1. How and Where Earthquakes Happen
Chapter 12-1
How and Where Earthquakes Happen

2. Earthquakes Movement of ground caused by a release of energy
Movement along faults

3. Faults
Fault – break in rock

5. Why Earthquakes Happen
Faults locked
Stress caused faults to break

6. Elastic Rebound
Return of elasticity from deformed rock to original shape

8. Earthquake Parts Focus – point of 1st motion of a quake
Epicenter – point on surface above focus
Most damage

9. Focus 90% are shallow Shallow : 70km Intermediate : 70-300km
Deep: km

10. Seismic Waves Travel in all directions
Body wave – travel through the material
Surface wave – Travel on surface of material

11. Body Waves
P wave – Primary
Compression
Fastest
Solids, liquids, gases

12. Body Waves S wave – Secondary 2nd fastest Side to side motion
Only solids

13. Surface Waves Shallow faults Slowest Great damage Love – side to side
Rayleigh - rolling

14. Seismic Waves and the Interior
Useful in determining the Earth’s interior

15. Andrija Mohorovicic Moho - Seismic waves speed up around 30 km
Mantle is denser than crust

16. Shadow Zones
Area where no direct seismic waves can be detected

17. Convergent Ocean Environments

18. Divergent Oceanic Environments

19. Continental Environments

20. Fault Zones
Region of numerous faults

21. Earthquakes Away from Faults
New Madrid, Missouri
1811 and 1812
Felt in South Carolina
Ancient fault deep in Earth
Buried by sediment