1. 8.1 What Is an Earthquake?
 Earthquake - vibration of Earth produced by rapid release of energy - Caused by motion of tectonic (lithospheric) plates.
 Focus - point within Earth where quake starts.
 Epicenter - location on surface directly above the focus.
 Faults - fractures in Earth where
movement has occurred.

2. Focus, Epicenter, and Fault

3. 8.1 What Is an Earthquake? Causes of Earthquakes
 Elastic Rebound Hypothesis
• When plates move, rocks along edge experience immense pressure
• When the strength of the rock is exceeded, it suddenly breaks, causing the vibrations of an earthquake.

4. Elastic Rebound Hypothesis
Animation Japan 2011

5. 8.1 What Is an Earthquake?  Aftershock - small quake that follows
main quake.
 Foreshock - small quake that often
precedes a major earthquake.

6. Types of Boundaries  Divergent Plate Boundary - plates move apart (A)
 Convergent Plate Boundary - oceanic plates dive beneath continental or oceanic plates (subduction) (B)
 Transform Fault Boundary –
plates move horizontally past
one another (C)

7. Slippage Along a Fault

8. A transform fault boundary occurs where two plates
move toward each other.
move away from each other.
move past each other.
move over each other.
Example: San Andreas Fault