What do we feel in 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 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.