1. Earthquake Waves

2. “Seismic” always has to do with earthquake activity
Seismic Waves
As the rock layers are shaking back and forth they send out waves of vibration called Seismic Waves
“Seismic” always has to do with earthquake activity

3. Epicenter
Fault
Focus
Seismic Waves

4. Seismic Waves are waves of vibration sent out in all directions from the FOCUS (point of the discharge of energy from rock fracture)

5. Focus The point below the surface where the rock layers break and move
Epicenter The point on the surface, directly above the focus. Where the greatest damage usually occurs

6. Types of Seismic Waves

7. Body Waves are waves that travel through the body of the earth
Surface waves only travel along the surface of earth

8. 2 types: P waves and S waves
Body Waves
2 types: P waves and S waves

9. Primary Waves AKA P-Wave
Type of Longitudinal Wave
Causes back and forth motion
Follows the same direction as the energy transfer

10. P-Waves
Type of COMPRESSIONAL wave- means they move through (compress) a solid or liquid by pushing or pulling similar to the way sound travels through the air
Will travel through solid, liquid or gas
Travels at:
7.8 – 8.5 kps in mantle
7.2 kps in oceanic crust
3.5 kps in continental crust

11. The particles of the material a P Wave pushes through move in the direction of the P wave's energy. This is called the direction of wave propagation.

12. Primary or “P” Wave

13. Secondary Wave-AKA S-Wave
The 2nd wave to Move out from the earthquake focus
Move slower than primary waves
Movement: Move at right angles to primary waves causing rocks to move up and down and side to side … this is known as a (transverse wave)
A type of seismic wave that moves the ground up and down or side to side

14. Secondary Wave AKA S-Wave
Particle motion is perpendicular to direction of energy transfer
Transverse or Shear Wave
Will travel only through solids (solid rock)
Travels 4 – 5 kps

15. Secondary Wave

16. Secondary or “S” Wave

17. Comparing Seismic Waves

18. Surface Waves

19. Two main types of surface waves:
Love Wave
Rayleigh Wave

20. Love Wave

21. Love Waves Love Waves travel less than 4 kps
Move side-to-side; like a snake
Cause the most damage

22. Seismic Waves

24. Seismogram with the P-Wave, S-Wave and L-Wave

25. Seismic Risk in the US

26. Triangulation