1. Earthquakes 101 (EQ101) Lisa Wald USGS Earthquake Hazards Program
USGS Pasadena
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. Global Distribution of Earthquakes
Map of world
Dots are earthquakes
Not scattered all over the world, but make a pattern

3. 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

4. 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

6. Three Types of Faults Strike-Slip Thrust 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

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

8. 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

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

10. Thrust Fault Example

11. Thrust Fault Example

13. Total Slip in the M7.3 Landers Earthquake
Rupture on a Fault
Total Slip in the M7.3 Landers Earthquake
Total distribution of slip after earthquake happened.
Red is a lot of slip, blue is no slip
You can see that the whole surface did not slip the same amount
Nor did it slip all at the same time, as you will see in this movie

14. Slip on an earthquake fault
START
Surface of the earth
Depth
Into the
earth 
Snapshots every 2 seconds during the rupture
Starts in southern part of fault
100 km (60 miles)
Distance along the fault plane

15. Slip on an earthquake fault Second 2.0

16. Slip on an earthquake fault Second 4.0

17. Slip on an earthquake fault Second 6.0

18. Slip on an earthquake fault Second 8.0

19. Slip on an earthquake fault Second 10.0

20. Slip on an earthquake fault Second 12.0

21. Slip on an earthquake fault Second 14.0

22. Slip on an earthquake fault Second 16.0

23. Slip on an earthquake fault Second 18.0

24. Slip on an earthquake fault Second 20.0

25. Slip on an earthquake fault Second 22.0

26. Slip on an earthquake fault Second 24.0

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

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

29. What Controls the Level of Shaking?
Magnitude
More energy released
Distance
Shaking decays with distance
Local soils
amplify the shaking

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

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

32. Earthquake Effects - Ground Shaking
Northridge, CA 1994

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

34. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

35. Earthquake Effects - Ground Shaking
Kobe, Japan 1995

36. Earthquake Effects - Surface Faulting
Landers, CA 1992

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

38. Earthquake Effects - Landslides
Source: National Geophysical Data Center
Turnagain Heights, Alaska,1964 (upper left inset);
Santa Cruz Mtns, California , 1989

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

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

41. Seismic Waves

42. Earthquake Magnitude M5 M6 M7

43. Earthquake Location

44. The San Andreas Fault

45. 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

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

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

48. Shaking Hazard in Southern California

49. 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

50. 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

51. 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

52. 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

53. ShakeMaps

54. Did You Feel It?
Community
Internet
Intensity
Maps

55. 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

57. 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