Deck 10: A Violent Pulse: Earthquakes

Question 1

At any point along the surface of any nonvertical fault,as is shown in the figure below,the

A) hanging wall lies vertically above the footwall.
B) footwall lies vertically above the hanging wall.
C) hanging wall lies to the left of the footwall.
D) footwall lies to the left of the hanging wall.

Answer 1

A

Question 2

Body waves include

A) both S- and P-waves.
B) both L- and R-waves.
C) both surface and interior waves.
D) P-waves only.

Answer 2

A

Question 3

Faults that have moved recently or are likely to move in the future are referred to as ________ faults.

A) passive
B) active
C) normal
D) reverse

Answer 3

B

Question 4

The point on the Earth's surface directly above the point where an earthquake occurs is termed the

A) hypocenter (focus).
B) epicenter.
C) eye of the fault.
D) vertex.

Question 5

The intersection between a fault plane and the ground surface is called the

A) dip line.
B) plunge.
C) fault trace.
D) seismic interface.

Question 6

The point within the Earth where an earthquake originates is termed the

A) hypocenter (focus).
B) epicenter.
C) eye of the fault.
D) vertex.

Question 7

During an earthquake,if a hanging wall slides upward relative to a footwall,the fault is termed a ________ fault if the fault is shallow (much closer to horizontal than vertical).Refer to the figure below for an example of such a feature.

A) normal
B) reverse
C) strike-slip
D) thrust

Question 8

If a fault is nearly vertical in orientation and the two walls of rock on opposite sides slide past one another horizontally,the fault is termed a ________ fault.Refer to the figure below for an example of such a feature.

A) normal
B) reverse
C) strike-slip
D) thrust

Question 9

Geologists who specifically study earthquakes are called

A) seismologists.
B) paleontologists.
C) volcanologists.
D) speleologists.

Question 10

A primary force opposing motion on all faults is

A) magnetic attraction among iron-rich minerals.
B) gravity.
C) friction.
D) the van der Waals force.

Question 11

The quantity of motion that occurs along a fault is termed

A) fault gouge.
B) the fault gauge.
C) slip.
D) accumulation.

Question 12

During an earthquake,if a footwall slides upward relative to a hanging wall (as shown in the figure below),the fault is termed a ________ fault.

A) normal
B) reverse
C) strike-slip
D) thrust

Question 13

Periods of intermittent sliding on a fault because of stress release during episodes of slip,followed by stress buildup to the point that the fault is reactivated,are termed

A) chaotic faulting.
B) thrust faulting.
C) stick-slip behavior.
D) reverse faulting.

Question 14

Most earthquakes are a result of

A) a sudden change in atmospheric pressure.
B) mantle upwelling.
C) erosion.
D) lithospheric plate movement.

Question 15

Aftershocks after a major earthquake

A) may continue for days,weeks,or years after the initial earthquake.
B) are equivalent in magnitude to the original earthquake.
C) always occur on the same fault as the original earthquake.
D) typically occur only on reverse faults in subduction zones as a result of high pressures.

Question 16

Look at the figure below.Which letter corresponds to the S-wave arrival time?

A) A
B) B
C) C
D) D

Question 17

During an earthquake,if the hanging wall slides upward relative to the footwall,the fault is termed a ________ fault if the fault is steep (closer to vertical than horizontal).Refer to the figure below for an example of such a feature.

A) normal
B) reverse
C) strike-slip
D) thrust

Question 18

A __________ shows deflections traced by a seismometer,which provides a record of an earthquake.

A) seismograph
B) Mercalli
C) readout
D) shake map

Question 19

Faulting and earthquakes are examples of ________ and generally occur when rocks are relatively ________.

A) brittle deformation; cold
B) ductile deformation; cold
C) brittle deformation; hot
D) ductile deformation; hot

Question 20

Which type of fault does NOT,by definition,have a fault trace?

A) normal fault
B) reverse fault
C) blind fault
D) All faults have recognizable traces.

Question 21

Which geological setting would you NOT expect to produce a large amount of seismic activity?

A) a rift valley
B) a transform boundary
C) a collisional mountain belt
D) the interior of a tectonic plate

Question 22

Earthquake waves that travel along the Earth's surface are termed

A) interior waves.
B) S-waves.
C) surface waves.
D) body waves.

Question 23

If an earthquake's magnitude is measured based on the Richter scale,how is this abbreviated?

A) M_L
B) M_S
C) m_b
D) M_R

Question 24

An earthquake occurs with an epicenter in the town of New Madrid,Missouri,in the interior of the North American Plate.What is the most likely location of the hypocenter?

A) in New Madrid (hypocenter and epicenter mean precisely the same thing)
B) 20 km south of New Madrid
C) 20 km beneath New Madrid
D) 200 km beneath New Madrid

Question 25

Surface waves

A) travel more rapidly than body waves.
B) produce most of the damage to buildings during earthquakes.
C) are the first waves produced in an earthquake.
D) are the first waves to arrive at a seismograph station after an earthquake.

Question 26

According to the moment magnitude scale (M_w),a magnitude 8 earthquake would be 1,000 times greater than a magnitude ________ earthquake.

A) 9
B) 5
C) 7
D) 4

Question 27

Earthquakes that occur in a band called the ________ can be used to track the motion of subducted oceanic lithosphere.

A) Wegener belt
B) seismic gap
C) Wadati-Benioff zone
D) Richter zone

Question 28

Generally,which type of earthquake waves travel with the slowest velocity?

A) S-waves
B) P-waves
C) surface waves
D) All earthquake waves travel at the same speed.

Question 29

Which magnitude scale is considered the most accurate? Hint: It uses the amplitudes of several different waves,the amount of slip,and the dimensions of the slipped area on the fault.

A) the Richter scale
B) the Mercalli scale
C) the moment magnitude scale
D) the surface-wave magnitude scale

Question 30

Which of the following hazards is most likely to occur days to weeks after an earthquake?

A) fire
B) liquefaction
C) disease
D) foreshocks

Question 31

Which earthquake scale measures the amplitude of deflection of a seismograph pen,standardized to an idealized distance of 100 km between the epicenter and the seismograph?

A) the Richter scale
B) the Mercalli scale
C) the moment magnitude scale
D) the surface-wave magnitude scale

Question 32

Which earthquake severity scale varies from locality to locality for a single earthquake?

A) the Richter scale
B) the Mercalli scale
C) the moment magnitude scale
D) the surface-wave magnitude scale

Question 33

Most medium- and deep-focus earthquakes occur at

A) convergent-plate boundaries.
B) divergent-plate boundaries.
C) transform-plate boundaries.
D) hot spots.

Question 34

The vast majority of earthquakes occur

A) along transform-plate boundaries only.
B) near hot spots.
C) along passive margins.
D) along any plate boundary.

Question 35

Which type of seismic wave has the fastest velocity?

A) L-wave
B) P-wave
C) R-wave
D) S-wave

Question 36

At a minimum,how many seismic stations are necessary to locate the epicenter of an earthquake?

A) one
B) two
C) three
D) four

Question 37

As shown in the figure below,a coiled spring would be useful in illustrating any ________ wave.

A) surface
B) body
C) shear
D) compressional

Question 38

Earthquake waves that pass through the Earth's interior are termed

A) interior waves.
B) R-waves.
C) surface waves.
D) body waves.

Question 39

Wet and unconsolidated substrates are uniquely susceptible to ________ during an earthquake.

A) displacement
B) collapse
C) liquefaction
D) faulting

Question 40

Which earthquake scale is used to assess the effects of an earthquake on humans and human-made structures?

A) Richter scale
B) Mercalli scale
C) moment magnitude scale
D) surface-wave magnitude scale

Question 41

Which of the following structures is LEAST likely to survive an earthquake?

A) a brick building
B) a wood frame building
C) a building made of reinforced concrete
D) an old building that has been seismically retrofitted

Question 42

Which of the following is NOT true regarding earthquakes and destruction?

A) The bigger the earthquake,the greater the destruction will be.
B) The type of construction used will influence how damaging an earthquake can be.
C) The nature of the substrate will influence how damaging an earthquake is.
D) Seismic retrofitting can reduce the destruction caused by an earthquake.

Question 43

Seismic retrofitting is the process of

A) predicting future earthquakes.
B) strengthening existing buildings and structures.
C) mapping areas prone to earthquakes.
D) fitting earthquake data after an event to see if it should have been predicted.

Question 44

How is the Mercalli intensity scale used to determine the magnitude of an earthquake? What errors might be associated with this technique?

Question 45

Earthquake warning systems

A) are based on long-term predictions of earthquakes,allowing planners to schedule evacuations.
B) alert people just before an earthquake takes place,allowing them to evacuate buildings.
C) alert people when an earthquake has taken place,possibly giving them seconds to get to a safer place.
D) do not yet exist,but the technology is something seismologists are working on.

Question 46

Which of the following is NOT true about tsunamis?

A) They can be generated by uplift of the seafloor during an earthquake.
B) They can be generated by submarine landslides.
C) They are just as dangerous away from the coast where water depths are great.
D) They grow taller as they approach coastlines because friction slows the wave.

Question 47

Explain why tsunamis are NOT tidal waves.

Question 48

Describe two earthquake-related hazards.

Question 49

Why is an early warning system NOT considered a short-term earthquake prediction tool?

Question 50

Tsunamis are more destructive than wind-driven storm waves primarily because

A) tsunamis always have larger heights (amplitude).
B) tsunamis have longer wavelengths and thus larger volumes of water are involved.
C) the tides that cause tsunamis can be very erratic and unpredictable.
D) tsunamis also generate seismic waves that can destroy buildings.

Question 51

If you are trapped inside during an earthquake,where should you NOT be?

A) next to a large bookcase
B) under a table
C) in the center of an open room
D) in a door frame

Question 52

How is the epicenter of an earthquake different from the focus? Why are both terms useful?

Question 53

Compare and contrast P- and S-waves.

Question 54

Sketch a seismogram that has recorded an earthquake.Be sure to label the arrival of each of the three types of seismic waves and include at least one aftershock.

Question 55

Where do earthquakes occur? Please explain your answer in the context of plate tectonics.Are there exceptions?

Question 56

Which of the following is NOT true concerning the long-term predictions of earthquakes?

A) They are based on past earthquake activity.
B) They work on the principle that zones of past seismicity will be active in the future.
C) They include the notion of seismic gaps-places where an earthquake is overdue.
D) They allow city planners to schedule evacuations up to a year in advance.

Question 57

Short-term predictions of earthquake behavior

A) have saved millions of lives in the past decade alone.
B) have been largely unreliable.
C) are primarily based on the behavior patterns of farm animals.
D) are correct approximately 50% of the time.

Question 58

Why do deep-focus earthquakes occur along convergent plate boundaries? Why are they absent along divergent or transform boundaries?

Question 59

A tsunami is

A) a seawave generated by an earthquake,landslide,or submarine volcanic eruption that may destroy coastal cities thousands of kilometers from its source.
B) a sloshing of water back and forth within a lake or a bay.
C) a wave caused by unusually large tidal forces.
D) the tendency of wet,clay-rich soils to behave like a liquid during an earthquake.

Question 60

Why is an empty field the safest place to be in an earthquake?