1. EARTHQUAKES 

2. EARTHQUAKES Earthquakes
 An earthquake is the vibration of Earth produced by the rapid release of energy
 Focus and Epicenter
• Focus is the point within Earth where the earthquake starts.
• Epicenter is the location on the surface directly above the focus.
 Faults
• Faults are fractures in Earth where movement has occurred.

3. Focus, Epicenter, and Fault

4. Slippage Along a Fault

5. EARTHQUAKES The Cause of an Earthquake  Elastic Rebound Hypothesis
• Most earthquakes are produced by the rapid release of elastic energy stored in rock that has been subjected to great forces.
• When the strength of the rock is exceeded, it suddenly breaks, causing the vibrations of an earthquake.

6. Elastic Rebound Hypothesis
Where a fault exists the two parts of the crust tries to move
This builds up elastic potential (stored) energy
Eventually the rocks break and a vibration begins at this breakage point (focus) and travels outward from there.
EARTHQUAKE
Now the process starts over!!!!!

7. Earthquake Waves Body Waves (P-Waves & S-Waves)  P-Waves (Primary)
• Travel in ALL directions from the focus.
Are waves that push (compress) and pull (expand) in the direction that the waves travel.
Travel through solids, liquids, and gases
Have the greatest velocity of all earthquake waves

8. Earthquake Waves Body Waves (P-Waves & S-Waves)  S-Waves (Secondary)
Travel in ALL directions from the focus
Shake particles at right angles to the direction that they travel
Slower velocity than P waves

9. Earthquake Waves Surface Waves  Surface Waves
Travel along the Earth’s Surface
Two main types
One type moves the Earth’s surface side to side.
The other type causes the surface of the Earth to roll like water waves.
Slower velocity than P-waves or S-waves
These waves cause the most destruction.

10. EARTHQUAKES Before & After an Earthquake  Foreshocks and Aftershocks
• A foreshock is a small earthquake that often precedes a major earthquake.
• An aftershock is a small earthquake that follows the main earthquake.