1. Standard 8-3.8
EARTHQUAKES

2. Assessing Prior Knowledge and Relativity
What have you heard about earthquakes lately?
Why should we study earthquakes?

3. Falcon Focus
8-1.1 The standard metric unit of length used in a science lab is…
a. Celsius
b. Gram
c. Liter
d. Meter

4. What causes earthquakes and where do they happen?
Essential Question
What causes earthquakes and where do they happen?

5. Earthquakes!

6. INTRODUCTION

7. Deadliest Earthquakes
The earthquake that caused the most destruction in history occurred in the Shansi province of China on January 23, An estimated 830,000 people were killed.
The second most destructive earthquake also occurred in China--in July, and killed 255,000 people.

8. What is an Earthquake?
The definition of an earthquake is… vibrations that cause the breaking of rocks.
These vibrations move in all directions through the earth. They begin at a point along a fault.

9. Earthquakes
Forces___ and __Stresses__ (8-3.7– tension, compression, and shearing) along faults can build up as blocks of rock are pushed (compression or shearing) or pulled apart (tension). If the __pressure___ or stress becomes too great, the rock breaks at a weak point along the fault and ___energy_____ is released

10. Earthquakes
____Earthquakes_____ are vibrations produced when rocks break along a ___fault_____. The term earthquake describes the sudden slip on a fault and includes the ground shaking and radiating _____seismic waves___ that is caused by the slip.  ___Volcanic Activity____, or other geologic processes, may cause stress changes in the earth that can also result in an earthquake.

11. How do faults form?
The earth’s crust is constantly experiencing pressure from forces within and around it. This pressure builds up over time, and eventually causes the crust to break. This becomes a fault.
Let’s experience it…

12. Kinds of Faults... Faults are divided into three main groups:
Normal fault - when two plates are moving apart and one side of the fracture moves below the other; (caused by tension forces!)
Reverse fault - when two plates collide and one side of the fracture moves on top of another; (caused by compression forces!!)
Strike-slip - when two plates slide past each other. (caused by shear forces!)

13. 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 13

14. What is an Earthquake?
An earthquake begins along a fault (a crack in the earth’s surface) at a point called the focus.
Directly above the focus is a point on the earth’s surface called the epicenter.

15. Where does an earthquake begin?
Epicenter
Focus

16. Why is the epicenter important?
Seismologists have stations all over the world that continuously collect information about earthquakes. This kind of information can help scientists figure out where larger, more destructive earthquakes may strike by mapping out the location of smaller ‘quakes. They also get a greater understanding of the changes the earth’s crust makes as the earthquakes occur.
How do they do this???

17. What is an Earthquake?
When the fault ruptures with a sudden movement energy is released that has built up over the years. This energy is released in the form of vibrations called 'seismic waves'… earthquakes!
It is actually when these seismic waves reach the surface of the earth that most of the destruction occurs, which we associate with earthquakes.

18. Parts of the Earthquake
The energy spreads outward in all directions as vibrations called ____seismic waves_____.
The _focus____ of the earthquake is the point in the crust, or mantle, where energy is released.
The _epicenter___ is the point on Earth’s surface directly above the focus; energy that reaches the surface is greatest at this point.

19. Focus –. point inside the Earth where an
Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

20. Focus, Epicenter, and Fault

21. WHAT CAUSES EARTHQUAKES?
Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip
Caused by volcanic or magmatic activity,
Caused by other sudden stress changes in the earth.

22. What causes earthquakes?
Tectonic plates move past each other causing stress. Stress causes the rock to deform

24. What Causes an Earthquake?
Cause of Earthquakes
What Causes an Earthquake?
 Aftershocks and Foreshocks
• An aftershock is a small earthquake that follows the main earthquake.
• A foreshock is a small earthquake that often precedes a major earthquake.

25. What Kind of Damage Do They Do?
Earthquakes can also cause landslides, sudden eruptions as in the case of a hot lava flow from a volcano or giant waves called tsunamis. Sometimes new land mass are also formed. Such earthquakes are attributed with the creation of the greatest undersea mountain range and the longest land mountain range.

26. Landslides & Tsunamis

27. San Francisco, 1989

28. San Francisco, 1989

29. San Francisco, 1989

30. San Francisco, 1989

31. San Francisco, 1989

32. San Francisco, 1989

33. San Francisco, 1989

34. San Francisco, 1989
…And that was just a 7.2 on the Richter scale!

35. Haiti 2010

38. What Does an Earthquake
Feel Like?
Generally, during an earthquake you first will feel a swaying or small jerking motion, then a slight pause, followed by a more intense rolling or jerking motion. The duration of the shaking you feel depends on the earthquake's magnitude, your distance from the epicenter, and the geology of the ground under your feet.

39. How Long Does an Earthquake Last?
For minor earthquakes, ground shaking usually lasts only a few seconds.
Strong shaking from a major earthquake usually lasts less than one minute. For example, shaking in the 1989 magnitude 7.1 Loma Prieta (San Francisco) earthquake lasted 15 seconds;
For the 1906 magnitude 8.3 San Francisco earthquake it lasted about 40 seconds.
Shaking for the 1964 magnitude 9.2 Alaska earthquake, however, lasted three minutes.

40. Earthquake Predictors?
Often, earthquakes can be a sign of things to come, like in the case of Mt. St. Helen’s in Washington.

41. Mt. St. Helens
At 8:32 Sunday morning, May 18, 1980, Mount St. Helens erupted.
Shaken by an earthquake measuring 5.1 on the Richter scale, the north face of this tall symmetrical mountain collapsed in a massive rock debris avalanche. Nearly 230 square miles of forest was blown over or left dead and standing. At the same time a mushroom-shaped column of ash rose thousands of feet skyward and drifted downwind, turning day into night as dark, gray ash fell over eastern Washington and beyond. The eruption lasted 9 hours, but Mount St. Helens and the surrounding landscape were dramatically changed within moments.

42. Mt. St. Helens This photograph was taken during the 1980 eruption.
Is this volcano active again??? The seismic data says…YES!

43. Mt. St. Helens
After
Before

44. Notice, this volcano really blew its top… literally!
Volcanoes...
Notice, this volcano really blew its top… literally!
Mt. St. Helens Today

45. Focus, Epicenter, and Fault

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

47. Where Do Earthquakes Occur and How Often?
~80% of all earthquakes occur in the circum-Pacific belt
most of these result from convergent margin activity
~15% occur in the Mediterranean-Asiatic belt
remaining 5% occur in the interiors of plates and on spreading ridge centers
more than 150,000 quakes strong enough to be felt are recorded each year

48. Review!!! http://www.iknowthat.com/mhscience/Earthquakes/Fixed.htm

49. Focus and Epicenter of Earthquake

50. HOMEWORK .

51. FALCON FOCUS
THE POINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________.
THE EPICENTER
THE FOCUS
THE ASTHENOSPHERE
THE FAULT

52. FALCON FOCUS
THE POINT ON EARTH’S SURFACE WHERE THE GREATEST ENERGY FROM THE EARTHQUAKE IS RELEASED IS ___________.
THE EPICENTER
THE FOCUS
THE ASTHENOSPHERE
THE FAULT

53. ESSENTIAL QUESTION
HOW WOULD YOU COMPARE AND CONSTRAST THE THREEE TYPES OF SEISMIC WAVES?

54. INTRODUCTION
IN A POP AND LOCK DANCE MOVE, STUDENTS WILL DEMONSTRATE THE 3 TYPES OF SEISMIC WAVES

55. SEISMIC WAVES
_SEISMIC WAVES___ are waves generated by an earthquake that travel through the Earth. These waves can cause the ground to move forward, backward, up, down, and even to ripple. Seismic Waves are generated at the __SAME___ time but move in different ways, and at different speeds.

56. Seismic Waves in the Earth

57. CONSIDERED AS BODY WAVES
3 TYPES OF SEISMIC WAVES
PRIMARY (P) WAVES
SECONDARY (S) WAVES
SURFACE WAVES
CONSIDERED AS BODY WAVES

58. Seismic Waves

59. 8.2 Measuring Earthquakes
Earthquake Waves
8.2 Measuring Earthquakes
 Body Waves
• Identified as P waves or S waves
• P waves
- Are push-pull waves that push (compress) and pull (expand) in the direction that the waves travel
- Travel through solids, liquids, and gases
- Have the greatest velocity of all earthquake waves

60. PRIMARY (P) WAVE
Move out from the earthquake focus, the point where the energy is released
Travel the fastest of the three waves
Move through solid and liquid layers of Earth (it also can move in gas)
Push and pull rock creating a back-and-forth motion in the direction the wave is moving (longitudinal wave)

61. Primary Waves (P Waves)
A type of seismic wave that compresses and expands the ground
The first wave to arrive at an earthquake

62. 8.2 Measuring Earthquakes
Earthquake Waves
8.2 Measuring Earthquakes
 Body Waves
• S waves
Seismic waves that travel along Earth’s outer layer
- Shake particles at right angles to the direction that they travel
- Travel only through solids
- Slower velocity than P waves
 A seismogram shows all three types of seismic waves—surface waves, P waves, and S waves.

63. Secondary Waves (S Waves)
Move out from the earthquake focus
Move slower than primary waves
Can only move through solid rock
Move at right angles to primary waves causing rocks to move up and down and side to side (transverse wave)

64. Secondary Waves (S Waves)
A type of seismic wave that moves the ground up and down or side to side

65. Body Waves: P and S waves
P or primary waves
fastest waves
travel through solids, liquids, or gases
compressional wave, material movement is in the same direction as wave movement
S or secondary waves
slower than P waves
travel through solids only
shear waves - move material perpendicular to wave movement

67. Comparing Seismic Waves

68. SURFACE WAVES Form when P and S waves reach the surface
Can cause the ground to shake making rock sway from side to side and roll like an ocean wave
These waves cause the most destruction
They move back and forth and in a rolling motion along the surface
They release all of the energy of the earthquake

69. Surface Waves: R and L waves
Travel just below or along the ground’s surface
Slower than body waves; rolling and side-to-side movement
Especially damaging to buildings

70. Surface Waves Move along the Earth’s surface
Produces motion in the upper crust
Motion can be up and down
Motion can be around
Motion can be back and forth
Travel more slowly than S and P waves
More destructive

72. Seismic Waves Paths Through the Earth

73. Earth’s Interior Showing P and S Wave Paths

74. Scientists use the principle that the speed and direction of a seismic wave depends on the material it travels through. Because of the behavior of these different waves, scientists have indirect evidence for the solid inner core and liquid outer core of Earth; because earthquake waves travel faster through the mantle than through the crust, scientists know that the mantle is denser than the crust.

75. Earthquake Waves & Earth’s Interior

76. ACTIVITY
CREATE S, P, AND SURFACE WAVES USING A STRING AND A SLINKY

77. Primary or “P” Wave
Secondary or “S” Wave

78. Measuring Earthquakes
The movement of materials in the __outer_ core (which is a liquid) of the Earth is inferred to be the cause of Earth’s _magnetic field___. A compass needle will align with the lines of force of Earth’s magnetic field. __Iron__ and _Nickel__ are metals that easily magnetize, and are inferred to be the metals in Earth’s core.

79. Measuring Earthquakes
The energy spreads outward in all directions as vibrations called ___Seismic Waves____. Seismic waves can be measured and recorded by a ____seismograph_______.
__Seismographs______ are instruments or a device that detects and records seismic or earthquake waves. It measures the vertical ground motion and the horizontal ground motions (N-S/E-W). It also traces wave shapes onto paper and translates waves into an electronic signal.

80. Measuring Earthquakes
The vibration record, called a seismogram, looks like jagged lines on paper. Seismograms are traces of amplified, electronically recorded ground motion made by seismographs.
Measuring the time between the arrival of the P and S waves determines the distance between the recording seismograph and the earthquake epicenter.

81. Measuring Earthquakes
Earthquake Waves
Measuring Earthquakes
 Seismographs are instruments that record earthquake waves.
 Seismograms are traces of amplified, electronically recorded ground motion made by seismographs.

82. Seismograph

83. Types of Seismographs

85. Seismogram Printout

86. How is an Earthquake’s Epicenter Located?
Seismic wave behavior
P waves arrive first, then S waves, then L and R
Average speeds for all these waves is known
After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.
How is an Earthquake’s Epicenter Located?

87. Determining the location of an earthquake
First, distance to earthquake is determined.
1. Seismographs record seismic waves
2. From seismograph record called the seismogram, measure time delay
between P & S wave arrival
3. Use travel time curve to determine distance to earthquake as function
of P-S time delay
Now we know distance waves traveled, but we don't know the direction from
which they came.
We must repeat the activity for each of at least three (3) stations to
triangulate a point (epicenter of quake).
Plot a circle around seismograph location; radius of circle is the distance to the
quake.
Quake occurred somewhere along that circle.
Do the same thing for at least 3 seismograph stations; circles intersect at epicenter. Thus, point is triangulated and epicenter is located.

88. Locating an Earthquake

89. How is an Earthquake’s Epicenter Located?
Time-distance graph showing the average travel times for P- and S-waves. The farther away a seismograph is from the focus of an earthquake, the longer the interval between the arrivals of the P- and S- waves

90. Time-Travel Curve

91. How is an Earthquake’s Epicenter Located?
Three seismograph stations are needed to locate the epicenter of an earthquake
A circle where the radius equals the distance to the epicenter is drawn
The intersection of the circles locates the epicenter

92. Locating an Earthquake Epicenter
Triangulate means to use three positions to determine an exact location.

93. What is Triangulation?
Triangulation identifies the epicenter of an earthquake. The location of an earthquake’s epicenter is found by plotting circles on a map from the records of three seismograph stations and finding the point where the three circles intersect. Triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly.

94. Locating Earthquakes

95. Locating Earthquakes

96. Locating Earthquakes

97. Triangulation of 3 stations to locate earthquake epicenter

98. How do scientists calculate how far a location is from the epicenter of an earthquake?
Scientists calculate the difference between arrival times of the P waves and S waves
The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

99. How are earthquakes measured?
Earthquakes are measured using the Richter Scale. The strongest earthquake ever measured was a 9.5 on the Richter Scale. This is a measurement of the amount of energy released from the earthquake.

100. 8.2 Measuring Earthquakes
 Historically, scientists have used two different types of measurements to describe the size of an earthquake —intensity and magnitude.
 Richter Scale
• Based on the amplitude of the largest seismic wave
• The _Richter Scale expresses the magnitude of an Earthquake and measures the energy released. The scale goes from 1 to 10 .

101. How are the Size and Strength of an Earthquake Measured?
Magnitude
Richter scale measures total amount of energy released by an earthquake; independent of intensity
Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale

102. Determining the magnitude of an earthquake
Magnitude -- measure of energy released during earthquake.
There are several different ways to measure magnitude.
Most common magnitude measure is Richter Scale, named for the renowned seismologist, Charles Richter.
Richter Magnitude
Measure amplitude of largest S wave on seismograph record.
Take into account distance between seismograph & epicenter.
Intensity
Intensity refers to the amount of damage done in an earthquake

103. How are the Size and Strength of an Earthquake Measured?
Intensity
subjective measure of the kind of damage done and people’s reactions to it
Modified Mercalli Intensity Map
1994 Northridge, CA earthquake, magnitude 6.7

104. How are Earthquakes Measured? Richter Scale

105. Strongest Earthquakes
9.5 Chile, May 22, 1960
9.2 Indian Ocean (Sumatra tsunami) Dec 26,2004
9.2 Prince William Sound, Alaska, March 28, 1964
9.1 Andreanof Islands, Aleutian Islands, Pacific,
March 9, 1957
9.0 Kamchatka, Russia, November 4, 1952
8.8 Off the Coast of Ecuador, January 31, 1906
8.7 Rat Islands, Aleutian Islands, Pacific,
February 4, 1965
8.6 India-China Border, August 15, 1950
8.5 Kamchatka, Russia, February 3, 1923
8.5 Banda Sea, Indonesia, February 1, 1938
8.5 Kuril Islands, Pacific, October 13, 1963

106. Earthquake Waves (Review)
Primary Wave (P-Wave) First set of waves
Move side to side
FASTEST wave
Secondary Wave (S-Wave) Second set of waves
Move up and down
Travel slow
Surface Wave
Move up and down & side to side
MOST DANGEROUS
SLOWEST Wave

107. Closure
Create a Venn Diagram contrasting and comparing the 2 types of seismic waves.

108. Homework Study for Quiz Place the following words in your glossary.
Primary wave, Secondary wave, Surfaces wave, Longitudinal wave, Transverse wave, Richter Scale, Seismograph, Seismogram, Magnitude, and Intensity.

109. FALCON FOCUS
S WAVES CANNOT TRAVEL THROUGH LIQUIDS AND P WAVES SLOW DOWN IN LESS RIGID MATERIALS. IN EARTH’S OUTER CORE, S WAVES CANNOT BE DETECTED AND P WAVES SLOW DOWN. THESE SUGGEST THAT ____.
THE OUTER CORE MAY BE LIQUID
THE OUTER CORE MAY BE SOLID
THERE ARE NO EARTHQUAKES IN THE OUTER CORE
THE OUTER CORE IS THE THICKEST LAYER OF THE EARTH

110. ESSENTIAL QUESTION
IN YOUR OWN WORDS, EXPLAIN HOW SEISMIC WAVES MOVE FROM THE FOCUS OF AN EARTHQUAKE?

111. THE END