1. CHAPTER 19
EARTHQUAKES

2. The following words are on the quiz Friday 11/16/07
fault
primary wave
secondary wave
surface wave
focus
epicenter
seismometer
magnitude
tsunami
seismogram

3. I. Forces Inside Earth
A. Causes of Earthquakes
1. stress of pressure is put on rocks
2. The rock layers bend until they reach their elastic limit
3. Once their limit is exceeded the rocks break
a) fault: a break or crack in a rock where movement occurs
4. This breaking produces vibrations called earthquakes

4. B. Forces in the Earth
1. Compression: forces or stress that squeezes or compresses
2. Tension: stress that causes stretching & elongation
3. Shear: forces that causes slipping
a) causes rocks on either side of a fault to move past each other

5. C. Types of Faults
1. Normal Fault
a) Tension pulls the rocks apart
b) Rock above the fault surface moves downward in relation to rock below the fault surface

6. NORMAL FAULT

7. 2. Reverse Fault
a) Compression Pushes on Rocks from opposite directions
b) Rocks above the fault surface are forced up & over rocks below the fault surface

8. REVERSE FAULT

9. 3. Strike-Slip Fault
a) Shear forces cause rocks to slide past each other
b) rocks on either side of the fault are moving past each other without much upward or downward movement
c) Ex. San Andreas Fault, CA

10. STRIKE-SLIP FAULT

11. 4. Earthquakes occur as pressure builds up
in these faults and the rocks
finally break.

12. Use your notes to answer the following
1. List three forces inside the Earth
2. What type of force causes a strike-slip fault?
3. What type of force causes a normal fault?
4. What type of force causes a reverse fault?

13. II. Earthquake Information
A. Types of Seismic Waves
1. Seismic Wave
a) Energy waves generated by an earthquake
2. Focus
a) point on the Earth’s surface where seismic waves start
b) place where the energy is released
c) Epicenter- point on the Earth’s surface directly above the focus

14. 3. Primary Waves (P-waves)
a) cause particles & rocks to compress & stretch apart in the same
direction of the wave.
b) can travel through solid, liquid, & air
c) the fastest wave 6km/sec or 21,600km/hr or 12,960mph

15. P-WAVES

16. 4. Secondary Waves (S-waves)
a) cause rocks to move at right angles to the direction of the wave.
b) can only travel through solids
c) second fastest wave 3.5km/sec or 12,600km/hr or 7560mph

17. S-WAVES

18. 5. Surface Waves
a) surface waves start at the epicenter
b) the waves move up & down & side to side
c) Ex. L-wave: move up and down
d) slowest wave 2.0km/sec or 7200km/hr or 4320 mph

19. SURFACE WAVES

20. Answer the following in your notes
1. List three types of seismic waves?
2. Which seismic wave can only travel through solids?
3. What force causes a reverse fault?
4. What force causes a strike-slip fault?
5. What force causes a normal fault?

21. B. Locating an Epicenter
1. Seismograph Station
a) records the arrival of earthquake waves
b) P-waves arrive 1st, S-waves second
c) P-S wave graph pg 501

22. 2. How to locate an epicenter
a) 3 stations are needed
b) the distance from the Earthquake is used to find the epicenter

23. LOCATING AN EPICENTER

24. EARTH’S INTERIOR

25. C. Mapping Earth’s Interior
1. Inner Core
a) Solid Dense
b) composed of Iron and Nickel
2. Outer Core
a) Liquid
b) composed of Iron & Nickel

26. 3. Mantle
a) Is directly above the outer core
b) the largest layer in the Earth
c) composed of silicon, oxygen, magnesium, & iron

27. 4. Crust
a) Outermost layer of the Earth
b) separated from the mantle by the Moho Discontinuity
5. Moho Discontinuity
a) layer that lies between the crust and the upper mantle
b) P & S wave slow down because this layer is partially melted
c) was discovered by Andrija Mohorovicic

28. 6. Shadow Zone
a) located 105o to 140o from the focus
b) no earthquake waves are detected there
c) liquid outer core prevents S-waves from going through the Earth
d) P-waves slow down & are deflected away from` the outer core

29. SHADOW ZONE

30. III. Destruction by Earthquakes
A. Measuring Earthquakes
1. Seismology
a) seismologist: scientist who studies earthquakes
b) seismograph: records primary, secondary, and surface waves

31. SEISMOGRAPH

32. B. Earthquake Magnitude
1. Richter Scale
a) describes how much energy is released by an Earthquake
b) Each degree of magnitude is 32 times greater than the one before
c) 5.5 – 6.5 = 32 times stronger
5.5 – times stronger (322)

33. 2. Moment magnitude Scale
a) looks at fault size
b) measures how much movement occurred
c) how stiff are the rocks?
d) the number is an average of several seismic waves

34. 3. Modified Mercalli Scale
a) Measures the amount of damage
b) I (little damage) XII (total destruction)

35. 4. Depth of Focus
a) Ranked as shallow, intermediate or deep
b) devastating earthquakes are always shallow focus

36. C. Tsunamis (Tidal Wave)
1. Caused by an Earthquake under the ocean
2. The quick movement pushes against the water creating a powerful wave
3. These waves can be over 30m (80ft) high when they reach the surface.

37. Use your notes to answer the following
1. How many seismometer stations are needed to locate an earthquake epicenter?
2. Which type of earthquakes are more devastating, shallow focus or deep focus earthquakes?
3. What causes a tsunami?

38. Use your notes to answer the following
1. When an area experiences an earthquake, which waves arrive first, P, S, or surface waves?
2. Which earthquake waves cause the most damage at the epicenter?
3. Explain the difference between an earthquake focus and an earthquake epicenter.
4. List three scales that describe earthquake magnitude and/or damage.

39. Use your notes to answer the following
1. Which earthquake waves cause the most damage at the epicenter?
2. Explain the difference between an earthquake focus and an earthquake epicenter.
3. List three scales that describe earthquake magnitude and/or damage.

40. When the force on rocks is great enough, they break, producing vibrations called ____.
a. faults c. strains
b. earthquakes d. stresses

41. Once the elastic limit of rocks is passed, they break and move along surfaces called ____.
a. faults c. strains
b. earthquakes d. stresses

42. The height of the lines traced on paper is a measure of the energy released or the ____ of the earthquake.
a. stress c. magnitude
b. strain d. intensity

43. Most earthquakes happen ____.
a. without warning
b. in areas where earthquakes have occurred in the past
c. along plate boundaries
d. all of the above

44. Scientists discovered changes in Earth's interior by studying ____.
a. tsunamis c. changes in seismic waves
b. tides d. all of the above

45. ____ is the force that squeezes rocks together.
a. Tension c. Elastic limit
b. Shear d. Compression

46. ____ is the force that pulls rocks apart.
a. Tension c. Elastic limit
b. Shear d. Compression

47. ____ is the force that causes plates to move sideways past each other.
a. Tension c. Elastic limit
b. Shear d. Compression

48. ____ faults are caused by tensional forces.
a. Normal c. Reverse
b. Strike-slip d. Elastic

49. ____ faults are caused by compressional forces.
a. Normal c. Reverse
b. Strike-slip d. Elastic

50. ____ faults are caused by shear forces.
a. Normal c. Reverse
b. Strike-slip d. Elastic

51. Along a(n) ____ fault, rock above the fault surface moves downward in relation to rock below the fault surface.
a. normal c. elastic
b. reverse d. strike-slip

52. Along a(n) ____ fault, rock above the fault surface moves upward in relation to rock below the fault surface.
a. normal c. elastic
b. reverse d. strike-slip

53. At a(n) ____ fault, rocks on either side of the fault surface move past each other.
a. normal c. reverse
b. elastic d. strike-slip

54. The most destructive seismic wave are ____.
a. primary waves c. P-waves
b. secondary waves d. surface waves

55. The ____ waves are the first to reach a seismograph after an earthquake.
a. surface c. primary
b. secondary d. tsunami

56. At least ____ seismographs are needed to accurately locate an earthquake epicenter.
a. two c. four
b. five d. three

57. The point in Earth's interior where the energy release of an earthquake occurs is the ____.
a. focus c. fault
b. epicenter d. inner core

58. Seismic waves ____ when they reach the bottom of the crust.
a. slow down c. stop
b. stay the same d. speed up

59. The magnitude of an earthquake is measured by the ____.
a. Richter scale c. modified Mercalli scale
b. moho discontinuity d. elastic limit

60. Primary waves ____ when they hit the liquid outer core.
a. slow down c. stop
b. stay the same d. speed up

61. Secondary waves ____ when they hit the liquid outer core.
a. slow down c. stop
b. stay the same d. speed up

62. A ____ fault forms as a result of horizontal compression.
a. blind c. strike-slip
b. normal d. reverse

63. The San Andreas Fault, a result of horizontal shear, is a ____ fault.
a. blind c. strike-slip
b. normal d. reverse

64. The locations of seismic belts are determined by plotting ____.
a.earthquake epicenters
b.seismic gaps c.earthquake foci
d.epicentral

65. Deaths associated with earthquake deaths in sloping areas can result from ____.
a. tsunamis c. formation of fault scarps
b. landslides d.surface ruptures

66. Seismic waves generated by an earthquake at point R are recorded at locations W and X.
Which pair of seismographs is more accurate? A C B D

67. A a line of Earth’s magnetic field
Each dot on the above diagram marks the origin of an earthquake. The area with the highest concentration of earthquake origins marks —
A a line of Earth’s magnetic field
B a seam of soft rock, such as limestone
C the path of the subducting tectonic plate
D the location of a developing igneous intrusion .

68. The diagram shown illustrates which geological process?
A Faulting
B Folding
C Weathering
D Metamorphism

69. One part of California is on the Pacific Plate, while the remainder of the state is on the North American Plate. The two plates are moving to the northwest at different speeds, causing one plate to slide past the other. This movement in plates creates a —
A normal fault
B reverse fault
C strike-slip fault
D thrust fault

70. What is usually responsible for an earthquake?
A Pressure buildup within the mantle
B Slippage along faults within Earth’s crust
C Weathering along coastlines
D Force changes from the moon pulling on Earth

71. The formations at X and Y in the picture above were created by —
A tension
B shearing
C compression
D rifting

72. The edges of moving crustal plates are often defined by —
A ocean basins
B frequent seismic activity
C intercontinental plains
D Earth’s largest rivers

73. An earthquake struck San Diego, California
An earthquake struck San Diego, California. The above map and table show that the approximate difference in arrival times between the P-wave and S-wave at Seattle is —
A 2 minutes
B 3 minutes
C 4 minutes
D 5 minutes

74. The point from which an earthquake originates is called the —
A focus
B epicenter
C fault line
D shock wave

75. What is the fewest number of seismographic stations that must record the arrival time of P and S waves in order for the epicenter of an earthquake to be located?
A 2
B 3
C 5
D 10