1. Earthquakes What is an earthquake? What can we learn from earthquakes?
How do we measure earthquakes?
Can we predict earthquakes?

2. What is an earthquake?
An earthquake is a vibration of the earth due to a rapid release of energy.
The energy travels out from the epicenter in waves.

4. What can we learn from earthquakes?
Origins of earthquakes were unknown until 1855 (faults)
Mechanisms of earthquakes were unknown until H.F. Reid conducted a study following the 1906 San Francisco earthquake.
Earthquakes happen after rock is bent and stretched to its limits due to tectonic plate movement.

5. Faults
Normal
Reverse
Strike-Slip

7. San Francisco Earthquake of 1906
8.3 on Richter Scale
7.8 on Moment Magnitude Scale
Major structural damage caused by earthquake
Total destruction caused by fires after earthquake

8. San Francisco 1906

9. San Francisco 1906

10. San Francisco 1906

11. San Francisco 1906

12. San Francisco 1906

13. Other Large Earthquakes
1556 China (deadliest)
1886 South Carolina (Eastern USA largest)
1960 Chile 9.6 Magnitude (largest)
1964 Alaska 9.2 Magnitude (N.A. largest)
2006 Hawaii 6.7 (most recent significant earthquake in U.S.)

14. Measuring Earthquakes
Seismographs use the property of inertia to measure the strength of earthquakes
The recorded pattern of an earthquake is called a seismogram
The seismograph records P waves first, then S waves, and finally Surface waves.
Three seismographs can triangulate the epicenter of an earthquake

16. Triangulate Epicenter
3 seismographs are used to pinpoint the epicenter which is directly above the focus of the earthquake

17. Body Waves Travel through the interior of the Earth

18. P Waves Primary waves move faster
Compression waves- the material travels parallel to the wave direction
Travel through solids, liquids, and gasses

20. S Waves Secondary waves move slower
Transverse wave- the material moves perpendicular to the wave direction
Travels through solids but not liquids or gasses

22. Surface Waves
Surface waves travel along the surface of the earth spreading out from the earthquakes epicenter
Love- Side to side
Rayleigh- elliptical motion similar to water waves

25. Measuring Earthquakes
Modified Mercalli Intensity Scale
Uses damage to determine strength I-XII
Richter Scale (ML)
measures according to amplitude of vibration
Moment Magnitude Scale (MW)
Measures displacement along a fault zone
Better for large earthquakes

26. Earthquakes
Most Earthquakes occur around the circum-Pacific belt. (Ring of Fire)
Liquefaction may add to damage of earthquakes

27. Liquefaction

28. Liquefaction

29. Triggered By Earthquakes
Tsunamis
Tsunami Flash
Warning System Flash
Landslides
Fire

32. Earth’s Layers Core Mantle Crust Iron Nickel Alloy
Solid Rocky Perdidotite
Crust
Thin rocky layer of mostly Basalt

33. Earth’s Layers Inner Core- solid metal alloy
Outer Core- molten metal alloy
Mesosphere- high pressure, gradual flow of solid rock
Asthenosphere- high temp, soft weak layer
Lithosphere- rigid structure, “floats” on upper asthenosphere

34. Predicting Earthquakes
Short Range (hours or days)
Efforts are made to monitor strain, uplifting, and subsidence in order to predict earthquakes.
Need more reliable means of prediction.
Long Range (years or hundreds of years)
Probability based on past events
Helps in engineering buildings

35. Earthquake Mitigation

36. Resources www.sciencecourseware.org