2. Warm Up
A stretched spring attached to two fixed points is compressed on one end and released.
The resulting wave travels back and forth between the two fixed ends of the spring until it comes to a stop. This mechanical wave is an example of a
A transverse wave B longitudinal wave. C superpositioned wave D refracted wave. B

3. Earthquakes Key Terminology Seismic waves Body waves
Surface waves P waves
S waves Surface waves
Seismograph Seismogram
Focus Epicenter
Time-travel curve Magnitude
Intensity Richter Scale
Mercalli Scale Logarithmic
Liquefaction Fault scarp
Tsunami Hazard potential map
Elastic Rebound

4. Earthquakes
Global Earthquake Locations

5. Earthquakes
Dr. R. B. Schultz

6. Earthquake Hazard Potential Map
Parkfield, CA
“Earthquake Capital of the World”

7. One of the Largest Earthquakes Ever Recorded: 1964 Anchorage, AK - Registered 8.6 on Richter Scale

8. Do earthquakes in Alaska pose any threat to California?

9. Earthquake Destruction in California Northridge, 1994

10. Earthquake Destruction in California San Francisco, 198910

11. Earthquake Destruction in California San Francisco, 198911

12. Earthquakes What is an earthquake and what causes it?
Earthquake: the sudden release of energy in the Earth's crust that creates seismic waves.
Earthquakes are caused mostly by rupture of geological faults, but also by volcanic activity, landslides, mine blasts, and nuclear experiments.
If the stress of plate motion exceeds the ability of rocks to bend, they break.
The resultant fracture line is called a fault.
When the rocks break, energy is transmitted through the ground in waves.
The longer that the energy is stored up, the more likely that a strong earthquake will occur.

13. Earthquakes The Two (2) Types of seismic waves
Body waves -- travel through interior
Surface waves -- travel on surface of earth
Specific Body Waves
Primary or "P" Waves: Highest velocity
Secondary or "S" Waves: Slower than P waves but faster than surface waves. Cannot travel through liquids
Surface Waves
Cause vertical & horizontal shaking
Travel exclusively along surface of earth
Often are the most destructive types of waves

14. Primary or “P” Wave
(look at the way the particles are moving relative to the wave)
Secondary or “S” Wave

15. Primary or “P” Wave
What kind of wave is this?
Longitudinal
Secondary or “S” Wave
Transverse

18. Seismograph
An Instrument that is used to measure the magnitude of an Earthquake.

20. Seismogram Printout

21. Seismogram Printout

22. Focus and Epicenter of Earthquake
An earthquake's point of initial rupture is called its focus.
The epicenter is the point on the Earth's surface that is directly above the focus.

23. Focus and Epicenter of Earthquake23

25. What is the magnitude of an earthquake?
Magnitude: measure of energy released during earthquake.
Most common magnitude measure is Richter Magnitude, named for the renowned seismologist, Charles Richter.
Logarithmic scale. Increasing one whole unit on Richter Scale represents 10 times greater earthquake
How is it measured?
One measures the amplitude of largest S wave on seismograph record.

26. What is the Intensity of an Earthquake?
Intensity refers to the amount of damage done in an earthquake
Mercalli Scale is used to express damage
Much less quantitative than Richter Scale

28. Is Earthquake Prediction Possible?
How can scientists predict an earthquake?
Currently, that is not possible.

29. What are the hazards associated with quakes?
Shaking, Especially of structures such as buildings which have their own natural period.

30. What are the hazards associated with quakes?
Shaking, Especially of structures such as buildings which have their own natural period.

31. What are the hazards associated with quakes?
Liquefaction: failure of supporting soil during an earthquake

32. What are the hazards associated with quakes? Ground displacement:
Fault scarps produced: the displacement of the land surface by movement along faults. 32

33. Tsunamis (NOT tidal waves):
Tsunamis are huge waves that can be generated by earthquakes undersea or below coastal areas.
Tsunami Video
Fires:
Usually occurs from shifting of subsurface utilities (gas lines)

34. Questions? 34

35. Reflection What is an earthquake? What causes earthquakes?
List the 3 types of seismic waves, in the order you would experience them.
Why is it important for residents of southern California to know what earthquakes are and to understand their characteristics?
What are the 2 scales used to measure earthquakes?
What are some of the hazards associated with earthquakes?
Pick any topic we have discussed so far this year and explain how it is related to earthquakes. (turn to your neighbor and discuss) 35

36. Reflection
San Francisco earthquake, Inhabitants described a huge roar before the shaking, which lasted about a minute. 36

38. Triangulation
Triangulation is a way of determining something's location using the locations of other things.
It is commonly used by geologists to find the epicenters of Earthquakes

39. How is the Location of an Earthquake Determined?
From the seismograph record called the seismogram, the time delay between P and S wave arrival is measured
Then, seismologists use the Time-Travel Curve to calculate distance to the quake epicenter.  
Plot a circle around each of the seismograph location; in which the radius of circle is the distance to the epicenter.
We must repeat the activity for each of at least three (3) stations to triangulate a point (to find epicenter of quake). 
The circles of the three seismic locations should intersect at a single point. This would be the earthquake epicenter.
Thus, a single point is triangulated and epicenter is located precisely.

40. Seismogram Printout 40

41. Time-Travel Curve 41

42. Triangulation of 3 stations to locate earthquake epicenter