1. Aim: What is an earthquake?
Do now: In your notes, explain where most earthquakes occur and Why?
Japan

2. Earthquakes
- are vibrations in the crust caused by moving crustal plates.
California

3. Focus - the origin (starting point) of the earthquake underground.
B. Epicenter – the location on the surface directly above the focus.

4. II. Causes of Earthquakes
the release of potential energy stored in rock.
energy is released in all directions

5. A. Elastic Rebound Hypothesis
- Deformation of rocks (stressing/bending) cause them to build up pressure (energy).
- When they break, the stored energy is released which results in the vibrations.

6. III. Measuring Earthquakes
Seismology – the study of earthquake waves (energy).
Seismographs –
instruments that
record earthquake
waves (energy).
*Seismos = earthquake

7. Seismogram – a graph produced by recording the ground motion on a seismograph.

8. Creation of Seismogram

9. Richter Scale: Measures the magnitude (strength) of an earthquake from the seismogram.

10. IV. Types of Seismic Waves (earthquake waves)
epicenter
created at the start of the earthquake.
What do you notice about the waves in the diagram?
wave motion through Earth helps scientists theorize about the inside of Earth and it’s layers.

11. How would you describe the motion of this wave?
A. Body Waves
Travel through the Earth’s interior.
1. P-waves (Primary/Compression Waves)
push-pull waves that compress and expand
the ground in the direction that the waves travel.
How would you describe the motion of this wave?

12. 2. S-Waves (Secondary/Transverse Waves)
move the ground at right angles (up and down)to the direction that they travel.
How would you describe the motion of this wave?

13. P- Wave S-Wave P & S Wave Animation What can this wave travel through?
Travels through
solids and liquids
Travel Faster
Arrives First
Travels through solids, Cannot go through
Liquids
Travel Slower
Arrives Second
How would you describe the speed of this wave?
When does this wave arrive compared to the other?

14. - Most destructive since they are on the surface
B. Surface Waves –seismic waves that travel along the Earth’s outer layers (crust).
- Follow P and S waves
- Most destructive since they are on the surface
China

15. C. Aftershocks and Foreshocks
movements of the crust that follow a major earthquake called aftershocks.
small vibrations called foreshocks come before a major earthquake.
Anchorage, Alaska

16. III. Earthquake Zones
The “Ring of Fire” is the area that surrounds the Pacific Plate which is marked with volcanoes and earthquakes.

17. Closure 1: Why could someone think that most
earthquakes cause little damage and little
loss of life?
Because most occur in
areas that are not
populated by people or
cities.
Tokyo, Japan

18. Closure 2:
Review Book: p #1-10