How an earthquake spreads

The vibrations caused be an earthquake travel in the form of seismic waves. These waves spread away from the focus in all directions. As they move away from the focus, they grow weaker, which is why the ground further away from the focus shakes lesser.

There are two kinds of seismic waves, namely the body waves and the surface waves. Body waves are the fastest seismic waves and they move through the earth. Surface waves are slower and travel along the surface of the earth.

Body waves cause the most damage and cause the particles of rocks to move in different directions as they pass through the earth. There are two kinds of body waves. They are the compressional waves and the shear waves. Compressional waves push and pull rocks and cause buildings and other structures to contract and expand. These waves are also able to travel through all different kinds of matter. Shear waves make rocks bend or slide and buildings shake and are only able to travel through solids.

Surface waves are long, slow waves , producing slow rocking sensations and causing little or no damage. There are two kinds of surface waves, the Love waves and the Rayleigh waves. Love waves travel through the earth's surface horizontally at a speed of 4.4 kilometres per second, moving the ground from side to side. Rayleigh waves, the slowest of seismic waves, travel at a speed of about 3.7 kilometres per second, making the earth's surface roll.

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