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

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

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

4. 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)

5. Parts of a Fault
Footwall
Hanging Wall

6. Normal Fault

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

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

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

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

11. Oblique-Slip Fault Horizontal and Vertical Movement
Caused by Tensional and Shear Stress.