Body Waves 1

• Body waves have two types, P and S waves, and these waves carry information about what is happening beneath the Earth's crust during an earthquake. P waves are primary, or pressure waves, and they are the ones that travel the fastest. Longitudinal P waves move through rock and semi-liquid material, like magma. When it travels through the rock it moves it with a push and pull action, similar to the way sound waves move air around, for example, when a thunderclap makes the windows rattle. Humans can't hear P waves, they can only feel them, but according to the University of Utah, animals probably can both hear and feel them.
  
  

Body Waves 2

• S waves (shear waves) are slower than P waves and can only move through solid rock. The shape of S waves prevents them from moving through liquid. These waves move rocks up and down, or from side to side. Neither P nor S waves travel in straight lines, nor do they travel at constant speeds, and this allows scientists to find the epicenter of an earthquake. During an earthquake, people first feel the P waves followed minutes later by the S waves, which are the waves that cause most damage to buildings.
  
  

Surface Waves

• The movement of surface waves is restricted to the ground surface and might be compared to ripples of water on a lake. There are two types of surface waves. The first is called the Love wave, which moves in a similar way to an S wave except that it has no up and down action. The Love wave moves the ground from side to side on a horizontal plane and cause damage to building foundations. The second type of surface wave is the Rayleigh wave. These waves are similar to rolling, sea waves and they move vertically and horizontally on a vertical plane.
  
  

Seismographs

• A seismograph records an earthquake's energy during the event. The seismograph machine consists of a base and a mass, and during an earthquake the base moves while the mass remains still. The base motion creates an electrical voltage, which then records the earthquake movement in waves. This recording is interpreted by using the Richter scale, which measures the amplitude of the waves drawn on the seismograph. Satellite technology also plays a part in detecting earthquakes as satellite images show hot spots in earthquake areas before the event. (