1. Earthquakes!!

2. Focus and Epicenter Focus – where the earthquake happens
Epicenter – the spot on the surface above the focus

3. Elastic Rebound
Stress causes the ground begins to be deformed. An earthquake occurs when a rock passes its point of maximum elasticity. After it breaks, it regains its original shape (but not position.)

4. Seismograph and inertia
Notice that it is the mass that is moving, not the drum. A heavy mass is used (more inertia) and is suspended so that it is less effected by whatever it is attached to. See the animation next.

5. Seismographs
To view this animation, click "View" and then "Slide Show" on the top navigation bar.

6. Seismic Waves P(Primary) – body wave S(Secondary) – body wave
L(Long) – surface wave

7. Earthquake Waves
To view this animation, click "View" and then "Slide Show" on the top navigation bar.

8. Seismogram- recording from seismograph
P wave arrives first
S wave then arrives
The time between them tells you how far away they came from. Notice that it is 5 minutes from P to S wave.
The graph on the next page shows how to do this
5 minutes

9. Richter Scale

10. Tsunami

11. Tsunami travel times to Hawaii

12. Old Tsunami Photo

13. One of the greatest disasters
Safety tip. If you see the ocean floor, and the ocean has retreated, head for high ground as fast as possible.