# [Solved] what are seismic waves

What are seismic waves? Seismic waves are the waves of energy caused by breaking of rock within the earth or an explosion. These waves are the energy that travels through the earth and is recorded on seismographs. There are many different types of these waves, but the two main ones are the body waves that usually travel though in inner layer of the earth, and the surface waves that only move around the surface of the planet. Body waves travel through the inner layer of the earth, and they usually divide into two types the P waves and the S wave. P waves is the first type of body waves.

They also called the primary waves. These are the fastest of seismic wave, and they 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. Have you ever heard a big clap of thunder and heard the windows rattle at the same time? The windows rattle because the sound waves were pushing and pulling on the window glass much like P waves push and pull on rock. Sometimes animals can hear the P waves of an earthquake.

Dogs, for instance, commonly begin barking hysterically just before an earthquake hits. Usually people can only feel the bump and rattle of these waves. 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 [1]. On the other hand, the S waves is the second type of the body waves. They are also called the secondary waves.

People usually feel these waves in an earthquake. S wave is slower than a P wave and can only move through solid rock, not through any liquid medium. S waves are what led seismologists to conclude that the Earth’s outer core is a liquid. S waves move rock particles up and down, or side-to-side–perpendicular to the direction that the wave is traveling in the direction of wave propagation [1]. Surface waves usually travel along the earth’s surface. They travel slower than body waves. Because of their low frequency, long duration, and large amplitude, they can be the most destructive type of seismic wave.

There are two types of surface waves: Rayleigh waves and Love waves [2]. The first kind of surface wave is called a Love wave, named after A. E. H. Love, a British mathematician who worked out the mathematical model for this kind of wave in 1911. It’s the fastest surface wave and moves the ground from side-to-side. Confined to the surface of the crust, Love waves produce entirely horizontal motion [1]. The other kind of surface wave is the Rayleigh wave, named for John William Strutt, Lord Rayleigh, who mathematically predicted the existence of this kind of wave in 1885.

A Rayleigh wave rolls along the ground just like a wave rolls across a lake or an ocean. Because it rolls, it moves the ground up and down, and side-to-side in the same direction that the wave is moving. Most of the shaking felt from an earthquake is due to the Rayleigh wave, which can be much larger than the other wave [1]. As a conclusion, seismic waves are waves of energy that travel through earth. They travel into the inner layer of earth through the body waves, and travel along the earth’s surface through the surface waves.

Work Sited
[1]. http://www.geo.mtu.edu/UPSeis/waves.html
[2]. http://en.wikipedia.org/wiki/Seismic_wave