type of seismic wave

Body waves

A body wave is a seismic wave that moves through the interior of the earth,

as opposed to surface waves that travel near the earth's surface.

P and S waves are body waves.

Each type of wave shakes the ground in different ways

compressional waves

shear waves

Compressional Waves

• The first type of body wave is called the primary wave or pressure wave, and is commonly referred to as P-waves.
• This type of seismic body wave travels at the greatest velocity through the ground.
• As a longitudinal compressional waveform, P-waves move in the same way as sound waves.
• As they spread out, they alternately push (compress) and pull (expand) the ground as they move through it.
• P-waves are able to travel through both solid rock and liquid material, such as volcanic magma or oceans.
• They travel at velocities ranging from "1,600–8,000 m/s", depending on the material they’re moving through.
• Because of their speed, they are the first type of wave to be felt and to register on a seismograph during an earthquake

shear waves

• a wave in which the propagated disturbance is a shear strain in an elastic medium.
• S-Waves. Secondary , or S waves, travel slower than P waves and are also called "shear" waves because they don't change the volume of the material through which they propagate, they shear it. ... As a transverse wave passes the ground perpendicular to the direction that the wave is propagating. S-waves are transverse waves ...
• Secondary waves (also called shear waves, or S waves) are another type of body wave.
• They move a little more slowly than P waves, and can only pass through solids. As S waves move, they displace rock particles outward, pushing them perpendicular to the path of the waves.
• "S waves"are slower than "P waves" and they can only travel through solid rock.
• "S waves" move the particles it pushes through up and down or side to side (perpendicular to the motion of the S waves energy).

surface waves

Characteristics of surface waves :-

1-large amplitude,

2-long wavelength,

3-wide range of frequencies (large bandwidth),

4-travel slowly

Rayleigh waves

Love waves

Rayleigh wave

• Rayleigh Wave. Rayleigh waves are formed when the particle motion is a combination of both longitudinal and transverse vibration giving rise to an elliptical retrograde motion in the vertical plane along the direction of travel
• Rayleigh waves are a type of surface acoustic wave that travel along the surface of solids. They can be produced in materials in many ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects.
• Rayleigh Waves—surface waves that move in an elliptical motion, producing both a vertical and horizontal component of motion in the direction of wave propagation. Particle motion consists of elliptical motions (generally retrograde elliptical) in the vertical plane and parallel to the direction of propagation.

love waves

• In elastodynamics, Love waves, named after Augustus Edward Hough Love, are horizontally polarized surface waves.
• The Love wave is a result of the interference of many shear waves (S-waves) guided by an elastic layer, which is welded to an elastic half space on one side while bordering a vacuum on the other side.
• In seismology, Love waves (also known as Q waves (Quer: German for lateral)) are surfaceseismic waves that cause horizontal shifting of the Earth during an earthquake.
• Augustus Edward Hough Love predicted the existence of Love waves mathematically in 1911.
• These waves are observed only when there is a low velocity layer overlying a high velocity layer/ sub–layers
• The particle motion of a Love wave forms a horizontal line perpendicular to the direction of propagation (i.e. are transverse waves).
• The amplitude, or maximum particle motion, often decreases rapidly with depth.
• Since Love waves travel on the Earth's surface, the strength (or amplitude) of the waves decrease exponentially with the depth of an earthquake.
• However, given their confinement to the surface, their amplitude decays only as 1/√r, where r represents the distance the wave has travelled from the earthquake.

• Large earthquakes may generate Love waves that travel around the Earth several times before dissipating.
• Since they decay so slowly, Love waves are the most destructive outside the immediate area of the focus or epicentre of an earthquake.
• They are what most people feel directly during an earthquake.
• In the past, it was often thought that animals like cats and dogs could predict an earthquake before it happened.
• However, they are simply more sensitive to ground vibrations than humans and able to detect the subtler body waves that precede Love waves, like the P-waves and the S-waves.

Love waves Motion :-

• Love Waves-surface waves that move parallel to the Earth’ surface and perpendicular to the direction of wave propagation.
• Particle motion consists of alternating transverse motions.
• To aid in seeing that the particle motion is purely horizontal, focus on the Y axis (red line) as the wave propagates through it.
• Amplitude decreases with depth.
• Material returns to its original shape after wave passes.