How Do Shock Waves Produced by an Earthquake Travel?

Compressional Waves

• There are three types of seismic waves creating by earthquakes. The first wave is a compressional wave commonly referred to as a P-wave. A P-wave is the fastest moving seismic wave, traveling at 6.0 km/s. P-waves travel out in all directions from the focus of the earthquake moving back and forth in the same direction as the wave is traveling. For example, imagine that you are holding a Slinky with one end in each hand. If you were to create a P-wave with the Slinky, you would move your hands back and forth towards and away from each other, stretching and compressing the Slinky as you move. P-waves cause the molecules in the rocks to behave in the same fashion; the particles get compressed then rebound as the wave moves through the crust. P-waves can travel through solids, liquids, and gases.
  
  

Shear Waves

• Shear waves, also known as S-waves, move perpendicular to the direction of travel. They travel out in all directions from the focus of the earthquake. Imagine holding a Slinky. An S-wave would move through the crust as if you were moving the Slinky side to side. S-waves can only travel through solids. On average, they move at 3.5 km/s through the earth's crust.
  
  

Surface Waves

• Surface waves, also known as L-waves or Love waves, travel along the crust's surface. These waves move out from the epicenter (the point directly above the focus), as if ripples in a pond. They have alot in common with ocean waves, causing the molecules of the rocks to "roll" as they pass. Once again, imagine holding the Slinky. A surface wave would move across the surface as if you were using the Slinky as a jump rope. Surface waves move at different speeds, depending on the material they move through. The more dense the material, the faster the waves move. The average speed for a surface wave is 3.0 km/s. Surface waves cause the most damage during an earthquake. They also have the ability to cause liquefaction, the action of "liquefying" sediment as the wave passes. Buildings and foundations may sink during liquefaction, causing significant damage. Surface waves can travel through solids, liquids and gases. When a surface wave comes in contact with water, it has the ability to form a tsunami.