Deck 8: A Violent Pulse: Earthquakes

Question 1

Faulting and earthquakes are examples of what type of deformation?

A) brittle
B) elastic
C) ductile
D) fluid

Answer 1

A

Question 2

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 2

A

Question 3

The displacement that occurs during the largest earthquakes can be as long as

A) several millimeters.
B) several centimeters.
C) several meters.
D) several kilometers.

Answer 3

C

Question 4

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 5

Geologists who specifically study earthquakes are called

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

Question 6

During an earthquake,if a hanging wall slides downward relative to a footwall,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 7

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 8

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

Question 9

A ____________ is a scientific instrument used to record the ground motions produced by an earthquake.

A) seismic wave
B) seismometer
C) tidal gauge
D) strain gauge

Question 10

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 11

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 12

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 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

Before an earthquake,rocks can respond to applied stress to a small degree by bending and warping without breaking.This is termed _________.

A) elastic behavior
B) faulting
C) seismic velocity
D) brittle deformation

Question 15

Faults occur in many locations,but most faults had displacement in the distant past and are unlikely to move again in the future.This means that most faults are

A) active faults.
B) thrust faults.
C) inactive faults.
D) submarine faults.

Question 16

The energy that is released during an earthquake travels through the Earth as vibrations termed _______.

A) gravity waves
B) tsunamis
C) seismic waves
D) sound waves

Question 17

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 18

The quantity of motion that occurs along a fault is termed

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

Question 19

Most earthquakes are a result of

A) a sudden change in atmospheric pressure.
B) mantle upwelling.
C) erosion of bedrock.
D) movement of rocks along faults.

Question 20

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 21

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

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

Question 22

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 23

Which geological setting is likely to experience the least 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 24

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 25

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

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

Question 26

Generally,which of the following types 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 27

Which type of seismic wave has the fastest velocity?

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

Question 28

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

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

Question 29

Most medium- and deep-focus earthquakes occur at

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

Question 30

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 31

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 32

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.

Question 33

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

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

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

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

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

Question 36

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 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

A long delay between the arrival of P-waves and S-waves at a seismometer means that

A) the earthquake only produced P-waves.
B) the focus of the earthquake was very deep in the Earth's crust.
C) the seismometer is located far from the earthquake.
D) the earthquake had a very small displacement.

Question 39

On average,there are _______occurrences of light and minor earthquakes compared to the number of major and great earthquakes each year.

A) many thousands more
B) approximately ten times as many
C) about the same number of
D) many fewer

Question 40

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 41

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

Question 42

Describe two earthquake-related hazards.

Question 43

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

Question 44

Designing and retrofitting building to withstand the effects of earthquakes is a type of

A) earthquake zoning.
B) earthquake engineering.
C) seismic hazard mapping.
D) seismic retrofitting.

Question 45

Determining where roads and building should be built based on where land is stable and less prone to landslide or liquefaction during an earthquake is an example of ________.

A) earthquake zoning
B) earthquake engineering
C) seismic hazard mapping
D) seismic retrofitting

Question 46

What is an early earthquake warning system,and why does this differ from a short-term earthquake prediction tool?

Question 47

The average length of time between earthquakes along a fault is termed the ______.

A) elastic strain
B) S-P time
C) seismic gap
D) recurrence interval

Question 48

Short-term predictions of earthquake behavior have

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

Question 49

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 50

Explain why "tidal wave" is actually a poor term for tsunamis.

Question 51

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

Question 52

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 53

Sketch a seismogram that has recorded an earthquake.Be sure to label the arrival of each of the three main types of seismic waves (P-waves,S-waves,and surface waves).

Question 54

What kind of information is shown on a seismic hazard map?

A) the probability that different regions will experience a large earthquake
B) the likely magnitude of future earthquakes in different regions
C) the distribution of small and large earthquakes in different regions
D) the locations of large earthquakes in the past

Question 55

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

Question 56

Earthquake early 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 57

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 58

Why is an empty field a very safe place to be in an earthquake?

Question 59

Compare and contrast P- and S-waves.

Question 60

Tsunamis are most commonly generated by sudden _________ movement of the seafloor during an earthquake.

A) strike-slip
B) horizontal
C) vertical
D) circular