What are earthquakes? What is the extent of damage caused by them?

1. Earthquakes

2. https://www.youtube.com/watch?v=zKgdzakU
Q7Q
https://www.youtube.com/watch?v=xjDgJh
S4

3. What are they?
• A vibration in the earth’s crust caused by the
sudden release of stored energy in the rocks
found along fault lines
• Occurs when there is plate movement along
plate boundaries

4. Where do they occur?
• They can occur on
convergent/divergent/transform plate
boundaries
• Occur most on convergent plate
boundaries because the stress builds up
when a plate subducts beneath another

5. How do they form?
• Jagged sides of the plates cause the plates to be
stuck when they try to slide past each other.
• The friction of movement builds up stress in the
rocks. When they continue to move, more stress
builds up.
• When they can no longer withstand the increasing
stress, they can slip many metres,
• releasing massive amounts of stored energy in the
form of seismic waves, which is an earthquake

6. Epicenter: The point on
the earth’s surface
directly above the focus
Focus: The point of
sudden energy release

7. Types of earthquakes
Type of
earthquake
Deep-focus earthquake Shallow-focus earthquake
Location of
focus
• Occurs between 70-700km
below earth’s surface
• Occurs in the upper 70km of
earth’s crust
Impact on land • Smaller impact on land as
vibrations/seismic waves take
a longer time to reach the
surface and would have lost
most energy by then
• Greater impact on land as the
vibrations/seismic waves reach
the land surface more quickly

8. Extent of earthquakes
• Population density
• Level of preparedness
• Distance from the epicentre
• Time of occurrence
• Type of soil

9. https://www.youtube.com/watch?v=1J8Feyr38Ss

10. http://www.youtube.com/watch?v=xy
KgamjegtQ
http://www.youtube.com/watch?v
=Wx9vPv-T51I

11. Banda Aceh, Sumatra, Indonesia

12. Sri Lanka

13. Sri Lanka

14. Sri Lanka

15. Khao Lak, Thailand

16. http://abcnews.go.com/Archives/video/jan-17-1995-earthquake-japan-9421417
http://www.youtube.com/watch?v=3p7xt_U34pM

17. What affects the
extent of
earthquakes?
Psst.. Points are found on pages 31-32.

20. Why do people continue to live
in area prone to earthquakes?
• Fatalistic approach
• Acceptance approach
• Adaptation approach

21. Indonesia

22. Japan
http://www.youtube.com/watch?v=VKtGabaesXw

23. San Francisco
http://www.youtube.com/watch?v=dJBS94GVyuo