1. Earthquakes & Plate Tectonics
Earthquake: stored energy is suddenly released through a movement along a fault.
Fault: is a crack in the Earth’s crust, normally associated with, or form the boundaries between Earth’s tectonic plates.

2. Review Types of Faults…

3. How do we detect earthquakes?
Seismographs are machines that record seismic waves
Seismic waves: vibrations that travel through the Earth caused by earthquakes.

4. What are the types of Seismic Waves?
P waves
S waves
Surface waves

5. What are the types of Seismic Waves?
P waves: P stands for primary
These waves arrive first
Move with a push-pull motion

6. What are the types of Seismic Waves?
S waves: S stands for secondary
These waves arrive second
Move with a side-to-side motion

7. What are the types of Seismic Waves?
Surface waves – slowest
Cause the most damage
Move with an up and down and side-to-side motion

8. What are the types of Seismic Waves?

9. Epicenter versus Focus
Epicenter: a point on Earth’s surface that is directly above the focus of an earthquake.
Where shaking is strongest  most damage
Focus: point where the earthquake starts.
Where rock breaks along a fault and energy is released.

10. How do you locate an epicenter?
You need at least 3 seismic stations to locate an epicenter.
Where all three circles meet is the location of the epicenter.

11. How do you locate an epicenter?
P and S wave can help determine where the epicenter is located.
The farther you are the epicenter, the greater the S-P interval (time between when P wave hits and S wave hits)

12. How do we determine the size of an Earthquake?
Magnitude: Quantitative measurement of the size of an earthquake from its source.
The Richter scale is used to determine magnitude of an earthquake.

14. What is a Tsunami?
Tsunami: Destructive surge of water that is caused by an underwater earthquake.

15. Where do tsunamis occur?
80% occur within the Pacific Ocean’s “Ring of Fire”
Active area where volcanoes & earthquake are common