Deck 10: Earthquakes and Earth's Interior

Question 1

________ is the 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 1

D

Question 2

________ have the highest velocities.

A)Primary waves
B)Secondary waves
C)Surface waves
D)Diffracted S waves

Answer 2

A

Question 3

Which one the following does not propagate through liquids?

A)seismic sea waves
B)S waves
C)P waves
D)converted inner core waves

Answer 3

B

Question 4

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.

Question 5

What are the two fundamentally different types of seismic waves?

A)body waves and surface waves
B)P waves and S waves
C)seismic earth waves and seismic sea waves (tsunamis)
D)tidal waves and breaking waves

Question 6

Energy is stored in rocks adjacent to the site of a future earthquake as ________.

A)elastic stress
B)ballistic shock waves
C)thermal vibrations
D)plastic strain

Question 7

The largest lateral, ground displacement experienced at any location 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 crust-mantle boundary

Question 8

How does a seismograph detect vibrations from the passing wave front of an earthquake?

A)The whole instrument moves up and down (or back and forth)on the ground, so that it starts jiggling a little weight inside that trips the detector to record the earthquake.
B)The instrument is anchored to the ground or buried in a vault so that it is stationary with respect to the earth.When the instrument moves, the suspended mass inside is relatively stationary due to inertia.The relative motion registers the quake.
C)The instrument vibrates with the ground as it rolls along a track above the hyypocentre.
D)The wave front seeks out the instrument which stops vibrating when the wave front reaches it.

Question 9

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

Question 10

What happens inside a rock as a wave front from a P wave passes through?

A)The little parcel of rock rotates about its own location in an ellipse until the wave passes.
B)The little parcel of rock shimmies from side to side as the wave passes, with the greatest motion at the Earth's surface, dying out with depth.
C)The volume of the rock stays fixed, but it shears back and forth, distorting the rock's internal shape as the wave passes through.
D)The rock moves toward and away from the earthquake as the volume of the material alternately expands and contracts, changing the rock's density while the compression-rarefaction wave passes through.

Question 11

The ________ is the point of origination for an earthquake.

A)fault plane
B)hypocentre
C)seismic belly button
D)epizone

Question 12

What are the smaller magnitude quakes that follow a major earthquake?

A)aftershocks
B)airshocks
C)hyposhocks
D)epishocks

Question 13

On a typical seismogram, ________ will show the highest amplitudes.

A)P waves
B)S waves
C)surface waves
D)body waves

Question 14

Which one of the following statements concerning P waves is true?

A)They are not transmitted through the outer and inner cores.
B)They arrive first at distant receiving stations.
C)They are not refracted across the crust-mantle boundary.
D)They propagate by vibrations at right angles to the ray path.

Question 15

Most large earthquakes result from ________.

A)impacts of meteorites from outer space
B)explosions and detonations of military ordnance especially of nuclear weapons
C)storm waves and tsunamis crashing onto the shoreline so hard that the earth shakes
D)the wavelike vibration of the Earth in response to the rapid release of stored elastic energy in deformed rocks

Question 16

What happens inside a rock as a wave front from an S wave passes through?

A)The little parcel of rock rotates about its own location in an ellipse until the wave passes.
B)The little parcel of rock shimmies from side to side as the wave passes, with the greatest motion at the Earth's surface, dying out with depth.
C)The volume of the rock stays fixed, but it shears back and forth, distorting the rock's internal shape as the wave passes through.
D)The rock moves toward and away from the earthquake as the volume of the material alternately expands and contracts, changing the rock's density while the compression-rarefaction wave passes through.

Question 17

Which is the correct relationship for the relative velocities of the different types of seismic waves?

A)P = 1.7 X S and L = 0.9 X S
B)L X 0.9 = S = P X 1.7
C)P X 0.9 = L X 1.7 = S
D)S = 1.7P and S = 0.9 X L

Question 18

Which one of the following statements concerning hypocentres and epicentres is correct?

A)The hypocentre is the faulted point on the surface directly above the epicentre.
B)The fault first cracks at the epicentre and breaks through to the surface at the hypocentre.
C)The epicentre is at the surface directly above the hypocentre where the earthquake initiates.
D)The earthquake starts at the hypocentre and the rupture extends down to the epicentre.

Question 19

The most damaging type of earthquake wave for buildings and engineering structures on top of the ground is a surface wave with horizontal motion back and forth parallel to the passing wave front.Which description fits this type of surface wave?

A)The little parcel of rock rotates about its own location in an ellipse until the wave passes.
B)The little parcel of rock shimmies from side to side as the wave passes, with the greatest motion at the Earth's surface, dying out with depth.
C)The volume of the rock stays fixed, but it shears back and forth, distorting the rock's internal shape as the wave passes through.
D)The rock moves toward and away from the earthquake as the volume of the material alternately expands and contracts, changing the rock's density while the compression-rarefaction wave passes through.

Question 20

________ formulated the elastic rebound theory after the ________ earthquake.

A)Gutenberg; Anchorage, 1964
B)Churchill; northern India, 1896
C)Richter; Loma Prieta, 1989
D)Reid; San Francisco, 1906

Question 21

The ________ is a direct measure of the distance from a seismic station to the hypocentre 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 station
C)time elapsed between the first P-wave arrivals from the first and last aftershocks
D)how long before the earthquake your animals started acting agitated

Question 22

Approximately how much more energy is released in a 6.5 Richter magnitude earthquake than in one with magnitude 5.5?

A)3200 times
B)100 times
C)32 times
D)10 times

Question 23

The ________ magnitude scale is a measure of the energy released as judged from the amplitude of the largest seismic wave.It does not directly measure the extent of building damage.

A)modified Mercalli
B)moment magnitude
C)open-ended Richter
D)shaklee natural

Question 24

________ is the maximum possible damage designation on the Mercalli scale.

A)XII
B)12
C)X
D)10

Question 25

How can the exact distance to an earthquake be determined if you only have a single seismic station to record it?

A)by measuring the P-wave arrival time and its intensity and using a formula
B)by measuring the duration of the surface wave train
C)by measuring the difference between the P and S arrival times and using a travel time curve for arrival versus distance
D)You dig up your seismograph and take it to a destitute seismologist and offer to trade the instrument for the answer to your question!

Question 26

Which is not a criterion for determining an earthquake's Mercalli intensity?

A)amplitude of the maximum seismic wave
B)damage done to buildings
C)descriptions of the event
D)secondary effects like ground rupture or landslides

Question 27

What was the largest Richter magnitude ever recorded for an earthquake?

A)2)0
B)5)4
C)8)9
D)10.0

Question 28

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

Question 29

What is the average P-wave velocity (km/sec)if the seismic station is 2000 km from the epicentre?

A)8)33
B)500
C)200
D)4)66

Question 30

The ________ is directly related to the Richter earthquake-magnitude rating.

A)average of the highest and lowest Mercalli intensity ratings
B)distance between the seismic station and the epicentre
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

Question 31

The ________ is used to record ground shaking and the earthquake-magnitude scale based on the largest seismic wave motion was invented by ________.

A)Chinese ball juggler, Lao Tzu
B)vibrator; Dr.Ruth
C)polygraph; Freud
D)seismograph; Richter

Question 32

What is the average S-wave velocity (km/sec)if the seismic station is 2000 km from the epicentre?

A)4)38
B)263
C)43.8
D)4)66

Question 33

Why are the travel-time curves for the P-wave and S-wave arrivals curved and not straight lines?

A)The greater the distance, the deeper the P and S waves travel, refracting through progressively denser layers.
B)During an earthquake, Earth shakes so much that it is like a quivering rubber ball and all of the distances are wrong.
C)They should be straight lines.Earth is flat and the time-travel graph proves it!
D)They have to bend with the curvature of the Earth.

Question 34

When, and on what fault, was Canada's greatest earthquake, for which we have a seismic record?

A)magnitude 9.0, January 26, 1700, Cascadia Subduction Zone
B)magnitude 5.9, November 25, 1988, Grenville Fault
C)magnitude 7.6, February 28, 2001, Cascadia Subduction Zone
D)magnitude 8.1, August 22, 1949, Queen Charlotte Fault

Question 35

What was the smallest Richter magnitude that can be felt by a human?

A)0)5
B)1)0
C)2)0
D)4)0

Question 36

If an earthquake occurred 2000 km away from a seismic station, how long after the earthquake would the station detect the P-wave arrival?

A)4 minutes
B)2 minutes
C)7)5 minutes
D)2000 minutes

Question 37

Along which path is the distance to the epicentre measured?

A)the distance around the outside circumference of the Earth between your station and the epicentre following a great circle route (like a line of longitude)
B)the shortest distance through the Earth between the earthquake and your station (like the chord across a circle)
C)the shortest great circle route that passes through the north pole
D)the longest great circle route that passes through your station

Question 38

The epicentre 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 costly structural damage associated with ground shaking

Question 39

If an earthquake occurred 2000 km away from a seismic station, how long after the P-wave arrival would the station detect the S-wave arrival on the same seismogram?

A)3)6 minutes
B)2 minutes
C)4 minutes
D)7)6 minutes

Question 40

If the S-wave arrival time was 4 minutes later than the P-wave arrival time for a distant earthquake on the same seismogram, what was the distance from the seismic station to the epicentre?

A)2450 kilometres
B)950 kilometres
C)2000 kilometres
D)2150 kilometres

Question 41

Which of the following foundation materials is most stable during earthquake shaking?

A)bedrock
B)unconsolidated moist soil
C)water-saturated sand
D)sand and mud

Question 42

Which of the following statements is true?

A)The seafloor undergoes sudden horizontal slippage during an earthquake, causing the overlying water to be accelerated or pushed laterally, initiating a tsunami.
B)The seafloor suddenly moves upward or downward during an earthquake, displacing the sea surface into a mound or trough, as gravity tries to restore the sea surface a very fast tsunami wave is generated.
C)As seafloor is subducted, water is squeezed out of deep sea sediment to produce a surface wave (tsunami).
D)Tsunami can be generated by sea cliffs tumbling into tidewater, thereby generating a surface wave.

Question 43

The ________ earthquake was accompanied by major damage from tsunamis and ground failures.

A)San Francisco, 1906
B)Loma Prieta, 1989
C)Northridge, 1994
D)Anchorage, 1964

Question 44

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 rotational landslides.
D)Rioting by frenzied inhabitants in Anchorage's worst slum area.

Question 45

Which one of the following is true regarding tsunamis?

A)They travel as deep-water waves at speeds greater than the speed of sound in water so they hit the coast followed by a massive rumble like a sonic boom.
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 sea floor that suddenly propel great masses of water upwards like spreading ripples in all directions.
D)They occur in the open ocean like fast surface waves travelling at hundreds of kilometres per hour, wavelengths are hundreds of kilometres, and wave heights < a metre.

Question 46

What instrumentation permits the "Tsunami Warning System" to assess the possibility of a tsunami and decide when to raise the coastal alert?

A)tilt meters on the island of Oahu
B)networked seismographs, tide gauges, and sea buoys around the Pacific Basin all telemetred to the centre in Hawaii
C)GPS satellites that monitor the sea surface height to +/- 5 centimetre accuracy
D)a trip wire attached to a rubber ducky in the middle of the Pacific

Question 47

In collecting historic and geologic data on the geographic extent of rupture zones for great earthquakes ________.

A)individual rupture zones tend to occur adjacent to one another, without appreciable overlap, tracing out the plate boundary
B)a clear pattern is bound to emerge eventually, if only we wait long enough
C)zones of rupture for a singe great earthquake string out along the fault intermittently with intact regions like tears on a dotted line
D)zones of rupture tend to be the same size and are sequentially located along the entire length of the fault, clearly indicating exactly which area is the next to break

Question 48

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.

Question 49

What causes mud and sand volcanoes or geysers in a modern delta or low tide beach setting?

A)gas venting from underlying hydrocarbon deposits
B)liquefaction, dewatering, and compaction of water saturated materials at depth often caused by seismic shaking or loading changes
C)new volcanic activity boiling the water beneath the edge of the sea
D)meteorite impacts during solar flares

Question 50

Why was building damage so extensive in the 1985 Mexico City quake?

A)The epicentre was right in the city.
B)The Richter magnitude was 8.8, and the focus was only 25 kilometres from the city.
C)Much of the city is built on lake silts and former swampland that vibrated with the same 2 second period as, and amplified the incoming surface waves.
D)The steel frame buildings were rigid and lacked the flexibility to withstand lateral swaying during even a moderate magnitude quake.

Question 51

Seismic gaps are ________.

A)unusually quiet zones, which have not produced earthquakes, along known active faults
B)sweatshirt boutiques located in Vancouver
C)inactive faults cutting across high ridges and water gaps
D)segments of active faults with creep rates of up to 2 centimetres/year

Question 52

The ________ magnitude scale, better for the largest earthquakes, is a measure of the energy released as judged from the displacement on the fault, its surface area and the rock's shear strength.It can also be calculated from very long period seismograms.

A)modified Mercalli
B)moment magnitude
C)open ended Richter
D)Pinochet

Question 53

How is Moment Magnitude (MW )calculated?

A)from surface wave magnitude measured one minute after the first P-wave arrival
B)from the amount of building or other infrastructure damage in large earthquakes with more than one minute of of ground shaking
C)from average fault displacement, average fault rupture area, and rock shear strength in the fault zone or by measuring very long period waves on special long period seismometers, triggered to record only very large earthquakes
D)from S-wave magnitude measured one minute before the last P-wave arrival

Question 54

What is the ML calculated for a local earthquake with an S-P arrival difference of 2.0 sec and maximum S-wave amplitude of 1 mm?

A)1)5
B)1)0
C)2)0
D)4)0

Question 55

The geologic term, ________, denotes phenomena that precede an earthquake and might be used to give advance warning.

A)creepy feelings
B)precursor
C)premonition
D)prescience

Question 56

The ________ earthquake was accompanied by extensive fire damage.

A)Anchorage, 1964
B)San Francisco, 1906
C)Mexico City, 1985
D)Haiti, 2010

Question 57

Which of the following statements is true?

A)Tsunamis are only serious threats to low lying coastal areas near an earthquake epicentre because the waves have lost most of their energy after moving across 100 kilometres of open water.
B)Tsunamis lose little of their energy moving long distances through open water, so they can present serious threats to low lying coastal areas, even thousands of kilometres from the location of the initiating earthquake or submarine landslide.
C)Tsunamis only travel short distances so coastal areas have to be close to the epicentre to be in any real danger.
D)Tsunamis stop when they reach a shoreline so people are safe as long as they stay inland.

Question 58

What amplitude would a ML6.0 earthquake with a 50 sec S-P arrival difference show on a seismogram?

A)20 millimetres
B)5 millimetres
C)10 millimetres
D)50 millimetres

Question 59

Which buildings fare the worst, close to the epicentre of large earthquakes?

A)single storey stick-woodframe houses (like the second Little Pig)
B)3-4 storey woodframe "walk-up" apartments
C)unreinforced masonry buildings (Like the third Little Pig's brick or stone house)
D)high rise office towers and many storey apartments

Question 60

________ refers to the tendency for a foundation material to lose its internal cohesion and fail mechanically during earthquake shaking.

A)Slurrying
B)Liquefaction
C)Ooey-gooefication
D)Seismoflowage

Question 61

The ________ is the seismic discontinuity that forms the boundary between the crust and mantle.

A)Mojo
B)Moto
C)Mono
D)Moho

Question 62

What acoustic phenomenon causes the shadow zone for P-wave arrivals at epicentral angles between 100° and 140°?

A)attenuation
B)dispersion
C)reflection
D)refraction

Question 63

A shallow-focus, large earthquake occurs directly under the South Pole.A seismic station at the North Pole would receive ________.

A)S waves from this quake but not P waves
B)both P waves and S waves from this quake separated in arrival times by two minutes
C)neither P waves nor S waves from the quake
D)P waves from this quake but no S waves would be detected

Question 64

The precise radius of the inner core was not measured until relatively recently.How was this accomplished?

A)by finding the S-wave shadow zone beyond 105°
B)by Neil Armstrong conducting hammer seismic experiments during a 1960's Apollo Mission
C)by using a precisely known, underground nuclear weapons test in the Nevada desert in the early 1960s
D)by measuring the edge of the P-wave shadow zone from the great Chilean earthquake of 1960

Question 65

Which of the following best characterizes how the diameter of Earth's core and the nature of the outer core were discovered?

A)Crystalline iron was found in lavas erupted from the deepest known hot spots.
B)by analysis of the P-wave and S-wave shadow zones
C)because P-wave speeds are higher in the outer core than in the lower mantle
D)by using the ratio of iron meteorites to stony meteorites to deduce the relative diameters of the core and mantle

Question 66

The ________ of the Earth does not transmit S waves.

A)outer mantle
B)inner crust
C)outer core
D)deep mantle

Question 67

What causes the shadow zone for no S-wave arrivals beyond epicentral angles of 100°?

A)The Earth is hollow.
B)The liquid outer core will not pass shear waves, so any down-going shear wave energy is converted to additional "late" P waves at the mantle-core boundary.
C)All shear waves are converted to surface waves at the mantle-core boundary.
D)All seismographs are located on the near side of the earth.

Question 68

________ discovered the crust-mantle seismic discontinuity in ________, proving that the Earth was not internally homogeneous but layered.

A)Beno Gutenberg; 1914
B)Arne Sachnussen, 1885
C)Charles Richter; 1935
D)Andrija Mohorovicic; 1909

Question 69

What is the main contribution of Canada's Lithoprobe Project?

A)discovering Canada's richest mineral deposits at the base of the crust
B)drilling deep holes to probe the Canadian lithosphere and explore for hydrocarbons along the way
C)multichannel reflection seismic profiling of the entire crustal architecture, to the base of the lithosphere
D)radiometric dating of the oldest rocks laid down at the base of the lithosphere

Question 70

What does a P wave do to the rock it passes through?

A)It lifts it up and down in a wavelike motion (perpendicular to the advancing wave front), distorting the rock's shape while holding its volume (and density)constant.
B)It alternately compresses and expands the rock (like the bellows of an accordion)along the direction of the advancing wave.
C)It causes the rock to wiggle from side to side as the wave advances.
D)It causes the rock to move in little vertical circles as the wave advances.

Question 71

What characterizes P-wave arrivals on the far side of the Earth at epicentral angles beyond 140°?

A)They are amplified in intensity by the Ni-Fe in the core.
B)They arrive sooner than expected because of the abrupt increase in velocity at the mantle-core boundary.
C)They are slowed by about 40% due to refraction through the outer core.
D)The waveforms of their signals are all upside down due to coming out the other side of the Earth.

Question 72

The P-wave shadow zone is largely the result of ________.

A)reflection of P waves from the inner core-outer core boundary
B)lower P-wave velocities in the mantle than in the crust
C)refraction of P waves deeper into the core upon crossing the mantle-outer core boundary
D)reflection of P waves at the boundary between the inner and outer cores

Question 73

Note the length of rupture for Canada's largest historic earthquake of ML 8.1 on the Queen Charlotte Fault in Fig.10.20.Assuming that total rupture area is proportional to quake magnitude and energy released, what is the maximum size quake (ML)that could occur if the entire length of the Queen Charlotte Fault were to rupture all at once?

A)8)3
B)8)6
C)9)1
D)14.1

Question 74

The top of the ________ is marked by the Moho discontinuity.

A)mantle
B)inner core
C)crust
D)outer core

Question 75

What does an S-wave do to the rock it passes through?

A)It lifts it up and down in a wavelike motion (perpendicular to the advancing wave front), distorting the rock's shape while holding its volume (and density)constant.
B)It alternately compresses and expands the rock (like the bellows of an accordion)along the direction of the advancing wave.
C)It causes the rock to wiggle from side to side as the wave advances.
D)It causes the rock to move in little vertical circles as the wave advances.

Question 76

________ first recognized the seismic discontinuity between the inner and outer cores.

A)Andrija Mohorovicic
B)Ron Clowes
C)Inge Lehmann
D)Beno Gutenberg

Question 77

What do seismic gaps represent?

A)locked areas that are still accumulating strain
B)areas with no faults
C)places nobody bothered to check because they are so remote
D)really well lubricated places where the government spends enormous expense injecting fluids to keep the fault slipping gradually

Question 78

The ________ transmits P waves but not S waves.

A)outer core
B)crust
C)mantle
D)lithosphere

Question 79

The deepest borehole ever drilled is ________ kilometres deep in Russia's Kola Peninsula.

A)7)1
B)12.3
C)45.0
D)160.0

Question 80

What is the main reason that ray paths of seismic waves are curved like dipping arcs, rather than proceeding along the straightest, shortest path as they pass through the whole earth?

A)The earth gets too hot and the seismic waves steer away into the shallower, colder regions.
B)The rock layers themselves are bent and sagged and the waves actually travel parallel to the distorted rock layers or beds.
C)The stiffest, most brittle rocks near the surface transmit sound waves better.
D)Velocity increases with depth.