1. Types of Stress that cause Earthquakes
Chapter 8

2. What is an Earthquake?
An Earthquake is the vibrations produced when a rock snaps and breaks under different types of stress.

3. Types of Stress Tensional – pulls rocks APART
Compressional – pushes rocks TOGETHER
Shearing – pulls rocks ALONG each other

4. The Elastic Rebound Theory
Rocks will bend until they reach their Elastic Limit.
Then they will break (crack)
This forms a Fault

5. How do Earthquakes Occur?
Rocks on a fault are jagged & get stuck when plates move.
Stress Builds
Rocks bend until they can’t & then snap back to their original position. (Elastic Rebound Theory)

6. Parts of a Fault
Footwall
Hanging Wall

7. Normal Fault

8. Caused by Tensional Stress
Rocks/plates are pulled apart
Tension causes the hanging wall to fall down.
Divergent Boundary

9. Normal Fault

10. Normal Fault

11. Normal Fault

12. Reverse Fault

13. Caused by Compressional Stress
Rocks/plates are pushed together.
Causes the Hanging wall to move up.
Earthquakes!!!!
Convergent Boundary

14. Reverse Fault

15. Reverse Fault

16. Thrust Fault
A special Reverse fault
Angle of fault plane is shallow.

17. Strike-Slip Fault

18. Caused by Shearing Stress
Rock/plates are sliding in opposite directions.
Movement is only horizontal.
EARTHQUAKES!!!
Transform Boundary

19. Strike Slip Fault

20. Strike – Slip Fault

21. Oblique-Slip Fault Horizontal and Vertical Movement
Caused by Tensional and Shear Stress.
Transform and Divergent Boundaries