may also be caused by explosions, volcanoes and landslides.Seismologists use seismographs to record the amount of time it takes seismic waves to travel through different layers of the Earth. P-waves and S-waves are sometimes collectively called body waves.P-wavesP-waves, also known as primary waves or pressure waves, travel at the greatest velocity through the Earth.
People have claimed to have observed Rayleigh waves during an earthquake in open spaces, such as parking lots where the cars move up and down with the waves. Those waves that are the most destructive are the surface waves which generally have the strongest vibration. P- and S- waves are called "body waves" because they can travel through the interior of a body such as the Earth's inner layers, from the focus of an earthquake to distant points on the surface.
The P wave, or compressional wave, ultimately compresses and expands material in the same direction it is travelling. They arrive after the main P and S waves and are confined to the outer layers of the Earth. Their side-to-side motion (like a snake wriggling) causes the ground to twist from side to side, that’s why Love waves cause the most damage to structures. As the waves travel through different densities and stiffness, the waves can be refracted and reflected.


When they travel through air, they take the form of sound waves – they travel at the speed of sound (330 ms-1) through air but may travel at 5000 ms-1 in granite.
An earthquake releases energy as shock waves, the so-called seismic waves, which ripple across the earth's surface. Rayleigh waves create a rolling, up and down motion with an elliptical and retrograde particle motion confined to the vertical plane in the direction of propagation. They are typically generated when the source of the earthquake is close to the Earth’s surface. Although surface waves travel more slowly than S-waves, they can be much larger in amplitude and can be the most destructive type of seismic wave. P-waves shake the ground in the direction they are propagating, while S-waves shake perpendicularly or transverse to the direction of propagation (i.e.



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