Earthquake Waves

What do we feel in an earthquakes?

• Waves produced by an earthquake are called seismic waves.
• Seismic waves radiate in all directions from the focus.
• This is the point below the surface where the waves (and the earthquake) originate.
• The point on the Earth's surface above the focus is called the epicenter.
• We will look at three types of seismic waves: Primary, Secondary and Surface waves.

Primary (P) waves

• P-waves are longitudinal waves.
• P-waves create moving compression and rarefaction in rock.
• P-waves travel thousands of kilometers per hour.
• P-waves pass through solids, liquids and gases.
• P-waves will travel through the Earth.

Secondary (S) waves

• S waves (or shear waves) are transverse waves.
• The rock moves at right angles to the direction of motion.
• S-waves travel slower than P waves.
• S-waves cannot pass through liquids.
• S-waves will also travel through the Earth.

Surface waves

• Surface waves are produced when P and S waves hit the Earth's surface.
• Surface waves cause a rolling motion on the surface.
• Surface waves travel slower than S waves
• Surface waves take longer to reach any point because they propagate (move) along the surface.
• Surface waves cause the most damage.