1. Chapter 8 Earthquakes

2. Section 1: What are Earthquakes?

3. Earthquakes
Mainly occur along faults near the edges of tectonic plates.
Elastic rebound is the direct cause of earthquakes- return to original shape

4. EQs differ depending on what type of plate motion causes them.
Seismic waves are classified as body waves or surface waves.

5. Body waves travel through the Earth’s interior, while surface waves travel along the surface.
2 types of body waves:
P waves
S waves

6. Seismic Waves 2 types of body waves:
P waves: fastest waves that travel thru solid, liquid, and gases
Called Primary
Waves

7. S waves: second fastest waves, cannot travel thru parts of the Earth that are completely liquid
Secondary waves

8. Seismic Waves Surface Waves: travel on surface of Earth
Do most damage to buildings and structures

9. Deformation: change in shape of rock due to stress
2 types:
Plastic deformation: bends like a piece of molded clay; does not lead to earthquakes
Elastic deformation: breaks like a stick; does lead to earthquakes

10. All Earthquakes are NOT the Same
Plate Motion
Major Fault Type
EQ Characteristics
Transform
Strike-slip fault
Moderate, shallow
Convergent
Reverse Fault
Strong, deep
Divergent
Normal Fault
Weak, shallow

11. Section 2: Earthquake Measurement

12. Earthquake Measurement
Seismographs can tell when and where an earthquake took place.
Epicenter is the point on Earth’s surface directly above where an EQ started.
Focus is inside the Earth where the EQ began.

13. The S-P time method is the simplest to use to find an earthquakes epicenter.
Seismologists use the Richter scale to measure an earthquake’s strength.

14. Seismologists use the Modified Mercalli Intensity Scale to measure an earthquakes intensity.

15. Section 3: Earthquakes and Society

16. Earthquake Hazards
Earthquake hazard measures how prone/likely an area is to experiencing EQ in the future.
Some EQ predictions are based on the relationship b/w EQ strength and EQ frequency. As frequency decreases, strength increases.

17. EQ usually collapse a structure by displacing the structure's center of gravity.