1. EARTHQUAKES: WHY? AND HOW?

2. EARTHQUAKES sudden movement or shaking of the Earth
Caused by plate tectonic stresses releases stored Energy!
Located at plate boundaries
Resulting in breakage of the Earth’s brittle crust

3. Elastic Rebound Theory
Stresses build on both sides of a fault.
When stresses become too great, the rocks break and move.
This releases the built up energy and creates an earthquake.
Video Clip

4. 3 Types of Stress
Compression- occurs at convergent boundaries (plates move toward each other)
Tension- occurs at divergent boundaries (plates move away from each other)
Shear- occurs at transform boundaries (plates are sliding past each other)

5. PLATE TECTONIC STRESSES
Plate boundaries and faults (= cracks where plate sections are moving in different directions) cause friction as plates move
Plates in a fault zone have
STICK-SLIP motion
Periods of no movement (stick) and fast movement (slip)
Energy stored as plates stick
Energy released as plates slip

7. 3 Types of Faults
Normal Fault
Reverse Fault
Strike-Slip Fault

8. Normal Fault Result of plates moving apart.
The hanging wall moves downward in relation to the footwall.

9. Normal Fault: Tetons in Wyoming

10. Reverse Fault Result of plates moving together.
The hanging wall moves upward in relation to the footwall.

11. Reverse Fault: Sierra Madre

12. Strike-Slip Fault Result of plates sliding past each other.
The displacement is horizontal

13. Strike-Slip: San Andreas Fault

14. Parts of a Wave
Energy is transmitted in waves

15. EARTHQUAKE WAVES
FOCUS = place deep within the Earth and along the fault where rupture occurs
EPICENTER = geographic point on surface directly above focus
SEISMIC WAVES produced by the release of energy
move out in circles from the point of rupture (focus)
2 types of Seismic Waves:
surface & body (travel inside & through earth’s layers)

16. 2 Types of Body Waves Body waves travel faster than surface waves.
P waves: back and forth movement of rock; travel thru solid, liquid, gas
S waves: sideways movement of rock; travel thru solids only

17. 2 Types of Surface Waves
Travel along the ground, outward from an earthquake’s epicenter.
Slowest of the seismic waves
Do most of the damage
Two Types of Surface Waves:
Love Wave
Rayleigh Wave

18. Tsunami Deadly ocean waves most often caused by undersea earthquakes.
Tsunami Awareness
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