Chapter 11Earthquakes
Earth: An Introduction to Physical Geology, 9e
(Tarbuck/Lutgens)11.1
Multiple-Choice Questions
1)
The elastic rebound theory for the origin of earthquakes was
first proposed by ________ following the ________ earthquake.
A)
Reid; 1906, San Francisco
B)
Giuseppe; 1925, Pizza Lake
C)
Richter; 1989, Loma Prieta
D)
Mohorovicic; 1964, Anchorage
Answer:
A
Diff: 1
2)
Which one of the following statements concerning foci and
epicenters is correct?
A)
The focus is the faulted point on the surface directly above the
epicenter.
B)
The fault first cracks at the epicenter and breaks through to
the surface at the focus.
C)
The epicenter is at the surface directly above the focus where
the earthquake initiates.
D)
The earthquake starts at the focus and the rupture extends down
to the epicenter.
Answer:
C
Diff: 1
3)
Which one of the following statements is correct?
A)
P waves travel through solids; S waves do not.
B)
P and S waves travel through liquids, but P waves do not travel
through solids.
C)
S waves travel through solids and P waves travel through
liquids.
D)
P and S waves travel through liquids, but S waves do not travel
through solids.
Answer:
C
Diff: 1
4)
________ have the highest velocities.
A)
Primary waves
B)
Secondary waves
C)
Surface waves
D)
Refracted S waves
Answer:
A
Diff: 1
5)
The ________ is a direct measure of the distance from a seismic
receiving station to the focus of a distant earthquake.
A)
time interval between the first P and S- wave arrivals
B)
magnitude of the ground acceleration of surface wave passing a
receiving station
C)
time elapsed between the first P-wave arrivals from the first
and last aftershocks
D)
time interval between the first P-wave and the last surface
wave
Answer:
A
Diff: 1
6)
Which one of the following is true regarding tsunamis?
A)
They travel as deep-water waves at speeds greater than surface
seismic waves but slower than S waves.
B)
Their wave heights decrease and wavelengths increase as they
move into shallower water.
C)
They are started by fault-induced, horizontal shifts in the
seafloor that suddenly propel great masses of water in opposite
directions.
D)
They occur in the open ocean, wavelengths are many miles or
kilometers and wave heights are only a few feet.
Answer:
D
Diff: 1
7)
On a typical seismogram, ________ will show the highest
amplitudes.
A)
P waves
B)
S waves
C)
surface waves
D)
body waves
Answer:
C
Diff: 1
8)
Which of the following foundation materials is most stable
during earthquake shaking?
A)
bedrock
B)
unconsolidated moist soil
C)
water-saturate
D)
sand and mud
Answer:
A
Diff: 1
9)
The ________ magnitude scale is a measure of the energy
released. It does not directly measure the extent of building
damage.
A)
Gutenberg
B)
Reid
C)
Mercalli
D)
Richter
Answer:
D
Diff: 1
10)
Why was the Marina District, San Francisco, heavily damaged in
the 1906 and 1989 quakes?
A)
The epicenters of both quakes were right under the district.
B)
Shaking was no more extensive than elsewhere in the city, but
the whole district burned following each quake.
C)
The area is built on consolidated rock, causing the shaking to
be amplified.
D)
Liquefaction and foundation failures were common.
Answer:
D
Diff: 1
11)
Why did the 1988 Armenian earthquake (in the Armenian Republic,
then part of the former Soviet Union) result in an estimated 25,000
deaths?
A)
The buildings were constructed on unconsolidated,
water-saturated, lakebeds and foundation failures were common.
B)
Numerous, poorly constructed, top heavy, concrete slab buildings
collapsed.
C)
The quake hit at rush hour; thousands of motorists were killed
when freeways collapsed.
D)
The area was densely populated and right at the epicenter of a
magnitude 8.5 quake.
Answer:
B
Diff: 1
12)
________ is the maximum possible damage designation on the
Mercalli scale.
A)
XII
B)
12
C)
X
D)
10
Answer:
A
Diff: 1
13)
Seismic gaps are ________.
A)
unusually quiet zones along known active faults
B)
slices of land bounded by active, strike-slip faults on all
sides
C)
inactive faults cutting across high ridges and water gaps
D)
segments of active faults with creep rates of up to 2 cm/yr
Answer:
A
Diff: 1
14)
How was the Turnagain Heights area of Anchorage, Alaska, damaged
during the 1964 earthquake?
A)
It was hit by a large tsunami and then buried by a rock
avalanche.
B)
It burned in a fire set off by broken gas lines.
C)
A weak, subsurface, clay layer failed, resulting in numerous
landslides.
D)
all of the above
Answer:
C
Diff: 1
15)
Approximately how often do locked segments of the San Andreas
Fault (California) break, resulting in major earthquakes?
A)
once every six hundred years
B)
once every fifteen years
C)
once every ten thousand years
D)
once every hundred and fifty years
Answer:
D
Diff: 1
16)
would result in the largest area of ground shaking damage.
A)
shallow-focus quake along the Mississippi Valley fault zone
B)
deep-focus quake off the coast of North Africa
C)
shallow-focus quake along the San Andreas Fault
D)
very deep-focus quake beneath the Aleutian Islands
Answer:
A
Diff: 2
17)
The ________ is the point of origination for an earthquake.
A)
fault point
B)
focus
C)
seismic centroid
D)
epizone
Answer:
B
Diff: 1
18)
Approximately how much more energy is released in a 6.5 Richter
magnitude earthquake than in one with magnitude 5.5?
A)
3000 times
B)
3 times
C)
300 times
D)
30 times
Answer:
D
Diff: 1
19)
________ is a widely accepted explanation for the mechanism that
generates earthquakes.
A)
Dow's recovery theory
B)
Dupont's plastic-slip theory
C)
Richter's wave-snap theory
D)
Reid's elastic rebound theory
Answer:
D
Diff: 1
20)
P waves ________.
A)
propagate only in solids
B)
are faster than S waves and surface waves
C)
have higher amplitudes than do S waves
D)
produce the strongest ground shaking
Answer:
B
Diff: 1
21)
The Mercalli Scale is a scale from ________.
A)
1 to 12 that rates the energy required for faulting to occur
B)
1 to 10 that rates the energy released by an earthquake
C)
I to XII that rates the structural damage due to an
earthquake
D)
I to X that rates the total energy released during the main
quake and all aftershocks
Answer:
C
Diff: 1
22)
What are the smaller magnitude quakes that follow a major
earthquake?
A)
exoshocks
B)
aftershocks
C)
hyposhocks
D)
epishocks
Answer:
B
Diff: 1
23)
The largest lateral, ground displacement is produced by
________.
A)
first P arrival reflecting from the inner-outer core
boundary
B)
the S wave reflected from the core-mantle boundary
C)
horizontally vibrating surface waves
D)
vertically vibrating P waves refracted across the Moho
Answer:
C
Diff: 1
24)
The ________ is used to record ground shaking and the
earthquake-magnitude scale was invented by ________.
A)
rayoscope; Mercalli
B)
vibroscope; Rector
C)
polygraph; Freud
D)
seismograph; Richter
Answer:
D
Diff: 1
25)
The epicenter of an earthquake is the ________.
A)
point where the fault cracking initiates
B)
surface location directly above the point where the fault slip
initiates
C)
point where the minimum ground shaking is recorded
D)
point of most intense, structural damage associated with ground
shaking
Answer:
B
Diff: 1
26)
Energy is stored in rocks adjacent to the site of a future
earthquake as ________.
A)
elastic strain
B)
plastic flow energy
C)
thermal energy
D)
plastic strain
Answer:
A
Diff: 1
27)
Why was building damage so extensive in the 1985 Mexico City
quake?
A)
The epicenter was right in the city.
B)
The Richter magnitude was 8.8, and the focus was only 10 miles
from the city.
C)
Much of the city is built on filled-in, shallow lakes and
swampland.
D)
The steel frame buildings were rigid and lacked the flexibility
to withstand lateral swaying during even a moderate magnitude
quake.
Answer:
C
Diff: 1
28)
The ________ earthquake was accompanied by major damage from
tsunamis and ground failures.
A)
San Francisco, CA, 1906
B)
Loma Prieta, CA, 1989
C)
Northridge, CA, 1994
D)
Anchorage, AK, 1964
Answer:
D
Diff: 1
29)
________ was struck by three, major earthquakes during the
winter and spring months of the years 1811-1812.
A)
New Madrid, Missouri
B)
Nome, Alaska
C)
Los Angeles, California
D)
Charleston, South Carolina
Answer:
A
Diff: 1
30)
Which one of the following best characterizes tsunamis?
A)
They cause the land to ripple and oscillate.
B)
They are faster than seismic surface waves.
C)
They have relatively small amplitudes compared to their very
long wavelengths.
D)
They are easily seen at sea but are lost in the swell and
breaking waves along a coast.
Answer:
C
Diff: 1
31)
The ________ earthquake was accompanied by extensive fire
damage.
A)
Anchorage, 1964
B)
San Francisco, 1906
C)
Mexico City, 1985
D)
Yerevan, Armenia, 1988
Answer:
B
Diff: 1
32)
________ refers to the tendency for a foundation material to
lose its internal cohesion and fail mechanically during earthquake
shaking.
A)
Slurrying
B)
Liquefaction
C)
Motion slip
D)
Seismoflowage
Answer:
B
Diff: 1
33)
The ________ is directly related to the Richter
earthquake-magnitude rating.
A)
average of the highest and lowest Mercalli intensity ratings
B)
distance between the receiving station and the epicenter
C)
time interval between the first P-wave arrival and the first P
wave reflected from the crust-mantle discontinuity
D)
amplitude of the seismic waves
Answer:
D
Diff: 1
34)
Which one of the following regarding the San Andreas Fault in
California is true?
A)
a sliver of continent west of the fault is moving northward with
the Pacific plate
B)
a sliver of land west of the fault is sinking under the North
American plate
C)
continental crust east of the fault is moving east with the
North American plate
D)
the North American plate is slowly moving northward with respect
to the continental fragment west of the fault
Answer:
A
Diff: 2
11.2
Word Analysis Questions
Examine the words and/or phrases for each question below and
determine the relationship among the majority of words/phrases.
Choose the option which does not fit the pattern.
1)
A) p-waveB) s-waveC) surface waveD) body wave
Answer:
surface wave
Diff: 1
2)
A) focusB) seismographC) epicenterD) fault
Answer:
seismograph
Diff: 1
3)
A) Alaska, 1964B) San Francisco, 1906C) Mexico City, 1985D) New
Madrid, 1811-12
Answer:
New Madrid, 1811-12
Diff: 2
4)
A) tsunamiB) fireC) liquefactionD) seiche
Answer:
fire
Diff: 2
5)
Modified MercalliB) energyC) Richter D) amplitude
Answer:
Modified Mercalli
Diff: 1
11.3
True/False Questions
1)
S waves can travel through solid and liquid media.
Answer:
FALSE
Diff: 1
2)
The time between the first P-wave and S-wave arrivals is a
measure of the distance from a receiving station to the epicenter
of the earthquake.
Answer:
TRUE
Diff: 1
3)
Earthquakes result from the sudden release of elastic strain
energy previously stored in rocks surrounding a zone of fault
movement.
Answer:
TRUE
Diff: 1
4)
Reid's elastic rebound theory of earthquake generation was based
on his studies following the 1906 San Francisco earthquake.
Answer:
TRUE
Diff: 1
5)
Following a major earthquake, aftershocks diminish in magnitude
but may still be powerful enough to destroy or further damage
weakened buildings.
Answer:
TRUE
Diff: 1
6)
Horizontal vibrations, such as induced by strike-slip faulting,
are generally much more dangerous to tall buildings than vertical
up and down ground shaking.
Answer:
TRUE
Diff: 1
7)
Tsunamis are caused by sudden displacement of large volumes of
seawater.
Answer:
TRUE
Diff: 1
8)
Because their energy dissipates rapidly in deep ocean waters,
tsunamis seldom pose any danger to coastal areas far away from the
causative earthquake.
Answer:
FALSE
Diff: 1
9)
The Mercalli earthquake intensity scale uses Roman numerals from
I to XII, XII being the highest intensity.
Answer:
TRUE
Diff: 1
10)
The Richter earthquake magnitude scale is based on the total
amount of energy released by the earthquake.
Answer:
TRUE
Diff: 1
11)
The epicenter of an earthquake is on the surface of the Earth
directly above the focus.
Answer:
TRUE
Diff: 1
12)
Deep-focus earthquakes are usually very destructive because the
seismic shaking is amplified as the waves approach the surface.
Answer:
FALSE
Diff: 1
13)
Some large earthquakes are preceded by smaller magnitude
foreshocks.
Answer:
TRUE
Diff: 1
14)
In general, P- and S-wave velocities increase abruptly as the
waves pass downward across the crust-mantle boundary.
Answer:
TRUE
Diff: 1
15)
Locked fault segments experience slow creep movements, rendering
them less likely to host a large magnitude earthquake.
Answer:
FALSE
Diff: 1
16)
During the 1906 San Francisco earthquake, fire destroyed many
buildings that were otherwise undamaged or only slightly damaged by
the ground shaking.
Answer:
TRUE
Diff: 1
17)
If the P, S, and surface waves arrive almost simultaneously, the
seismic recording station is virtually at the epicenter of the
earthquake.
Answer:
TRUE
Diff: 1
18)
For shallow-focus earthquakes, surface-wave amplitudes are
usually much larger than P and S-wave amplitudes.
Answer:
TRUE
Diff: 1
19)
On earthquake distribution maps, the boundaries of the Earth's
tectonic plates are shown as zones of high seismic activity.
Answer:
TRUE
Diff: 1
20)
Unconsolidated, water-saturated soils or sediments provide good
foundation materials for buildings and other structures.
Answer:
FALSE
Diff: 1
11.4
Short Answer Questions
1)
The ________ is the site of initial rupturing associated with an
earthquake.
Answer:
focus
Diff: 1
2)
The ________ is the point on the surface directly above the site
of initial earthquake rupture.
Answer:
epicenter
Diff: 1
3)
What instrument is used to record earthquake vibrations?
Answer:
seismograph
Diff: 1
4)
A ________ is one or more smaller earthquakes that sometimes
precede a much larger, main earthquake event.
Answer:
foreshock
Diff: 1
5)
________ is the name of the earthquake-magnitude scale based on
the amount of seismic energy released during the event.
Answer:
Richter
Diff: 1
6)
What intensity scale describes the extent of structural damage
due to earthquake shaking?
Answer:
Mercalli
Diff: 1
7)
________ is another name commonly used by scientists to denote
seismic sea waves induced by earthquakes.
Answer:
Tsunami
Diff: 1
8)
________ are the first to arrive at distant receiving
stations.
Answer:
P-waves
Diff: 1
9)
An earthquake of magnitude 7.5 releases about how much more
energy than one of magnitude 5.5?
Answer:
900
Diff: 2
11.5
Critical Thinking Questions
Use complete sentences, correct spelling, and the information
presented in Chapter 11 to answer the questions below
1)
Tsunamis are only serious threats to coastal areas near an
earthquake epicenter because the waves have lost most of their
energy after moving across 100 miles of open water. Is this
statement correct? Why or why not?
Diff: 2
2)
Compare and contrast deep-focus verses shallow-focus
earthquakes. Include such things as geologic occurrence, damage
potential from ground shaking, size of areas affected by each one,
etc.
Diff: 3
3)
Would earthquakes of similar magnitudes in different regions of
the Earth cause approximately the same levels of damage
necessarily? In your explanation, consider both geologic and
human-induced factors.
Diff: 3
11.6
Visualization Questions
1)
Identify the focus and epicenter on the diagram below.
Answer:
See figure 11.2 in chapter 11 of Earth, 9e
Diff: 1
2)
Carefully study the seismogram below and note the features
labeled A through G. On the blanks provided beside each item below,
note the letter below that corresponds to that item. An S-wave a)
________
The first S-wave b) ________The first P-wave c) ________
An L-wave d) ________A surface wave e) ________
Answer:
a) C or D b) D c) G d) B or A e) B or A
Diff: 2
3)
Using the time-travel graph below, how long does it take a
P-wave to travel 2000 km? Answer:
a) four minutes
Diff: 1
4)
Study the cross section below. Which of these two identical
homes would suffer the most damage if an earthquake occurred along
the active fault?
a) ________
Explain your answer b)________
Answer:
a) home Y b) Loose sand under home Y would experience
liquefaction during a moderate or strong earthquake, so home Y
would settle down into the sand or fall over (because the sand
grains would vibrate apart in an earthquake).
Diff: 2PAGE 1