Deck 10: Earthquakes

Question 1

Major earthquakes are likely in all of the following tectonic settings EXCEPT:

A) divergent boundaries.
B) subduction zones.
C) continental collision boundaries.
D) transform boundaries.

Answer 1

A

Question 2

Few earthquakes are recorded at depths below 450 miles because:

A) they are too deep within the Earth to be detected by seismographs.
B) brittle failure does not occur at depths below 200 miles.
C) slabs that descend that far have been heated sufficiently to deform plastically.
D) lithostatic pressure at these depths prevents rocks from shifting relative to each other.

Answer 2

C

Question 3

All of the following are true of tsunami EXCEPT:

A) they are often responsible for the destruction of ships at sea.
B) they can travel at speeds greater than 500 miles per hour.
C) they can often form waves more than 100 feet high.
D) they are caused by undersea earthquakes.

Answer 3

A

Question 4

When rocks break or a fault moves, energy is released in the form of:

A) water waves.
B) sound waves.
C) light waves.
D) seismic waves.

Question 5

If an earthquake occurs, the first waves to arrive at a seismograph are the:

A) P waves.
B) side- to- side surface waves.
C) S waves.
D) rolling surface waves.

Question 6

In the formula for determining the seismic moment of an earthquake, the quantity measured for "strength of rock" is:

A) the brittle failure modulus.
B) the deformation modulus.
C) the plastic modulus.
D) the elastic modulus.

Question 7

The lag between P- and S- wave arrival times can be converted to:

A) the seismic moment of the earthquake.
B) the intensity of the earthquake.
C) the distance between the earthquake epicenter and the seismograph station.
D) the magnitude of the earthquake.

Question 8

Earthquakes measuring 5 and 7 on the Richter scale differ in wave amplitude by:

A) 2 times.
B) 10 times.
C) 100 times.
D) 1000 times.

Question 9

All of the following represent clues to the cause of a 2- meter high tsunami that struck Japan in 1700 EXCEPT:

A) native American legends describe a quake and tsunami in the Pacific Northwest.
B) large areas of drowned trees in the Pacific Northwest are covered with a thin sand layer.
C) tree ring records from roots indicate temporary submergence of trees between 1699 and 1700.
D) seismic records at that time indicate a massive quake in the Seattle area.

Question 10

The type of earthquake waves that have been known to produce symptoms of seasickness are:

A) rolling surface waves.
B) P waves.
C) side- to- side surface waves.
D) S waves.

Question 11

Japan is the site of about 15% of the Earth's seismic energy release because it is located:

A) where the Pacific plate descends beneath the Eurasian plate.
B) at the transform boundary between the Pacific and Eurasian plates.
C) where the Eurasian plate descends beneath the Pacific plate.
D) at the continental collision boundary between the Eurasian and Pacific plates.

Question 12

The Mercalli intensity scale is ineffective in providing information about all of the following earthquake effects EXCEPT:

A) characterization of historical earthquakes.
B) utilitization in uninhabited parts of the world.
C) location of the earthquake epicenter.
D) determination of damage due to actual ground motion.

Question 13

The ability to fight earthquake- caused fires is commonly hampered by:

A) tinder- dry structures that readily burn.
B) narrow streets that impede passage of fire- fighting equipment.
C) broken water mains that lose pressure.
D) all of the above.

Question 14

Ground displacement during the 1906 San Francisco earthquake was:

A) 15 feet laterally.
B) 25 feet laterally.
C) 39 feet vertically upward.
D) 53 feet vertically downward.

Question 15

Which of the following terms is NOT described correctly?

A) A seismogram is a visual record of seismic waves and their amplitudes.
B) A seismograph is an instrument that measures the magnitude of an earthquake.
C) A seismometer is the scale used for measuring seismic waves.
D) A seismic wave is the way earthquake energy is transmitted through the Earth.

Question 16

The magnitude of most of the Earth's earthquakes is from on the Richter scale.

A) 1.0 to 2.0
B) 2.0 to 3.0
C) 3.0 to 3.9
D) 4.0 to 4.9

Question 17

Most earthquakes are caused by:

A) the release of accumulated strain energy in rocks undergoing elastic deformation.
B) magma moving forcefully through underground caverns.
C) the release of accumulated strain energy in rocks undergoing plastic deformation.
D) excess lithostatic pressure on rocks buried deep within the Earth.

Question 18

Which of the following statements about earthquakes is NOT true?

A) An earthquake's focus is the place within the Earth where rocks shift in response to stress.
B) Aftershocks are caused by continued reverberation of rock after a major earthquake.
C) After an earthquake, rocks along a fault temporarily lock in place and resist further movement, causing earthquakes to be sporadic rather than continuous.
D) An earthquake's epicenter is in the exact center of the fault that causes the earthquake.

Question 19

All of the following are damaging effects of earthquakes EXCEPT:

A) vertical ground displacement along dip- slip faults.
B) landslides involving unstable rock, rock fragments, or soil.
C) liquefaction, the release of flood waters by the destruction of a dam.
D) displacement of fences through ground shifts in which a block of earth moves laterally.

Question 20

Which of the following statements about earthquake depths and magnitudes is NOT true?

A) Because rocks buried deep in the Earth cannot store strain energy very well, many earthquakes occur in rocks more than 435 miles below the Earth's surface.
B) Earthquakes occurring at depths between 45 and 180 miles are considered intermediate in depth.
C) Most major earthquakes occur at depths of less than 60 miles.
D) Most minor earthquakes occur at a depth of less than 60 miles.

Question 21

Which of the following statements concerning moonquakes is NOT true?

A) Many are caused by meteorite impacts.
B) Most have a magnitude between 2.5 to 5.0.
C) Some are caused by the gravitational pull of the Earth.
D) Only about 3000 moonquakes are recorded each year, in comparison to the million or more quakes that occur on the Earth.

Question 22

All of the following are known to have been human causes of earthquakes EXCEPT:

A) draining of wetlands, because of the removal of lubricating fluids from shallow faults.
B) the injection of liquid waste into bedrock, because of the added lubrication to deep faults.
C) man- made reservoirs, because of the extreme weight of the water.
D) man- made reservoirs, because of water seeping into and lubricating fractured bedrock.

Question 23

All of the following are true of intraplate earthquakes EXCEPT:

A) they occur in extremely brittle rocks, and their effects are often felt over a wider area than those of plate boundary earthquakes.
B) they occur in areas of the Earth's crust that are already weakened by numerous faults.
C) they almost always occur at the surface, and are readily observable.
D) they are generally shallow, with a focus less than 30 miles deep.

Question 24

San Francisco is the site of numerous earthquakes because it is located:

A) at the transform boundary between the Pacific and North American plates.
B) in a rift zone between the North American and Pacific plates.
C) where the Pacific plate descends beneath the North American plate.
D) where the North American plate descends beneath the Pacific plate.

Question 25

In an earthquake- prone region, the safest house would be a:

A) log cabin built on loose soil.
B) log cabin built on bedrock.
C) brick house built on bedrock.
D) brick house built on loose soil.

Question 26

Which of the following is NOT true of earthquake waves?

A) Surface waves arrive at a seismograph first because they are not impeded by rock.
B) S waves are body waves and act on rocks in a shearing motion.
C) P waves are body waves and act by compressing and expanding rocks.
D) The combining of both types of surface waves is responsible for most earthquake damage to rigid structures.

Question 27

A seismograph works:

A) with the aid of electrodes inserted in the Earth to detect fluctuations in electrical conductivity caused by vibrations.
B) via a stationary satellite that is aimed at a specific point on the Earth's surface to detect the slightest tremors.
C) by triggering a spring- loaded mechanism during an earthquake.
D) by means of a freely suspended weight that tends to remain stationary when the Earth vibrates.

Question 28

The magnitude of the 1700 Northwest earthquake was probably:

A) 8.0.
B) 8.5.
C) 9.0.
D) 9.5.

Question 29

All of the following hypotheses have been proposed to explain intraplate earthquakes EXCEPT:

A) plate motion stresses the weakened and faulted crust at some intraplate sites.
B) mid- continent sediment deposition weighs down the crust, producing pressure that reactivates its faults.
C) substantial quantities of meltwater from the most geologically recent ice age has infiltrated and saturated networks of subsurface fractures.
D) long- term erosion has removed vast quantities of surface materials, allowing the buoyant crust to rise and generate stress on old faults.

Question 30

Blind faults are:

A) smaller faults that are part of a larger fault network.
B) faults with little or no surface expression.
C) faults that do not shift unless triggered by an adjacent, more active fault.
D) faults that lie below other faults.

Question 31

All of the following statements describe the seismograph patterns of earthquakes monitored by the International Data Center EXCEPT:

A) energy waves begin slowly.
B) all energy waves are generated instantaneously.
C) energy waves peak erratically.
D) energy waves decrease unevenly.

Question 32

An earthquake- induced seiche can best be described as:

A) an extended period of wave activity on a lake.
B) a back- and- forth region of waves on a lake.
C) a lake- sized tsunami.
D) a back- and- forth motion of the entire body of water within a lake.

Question 33

The magnitude of the powerful New Madrid, Missouri earthquake event of early 1812 may have exceeded:

A) 8.0.
B) 5.0.
C) 7.0.
D) 6.0.

Question 34

Which of the following statements concerning liquefaction is NOT true?

A) It is caused when a substantial quantity of groundwater is forced into unconsolidated sediment.
B) Water pressure between sediment grains removes frictional contact between them.
C) Previously cohesive sediment is caused to flow like a slurry of mud.
D) Liquefaction can cause virtual geysers of sand.

Question 35

Earthquake waves that alternately cause rocks to compress and dilate are:

A) S waves.
B) rolling surface waves.
C) side- to- side surface waves.
D) P waves.

Question 36

All of the following practices would tend to minimize the amount of damage sustained by a particular building during an earthquake EXCEPT:

A) joining structural elements (floors, walls, ceilings) firmly rather than loosely.
B) locating the building as far as possible from an active fault.
C) using wood instead of concrete block as the building material.
D) building on unconsolidated sediment rather than on bedrock.

Question 37

Critical facilities that must survive an earthquake to prevent a heavy toll of human life include:

A) nuclear power plants.
B) fire and police departments.
C) large dams.
D) all of the above.

Question 38

Very minor earthquakes (2.0-3.0 on the Richter scale) occur on an average of 1000 per day. Earthquakes of magnitude 7.0-7.9 have an annual average occurrence of:

A) 8 per year.
B) 18 per year.
C) 128 per year.
D) 180 per year.

Question 39

To locate the epicenter of an earthquake, a seismologist must determine all of the following EXCEPT:

A) the distance from the epicenter to at least three different seismological stations.
B) the difference in travel times between P waves and S waves.
C) the velocity of both P waves and S waves.
D) the depth of the earthquake and the type of fault from which it originated.

Question 40

Preliminary estimates of earthquake magnitude based on seismic tracings generally differ from values obtained by thorough analysis of seismic moment:

A) very little.
B) The two scales bear no relationship.
C) substantially.
D) by at least one full point on the Richter scale.

Question 41

One method suggested to control or prevent major damaging earthquakes is to:

A) glue or cement the two sides of a fault in place to prevent further movement along the fault.
B) control the amount of lubricating fluids between the two sides of major faults.
C) induce numerous smaller earthquakes to relieve strain energy that would cause a major earthquake.
D) reduce the rate of tectonic plate movement.

Question 42

Describe the fundamental principle by which a seismograph works.

Question 43

When Benioff- Wadati zones are plotted on a map, they show:

A) semiconcentric zones of varying degrees of earthquake damage.
B) elastic modulus values in rocks within a subduction zone.
C) earthquake numbers decreasing away from areas of oceanic rifting.
D) earthquake foci becoming progressively deeper inland from ocean trenches.

Question 44

All of the following are differences between the Richter scale and the Mercalli intensity scale EXCEPT:

A) the Richter scale uses quantitative data, whereas the Mercalli scale uses qualitative data.
B) the Richter magnitude decreases as distance from the epicenter increases, while the Mercalli measurement remains the same regardless of distance.
C) the Richter scale measures the size of earthquake waves, whereas the Mercalli scale measures the amount of damage.
D) the Richter scale is logarithmic, while the Mercalli scale is linear.

Question 45

List and briefly describe four of the damaging effects of earthquakes.

Question 46

Describe the various kinds of seismic waves.

Question 47

Liquefaction during an earthquake primarily affects:

A) foliated metamorphic rocks.
B) rock fragments detached from bedrock.
C) thick sedimentary rock layers.
D) fine- grained clays and silts.

Question 48

The Richter scale measures which characteristic of earthquakes?

A) Preliminary magnitude from seismographic trace.
B) Observed destructiveness or intensity.
C) The total energy or seismic moment.
D) The amount of energy released or magnitude.

Question 49

What causes earthquakes?

Question 50

What methods are used for short- term prediction of earthquakes?

Question 51

What do we know about moonquakes?

Question 52

What factors determine whether a particular building is susceptible to damage by an earthquake?

Question 53

Describe three of the theories that attempt to explain the cause of intraplate earthquakes.

Question 54

What are some of the benefits of seismograph station networks?

Question 55

Explain why the Mercalli intensity scale does not measure earthquakes objectively.