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Name: ________________________ Class: ___________________ Date: __________
ID: A
Chapter 9: Earthquakes -- Multi-format Test
Modified True/False
Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true.
____
1. Divergent fault boundaries are especially likely to cause earthquakes. _________________________
____
2. When the kinetic energy built up in a plate exceeds the strength of the rock an earthquake occurs.
_________________________
____
3. Secondary, or S-waves are only able to travel through liquids inside Earth. _________________________
____
4. Seismic waves are recorded and measured by an instrument called a seismologist.
_________________________
____
5. The Mercalli scale rates earthquakes according to the size of the seismic waves recorded on a seismograph.
_________________________
____
6. The San Andreas fault is an active fault that causes many earthquakes to occur in the city of San Francisco,
California. _________________________
Completion
Complete each statement.
Select the correct term to complete each sentence. There are extra terms in the list.
transform
slickenslides
foreshocks
focus
converging
stick-slip
body
epicenter
diverging
aftershocks
surface
fault
7. An earthquake is a form of _________________________ motion.
8. ____________________ plate boundaries are especially likely to cause earthquakes.
9. The ____________________ is the point below the surface where the rock breaks in an earthquake.
10. A ____________________ is a break in the rock of Earth’s surface where movement occurs to cause
earthquakes.
11. Seismic waves are also known as ____________________ waves because they travel through the interior of
Earth.
12. The seismic waves from an earthquake are usually strongest at the ____________________.
13. ____________________-waves cause the most damage to buildings above ground.
Short Answer
14. List the three things that are needed for stick-slip motion.
15. Describe the differences between shallow focus earthquakes and deep focus earthquakes.
16. Describe the movement of P- and S-waves and explain how fast they move in relation to each other.
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17. Why has San Francisco experienced several severe earthquakes and many smaller ones?
18. What type of information does a seismograph give about seismic waves?
19.
The diagram above shows the focus of an earthquake and how its seismic waves travel through the interior of
Earth. Which of the waves is an S-wave and which is a P-wave? Explain how you know.
20. After a minor earthquake, a Los Angeles, California, newspaper’s headline reads: “Blame Plate Tectonics.”
What do you think this means?
Problem
21. Assume that P-waves travel through Earth at an average speed of 6 km/s. A seismic station is located 72 km
from the epicenter of an earthquake. How many seconds did it take for the P-waves to arrive at this seismic
station?
22. The distance scale on a map is 1 centimeter = 25 kilometers. The distance from a seismic station to the epicenter
of an earthquake is 75 kilometers. To locate the epicenter, what would be the radius of the circle that is drawn
around this station on a map?
23. Assume that P-waves travel at an average of 6 km/s and S-waves travel at an average of 4 km/s. The P-waves
from an earthquake reach a seismic station in 7 seconds. How long will it take the S-waves to arrive at this
same station?
24. Assume that P-waves travel at 6 km/s and S-waves travel through Earth at 4 km/s. It takes 13 seconds for the
S-waves to reach the seismic station. How much longer did it take the S-waves to arrive at the station
compared to the P-waves?
Essay
25. Explain in detail what happens when a large earthquake occurs in a city. In your answer be sure to discuss the
different types of seismic waves, foreshocks, and aftershocks. Assume the city receives all types of seismic
waves as well as foreshocks and aftershocks.
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ID: A
Chapter 9: Earthquakes -- Multi-format Test
Answer Section
MODIFIED TRUE/FALSE
1. ANS: F, Transform
PTS: 1
2. ANS: F, potential
DIF: basic
REF: section 9.1
PTS: 1
3. ANS: F, solids
DIF: basic
REF: section 9.1
PTS: 1
DIF: basic
4. ANS: F, seismograph
REF: section 9.2
PTS: 1
5. ANS: F, Richter
DIF: basic
REF: section 9.2
PTS: 1
6. ANS: T
REF: section 9.4
DIF: advanced
REF: section 9.3
PTS: 1
COMPLETION
7. ANS: stick-slip
PTS: 1
8. ANS: Transform
DIF: basic
REF: section 9.1
PTS: 1
9. ANS: focus
DIF: basic
REF: section 9.1
PTS: 1
10. ANS: fault
DIF: basic
REF: section 9.1
PTS: 1
11. ANS: body
DIF: basic
REF: section 9.1
PTS: 1
12. ANS: epicenter
DIF: basic
REF: section 9.2
PTS: 1
13. ANS: Surface
DIF: intermediate
REF: section 9.1
PTS: 1
DIF: intermediate
REF: section 9.2
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DIF: basic
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SHORT ANSWER
14. ANS:
1. Two bodies that are in contact, but are able to move.
2. Forces that will make them move
3. Friction strong enough to stop them from moving at first.
PTS: 1
DIF: intermediate REF: section 9.1
15. ANS:
Shallow focus earthquakes are when the focus of the earthquake is less than 50 kilometers below the surface.
Deep focus earthquakes are when earthquakes occur deeper inside Earth, often at subduction zones.
PTS: 1
DIF: advanced
REF: section 9.1
16. ANS:
P-waves push and pull the rock as it moves through it, in the same direction as the traveling wave. S-waves
cause the rock to move in a side-to-side motion, across the direction of the traveling wave. P-waves travel
faster than S-waves.
PTS: 1
DIF: intermediate REF: section 9.2
17. ANS:
The San Andreas Fault runs directly through the city of San Francisco. The city has experienced several
earthquakes and will continue to experience earthquakes in the future because this is currently a very active
fault.
PTS: 1
DIF: basic
REF: section 9.4
18. ANS:
Seismographs show the kinds of waves that occur, their strength, and the time that they arrive at the
instrument.
PTS: 1
DIF: basic
REF: section 9.2
19. ANS:
Wave A is an S-wave. S-waves cannot travel through the liquid outer core, and are deflected back into the
mantle.
Wave B is a P-wave. P-waves can travel through the liquid outer core.
PTS: 1
DIF: intermediate REF: section 9.2
20. ANS:
California has had another earthquake. California is close to two convergent plates, the Pacific and the North
American. Pressure builds up in Earth’s crust in California, and when the pressure is released, there is an
earthquake. There is also a major fault in California, the San Andreas Fault.
PTS: 1
DIF: intermediate
REF: section 9.3
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ID: A
PROBLEM
21. ANS:
Rate of speed =
distance
time
time =
distance
speed
time =
72 km
= 12 s
6 km/s
PTS: 1
22. ANS:
3 cm
DIF: intermediate
REF: section 9.2
PTS: 1
DIF: intermediate REF: section 9.2
23. ANS:
First find the distance the seismic station is from the epicenter using the following formula:
distance
Rate of speed =
time
distance = speed × time = 6 km/s × 7 s = 42 km
The station is 42 km from the epicenter. Use this and the speed of the S-waves to figure out the time it takes
the S-waves to arrive at the station:
distance
time =
speed
time =
42 km
= 10.5 s
4 km/s
PTS: 1
DIF: advanced
REF: section 9.2
24. ANS:
First find the distance the station is from the epicenter using the speed and time of the S-waves.
distance = speed × time = 4 km/s × 13 s = 52 km
Next find out how long it took the P-waves to travel from the epicenter to the station.
distance
time =
speed
time =
52 km
= 8.7 s
5 km/s
Subtract the P-wave time from the S-wave time to find out how much longer it took the S-waves to reach the
station.
13 s − 8.7 s = 4.3 s
PTS: 1
DIF: advanced
REF: section 9.2
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ID: A
ESSAY
25. ANS:
During an earthquake, there is a strong burst of shaking that last for a few minutes. Foreshocks are small
bursts of shaking or tremors that may precede a large earthquake. Foreshocks can occur days to minutes
before the earthquake hits. During an earthquake, the primary waves (P-waves) arrive at the city first because
they are the fastest type of seismic waves. P-waves push and pull the rock as it moves through it. The
secondary waves (S-waves) are the next type of seismic wave to arrive at the city. These waves move slower
than P-waves. S-waves will cause the ground in the city to move in a side-to-side motion across the direction
of the traveling wave. The last wave to arrive is the surface wave. These waves occur directly at the surface
and are the slowest of the three types of waves. Surface waves can move up and down and also side-to-side,
they cause the most damage. After the earthquake aftershocks can occur that can last for hours to days after
the earthquake. Aftershocks are small tremors that follow an earthquake.
PTS: 1
DIF: advanced
REF: section 9.2
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