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Chapter 11 Earthquakes 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) 1
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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