1. Earthquakes

2. Remember… Continental drift Plate tectonics
Which movement causes earthquakes?

3. Earthquakes Shaking and trembling of the earth’s crust.
About 8000 occur every day or one every 11 seconds
Caused by plates sliding beside each other (sliding/transform)
Tsunami - earthquake on the ocean floor: causing waves to become greater than 20 meters high

4. Faults
Faults are weaknesses in the rock and therefore earthquakes tend to happen over and over along the same faults.

5. Most major faults in the United States, particularly in California, are what are known as strike-slip faults.
A strike-slip fault is formed where two parts of the earth’s crust (plates) slide past each other.

6. Thrust Fault A thrust fault occurs when the plate moves in an
upward motion.

7. Normal Fault
Normal plate movement
is slipping in a downward
motion.

9. Seismic Waves
The three main types of seismic waves are: P waves, S waves, and L waves

10. Seismic Waves
…are waves of energy that travel through the Earth as a result of an earthquake

11. P Waves
Primary waves
Fastest waves
Arrive first at the epicenter

12. S Waves Secondary waves Move in up-down motion
(think of holding one end of a rope and shaking it up and down)

13. L Waves
Slowest moving seismic waves
Travel on top of Earth’s surface

14. Measuring Earthquakes
Seismograph-measures and detects seismic waves
Richter Scale- a scale that allows scientists to determine earthquake strength
1-10 levels at which an earthquake is measured. Above a 6 is very destructive

15. Measuring Earthquakes
Epicentre: the point on the Earth's surface that is directly above the centre of the earthquake
Most violent shaking happens at the epicenter

16. WHAT INFLUENCES THE AMOUNT OF DAMAGE AN EARTHQUAKE CAUSES?
- Magnitude of the earthquake (how it is)
- Distance of location from epicentre of the earthquake
- Type of movement of the plates or along fault
- Soil conditions (loose, solid, flexible, stiff)
- Construction type and quality of buildings