1. Earthquakes USGS Earthquake Hazards Program Earthquake Basics
But maybe some that you haven’t already learned and some great pictures to go with it
Overview:
Global perspective
Plate tectonics
Faults
Real-life examples of faults
Fault rupture movie
Earthquake shaking and effects
Seismic waves, magnitude and location
Faults and earthquakes in our local area
earthquake info on the web
U.S. Department of the Interior
U.S. Geological Survey

2. Bellwork Explain the relationship between stress and strain.
Describe what happens when the stress applied to a rock exceeds the strength of the material.
Illustrate the three major types of boundaries and what geologic feature is found at each.

3. Plate Boundaries
Three types of interactions between plates as they move around:
Sliding past one another - transform boundary
Running into one another - convergent boundary
Moving away from one another - divergent boundary

4. Plate Tectonics Lisa Wald USGS Earthquake Hazards Program
USGS Pasadena
Pattern of earthquakes defines the boundaries of tectonic plates
About 23 major plates
Can you see where we are?
Boundary between two plates
We’ll come back to this later
U.S. Department of the Interior
U.S. Geological Survey

5. Global Distribution of Earthquakes
Map of world
Dots are earthquakes
Not scattered all over the world, but make a pattern

6. Pacific-North American Plate Boundary
LA on Pacific Plate
San Francisco on North American Plate
San Andreas Fault is boundary
Relative motion
Takes Big Bend above LA area and causes compression in our area

7. The San Andreas Fault

8. Three Types of Faults Strike-Slip Reverse Normal Three types of faults
Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks
Strike-slip
Normal
Thrust
Normal

9. Strike-slip Fault Example
Strike-slip example
moletrack

10. Strike-slip Fault Example
Before earthquake manure pile was under window where farmer shoveled it out from inside
Fault runs right under corner of barn
After earthquake manure pile moved over about 10 feet
1906 San Francisco Earthquake

11. Normal Fault Example Dixie Valley-Fairview Peaks, Nevada earthquake
December 16, 1954

12. Reverse Fault Example

14. Is there such a thing as “Earthquake Weather”???
No!

15. Bigger Faults Make Bigger Earthquakes
Y axis is length of fault
X axis is magnitude of earthquake

16. Bigger Earthquakes Last a Longer Time
Y axis is how many seconds the earthquake lasts
X axis is the magnitude of the earthquake

18. Questions to think about while viewing:
View EQ Damage
Questions to think about while viewing:
What is released when an EQ occurs?
Where does this energy go?
How do we record the information about this energy?

19. What are seismic waves?

20. What are the differences in these waves?
Which wave will arrive at a location first?
Do the waves leave the EQ focus at different times?
Describe the speed of the two waves.
Are these waves found on the surface of the Earth or the interior?

21. Seismic Waves

23. Primary Wave
- Fast wave!

24. Secondary Waves
Can only travel through solid material

25. Long Wave (or L wave)
- Converted S & P wave energy
- Slowest wave

26. Summary Secondary waves do not travel through liquids, only solids
Primary waves arrive first, followed by Secondary waves.
Seismologists know how fast seismic waves travel, and this helps locate earthquakes.

27. Earthquake Effects - Ground Shaking
Northridge earthquake 1994
Parking garage at Cal State Northridge
Northridge, CA 1994

28. Earthquake Effects - Ground Shaking
Northridge, CA 1994

29. Earthquake Effects - Ground Shaking
Loma Prieta, CA 1989
KGO-TV News ABC-7

30. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

31. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

32. Earthquake Effects - Surface Faulting
Landers, CA 1992

33. Earthquake Effects - Liquefaction
Source: National Geophysical Data Center
Niigata, Japan 1964

34. Earthquake Effects - Landslides
Source: National Geophysical Data Center
Turnnagin Heights,Alaska,1964

35. Earthquake Effects - Fires
Loma Prieta, CA 1989
KGO-TV News ABC-7

36. Earthquake Effects - Tsunamis
1957 Aleutian Tsunami
Photograph Credit: Henry Helbush. Source: National Geophysical Data Center

37. Lag Time!

38. Earthquake Location

39. Locating an EQ epicenter

41. Earthquake Magnitude M5 M6 M7

48. Scales to measure Earthquakes
Richter Scale
Modified Mercalli Scale
Moment Magnitude Scale

49. An Earthquake has occurred!
USGS needs YOUR help to determine where it has taken place.
One seismic station in Detroit, MI has reported that the EQ epicenter is 15 km from their station.

50. An Earthquake has occurred!
Can we locate the EQ epicenter? Why or why not?
Do we have anything to work with to determine where the EQ was located? What should we do?

51. An Earthquake has occurred!
Another seismic station in Charleston, SC has reported that the EQ epicenter is 65 km from their station.

52. An Earthquake has occurred!
Can we locate the EQ epicenter? Why or why not?
Are we any closer to determining this?
What do we still need?

53. An Earthquake has occurred!
A third seismic station in Minneapolis, MN has reported that the EQ epicenter is 48 km from their station.

54. Can we locate this earthquake??
YES!!

55. Will California eventually fall into the ocean???
No!

56. Faults of Southern California
San Andreas Fault in red
Point out other major faults
Source: SCEC Data Center

57. Shaking Hazard in Southern California

58. Faults in Our Local Area - Arcadia
Sierra Madre Fault Zone
THRUST fault
55 KM long
Last ruptured in last 10,000 YEARS
SLIP RATE: between 0.36 and 4 mm/yr
PROBABLE MAGNITUDES: MW (?)
Dips to the north
Source: SCEC Data Center

59. Faults in Our Local Area - Arcadia
Raymond Fault
STRIKE-SLIP fault
26 KM long
Last ruptured in last 10,000 YEARS
SLIP RATE: between 0.10 and 0.22 mm/yr
Source: SCEC Data Center
PROBABLE MAGNITUDES: MW
Dips to the north
At least eight surface-rupturing events have occurred along this fault in the last 36,000 years

60. Faults in Our Local Area - Arcadia
Clamshell-Sawpit Canyon fault
THRUST fault
18 KM long
Last ruptured in last 1.6 million YEARS
SLIP RATE: ???
PROBABLE MAGNITUDES: ???
Dips to the north
Source: SCEC Data Center

61. Real-time Earthquake Information
Can’t predict earthquakes
But we can tell you a lot about one that just happened
Within minutes after it happened
All info on the web.
Plot from last Thursday
How many earthquakes happen each day in CA? ~60

62. ShakeMaps

63. Did You Feel It?
Community
Internet
Intensity
Maps

64. The End Where to go for more information: http://pasadena.wr.usgs.gov/
USGS Earthquake Hazards Program
U.S. Department of the Interior
U.S. Geological Survey
Where to go for more information:
The End

66. Faults in Our Local Area - La Canada
TYPE OF FAULTING: reverse
LENGTH: the zone is about 55 km long;
total length of main fault segments is about 75 km,
with each segment measuring roughly 15 km long
MOST RECENT SURFACE RUPTURE: Holocene,
10,000 years to present
SLIP RATE: between 0.36 and 4 mm/yr
INTERVAL BETWEEN SURFACE RUPTURES:
several thousand years (?)
PROBABLE MAGNITUDES: MW (?)
OTHER NOTES: This fault zone dips to the north.
Source: SCEC Data Center