Earthquakes occur due to the buildup and sudden release of energy along fault lines in the Earth's crust. When pressure becomes too great, the plates jerk past one another causing violent shaking at the epicenter and releasing seismic waves that spread outwards. The three main types of faults are normal, reverse, and strike-slip, which control how the plates move during an earthquake. Understanding earthquake hazards and being prepared can help reduce risks to safety when they occur.

1. welcome

3. “An earthquake is the
motion or trembling of
the ground produced by
sudden displacement of
rock in the Earth's crust.
Earthquakes result from
crustal strain, volcanism,
landslides, and collapse
of cavern”

4. Stage 1: Two of the crusts
plates rub against each
other and stick in one
place. Pressure builds up as
they try and move past
each other.
Stage 2: Suddenly, the
pressure is too much
and the plates jerk
past each other. The
place where this
happens is called the
focus.
Why do earthquakes
happen?

5. Stage 3: Vibrations go out in all
directions through the rocks.
These vibrations are called
shockwaves or seismic waves
Stage 4: When the shock waves
reach the surface of the earth they
cause the ground to shake. The
most violent shaking is directly
above the focus at a point on the
Earths surface called the
epicentre.
focus
epicenter

6. Where do earthquakes occur:
1) Most earthquakes occur along the edge of the
oceanic and continental plate

7. Why do earthquakes happen?

8. Elastic Rebound

9. Definitions
• Earthquake = Vibration of the Earth
produced by the rapid release of energy
• Seismic waves = Energy moving outward
from the focus of an earthquake
• Focus= location of initial slip on the
fault; where the earthquake origins
• Epicenter= spot on Earth’s surface
directly above the focus

12. Stress and Strain along faults

13. Faults
A fault is a large crack in the Earth's crust where one
part of the crust has moved against another part.
There are three basic fault types
1. Normal faults: form when the
hanging wall drops down.
The forces that create
normal faults are pulling
the sides apart, or
extensional.

14. Fault Type2
2. Reverse faults form
when the hanging wall
moves up.
The forces creating reverse
faults are compressional,
pushing the sides together.

15. Fault Type33. Strike-slip faults
have walls that move sideways,
not up or down.
That is, the slip occurs along
the strike, not up or down the
dip.
In these faults the fault plane is
usually vertical, so there is no
hanging wall .

16. FAULTS

17. Faults

18. Normal Fault

20. Reverse Fault

22. Strike-Slip
Fault

23. Strike Slip
Fault

24. Seismic waves: forms
• P-waves:
– called compressional, or push-pull waves
– Propagate parralel to the direction in which the wave is moving
– Move through solids, liquids
• S-waves:
– Called shear waves
– Propagate the movement perpendicular
to the direction in which the wave is
moving
• Surface waves (L-waves or long waves).
– Complex motion
– Up-and-down and side-to-side
– Slowest
– Most damage to structures, buildings

25. P-Wave Motion
Push-Pull Motion

26. S-Wave Motion
S-shake or shear wave

27. Earthquake Waves

28. Seismic Wave Motion

29. Major Hazards of Earthquakes
• Building Collapse
• Landslides
• Fire
• Tsunamis
4”

30. Building Collapse
.” Earthquakes don’t kill people, buildings kill people

31. Landslides

32. Fire
Great Alaska Earthquake
March 28, 1964
Valdez, Alaska
Magnitude 8.4

33. Tsunamis

34. Tsunami

35. Measuring earthquakes
• Seismometers:
instruments that detect
seismic waves
• Seismographs
Record intensity, height
and amplitude of seismic
waves

36. Richter Scale
• Henry richter
(1918-1992)
• Measures the energy or
strength released by
earthquake movement
• Provides accurate
measurements for small,
nearby earthquakes
Does not work for big, far ones

37. 2) Intensity: Mercalli Scale:
– What did you feel?
– Assigns an intensity or rating to measure an earthquake at
a particular location (qualitative)
– (buildings nearly destroyed)
– Measures the destructive effect
• Intensity is a function of:
• Energy released by fault
• Geology of the location
• Surface substrate: can magnify shock waves e.g. Mexico
City (1985) and San Francisco (1989)

38. Seismographs

39. • Develop home earthquake plan
• Conduct earthquake drills
• Develop plan for reuniting family members
• Develop family communication plan
• Keep supplies on hand
CERT Basic Training
Unit 1: EarthquakesE-40
Earthquake Preparedness

40. • First:
– Check selves for injuries
– Protect selves from further danger
• Then:
– Extinguish small fires
– Clean up spills
– Inspect home for damage
– Help neighbors
– Tune to Emergency Alert System (EAS)
– Expect aftershocks
CERT Basic Training
Unit 1: EarthquakesE-41
After an Earthquake

41. • Drop, cover, and hold
• If indoors, stay there until shaking stops
• If outdoors, find a spot away from buildings,
trees, streetlights, power lines, and
overpasses
• If in a vehicle, drive to clear spot and stop
CERT Basic Training
Unit 1: EarthquakesE-42
During an Earthquake

42. • First:
– Check selves for injuries
– Protect selves from further danger
• Then:
– Extinguish small fires
– Clean up spills
– Inspect home for damage
– Help neighbors
– Tune to Emergency Alert System (EAS)
– Expect aftershocks
CERT Basic Training
Unit 1: EarthquakesE-43
After an Earthquake

43. Construction against earthquake

44. Frequencyof Occurrence of Earthquakes
Descriptor Magnitude Average Annually
Great 8 and higher 1 ¹
Major 7 - 7.9 17 ²
Strong 6 - 6.9 134 ²
Moderate 5 - 5.9 1319 ²
Light 4 - 4.9
13,000
(estimated)
Minor 3 - 3.9
130,000
(estimated)
Very Minor 2 - 2.9
1,300,000
(estimated)
¹ Based on observations since 1900.
² Based on observations since 1990.

45. Recent Earthquake Activity in the
World

47. Most Destructive Known Earthquakes on Record in the World
Date Location Deaths Magnitude Comments
May 31, 1970 Peru 66,000 7.9 $530,000,000
damage, great rock
slide, floods.
July 27, 1976 China,
Tangshan
255,000
(official)
7.5 Estimated death toll as
high as 655,000.
Sept 19, 1985 Mexico
Michoacan
9500
(official)
8.0 Estimated death toll as
high as 30,000
Old lake bed magnified
shock waves by 500%
2001 Jan 26 India 20,023 7.7 166,836 injured,
600,000 homeless
.
2004 Dec 26 Sumatra 283,106 9.0 Deaths from earthquake
and tsunami

48. Largest earthquake in the world
Chile : 1960 May 22
19:11:14 UTC
Magnitude 9.5
More than 2,000 killed, 3,000 injured, 2,000,000
homeless, and $550 million damage in southern
Chile
tsunami caused 61 deaths
$75 million damage in Hawaii;
138 deaths and $50 million damage in Japan;
32 dead and missing in the Philippines;
and $500,000 damage to the west coast of
the United States.

49. Jun 23, 2001 S.Peru earthquake
Arequipa

50. Dead - More than 3,000
•A report of U.S. Army
relief operations recorded:
•498 deaths in San
Francisco
•64 deaths in Santa
Rosa
•102 deaths in and near
San Jose
Stanford University 1906 Earthquake
damage.

51. Earthquake damage in Anchorage on March 27, 1964

52. San Francisco are built on sandy soil or fill. Many homes built on this type of
soil were badly damaged during the 1989 Loma Prieta earthquake.

53. Tsunami Damage,
Gleebruk, Indonesia

54. India, Gujarat earthquake
Jan 26, 2001

55. Be smart About
Earthquake Safety