Types of Earthquake Waves

What are Earthquake Waves?

A seismic wave is that which is propagated by some kind of elastic deformation, or, a change in shape that disappears when the forces are removed.

Body Waves

A seismic wave that can travel through the interior of the earth is a Body wave.
P-waves and S-waves are body waves.

Primary Waves

Primary Waves
Primary Waves

P waves are compression waves because the rocky material in their path moves back and forth in the same direction as the wave travels alternately compressing and expanding the rock. P waves are the fastest seismic waves; they travel in strong rock at about 6 to 7 km per second.

Secondary Waves

Secondary Waves
Secondary Waves

S waves, which shear, or twist, rather than compress the rock they travel through. S waves travel at about 3.5 km per second. S waves cause rocky material to move either side to side or up and down perpendicular to the direction the waves are traveling, thus shearing the rocks.

Both P and S waves help seismologists to locate the focus and epicenter of an earthquake.

Surface Waves

Earthquakes contain surface waves that travel out from the epicenter along the surface of the Earth. Two types of these surface waves occur: Rayleigh waves, named after British physicist Lord Rayleigh, and Love waves, named after British geophysicist A. E. H. Love. Surface waves also cause damage to structures, as they shake the ground underneath the foundations of buildings and other structures.

Rayleigh Waves

On the surface of the Earth, Rayleigh waves cause rock particles to move forward, up, backward, and down in a path that contains the direction of the wave travel. This circular movement is somewhat like a piece of seaweed caught in an ocean wave, rolling in a circular path onto a beach.

Love Waves

Love wave causes rock to move horizontally, or side to side at right angles to the direction of the traveling wave, with no vertical displacements.

Rayleigh and Love waves always travel slower than P waves and usually travel slower than S waves.

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