Deck 5: Weathering and Soil

Question 1

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

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

Answer 1

B

Question 2

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) because P- wave speeds are higher in the outer core than in the lower mantle
C) by analysis of the P- wave and S- wave shadow zones
D) by using the ratio of iron meteorites to stony meteorites to deduce the relative diameters of the core and mantle

Answer 2

C

Question 3

The earthquake was accompanied by extensive fire damage.

A) Anchorage, 1964
B) Armenia, 1988
C) Mexico City, 1985
D) San Francisco, 1906

Answer 3

D

Question 4

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 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.
C) 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.
D) The volume of the rock stays fixed, but it shears back and forth, distorting the rocks internal shape as the wave passes through.

Question 5

What do seismic gaps represent?

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

Question 6

Which one the following does not propagate through liquids?

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

Question 7

Which one of the following statements is correct?

A) P waves travel through solids; S waves do not.
B) S waves travel through solids and P waves travel through liquids.
C) P and S waves travel through liquids, but P waves do not travel through solids.
D) P and S waves travel through liquids, but S waves do not travel through solids.

Question 8

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

Question 9

What causes the shadow zone for no S- wave arrivals beyond epicentral angles of 105°?

A) All seismographs are located on the near side of the earth.
B) All shear waves are converted to surface waves at the mantle- core boundary.
C) The Earth is hollow.
D) 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.

Question 10

The transmits P waves but not S waves.

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

Question 11

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

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

Question 12

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) 2 min
B) 2000 min
C) 7.5 min
D) 4 min

Question 13

is the maximum possible damage designation on the Mercalli scale.

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

Question 14

The of the Earth does not transmit S waves.

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

Question 15

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

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

Question 16

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

A) It alternately compresses and expands the rock (like the bellows of an accordion) along the direction of the advancing wave. This "preserves the rock's shape", while changing its density in a periodic fashion.
B) 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.
C) It causes the rock to move in little vertical circles as the wave advances.
D) It causes the rock to wiggle from side to side as the wave advances.

Question 17

How many destructive tsunamis are there each year?

A) 5- 10
B) 100- 200
C) 10- 25
D) 1- 2

Question 18

is the widely accepted explanation for the mechanism that generates earthquakes.

A) Richter's wave- snap theory
B) Dow's recovery theory
C) Reid's elastic rebound theory
D) Dupont's plastic- slip theory

Question 19

The fact that is good evidence for a solid inner core

A) P waves are faster in the inner core than in the outer core
B) S waves are focused at the centre of the P- wave shadow zone
C) S waves are slower in the inner core than in the outer core
D) S waves do not pass directly through the core

Question 20

Seismic gaps are .

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

Question 21

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

A) 0.5
B) 4.0
C) 1.0
D) 2.0

Question 22

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

A) 160.0
B) 12.3
C) 7.1
D) 45.0

Question 23

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

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

Question 24

Approximately how many years must elapse before all segments of the Pacific- North America boundary build up and release enough strain as great earthquakes, to trace out the entire plate boundary?

A) 50
B) 5
C) 200
D) 20

Question 25

The is the point of origination for an earthquake.

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

Question 26

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

A) The wave front seeks out the instrument which stops vibrating when the wave front reaches it.
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 focus.
D) 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.

Question 27

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

A) The volume of the rock stays fixed, but it shears back and forth, distorting the rocks internal shape as the wave passes through.
B) 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.
C) 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.
D) The little parcel of rock rotates about its own location in an ellipse until the wave passes.

Question 28

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

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

Question 29

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

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

Question 30

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 causes the rock to move in little vertical circles as the wave advances.
C) It alternately compresses and expands the rock (like the bellows of an accordion) along the direction of the advancing wave. This "preserves the rock's shape", while changing its density in a periodic fashion.
D) It causes the rock to wiggle from side to side as the wave advances.

Question 31

P waves .

A) are faster than S waves and surface waves
B) propagate only in solids
C) have higher amplitudes than do S waves
D) produce the strongest ground shaking

Question 32

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

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

Question 33

How deep are the deepest earthquakes?

A) < 5 km
B) 70- 300 km
C) 5- 70 km
D) 300- 700 km

Question 34

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

A) 43.8
B) 4.38
C) 263
D) 4.66

Question 35

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) 1.0
B) 4.0
C) 1.5
D) 2.0

Question 36

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

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

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 great circle route that passes through the north pole
C) the shortest distance through the Earth between the earthquake and your station (like the chord across a circle)
D) the longest great circle route that passes through your station

Question 38

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

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

Question 39

What acoustic phenomenon causes the shadow zone for P-wave arrivals at epicentral angles between 105° and 140°?

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

Question 40

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

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

Question 41

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

A) zones of rupture for a singe great earthquake string out along the fault intermittently with intact regions like tears on a dotted line
B) 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
C) a clear pattern is bound to emerge eventually, if only we wait long enough
D) individual rupture zones tend to occur adjacent to one another, without appreciable overlap, tracing out the plate boundary

Question 42

Which one of the following is true regarding tsunamis?

A) Their wave heights decrease and wavelengths increase as they move into shallower water.
B) 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.
C) 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.
D) 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.

Question 43

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

A) 500
B) 4.66
C) 8.33
D) 200

Question 44

How was the Turnagain Heights area of Anchorage, Alaska, damaged during the 1964 earthquake?

A) Rioting by frenzied inhabitants in Anchorage's worst slum area.
B) A weak, subsurface, clay layer failed, resulting in numerous rotational landslides.
C) It burned in a fire set off by broken gas lines.
D) It was hit by a large tsunami and then buried by a rock avalanche.

Question 45

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

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

Question 46

Why was the Loma Prieta area, California heavily damaged in the 1989 quake?

A) Liquefaction in unconsolidated, water- saturated soils and fill caused foundation failures.
B) The area is built on consolidated rock, causing the shaking to be amplified.
C) Shaking was no more extensive than elsewhere in the city, but the whole district burned following each quake.
D) The epicentres of both quakes were right under the district.

Question 47

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

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

Question 48

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

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

Question 49

Most large earthquakes result from .

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

Question 50

How is Moment Magnitude (MW ) calculated?

A) 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
B) from surface wave magnitude measured one minute after the first P- wave arrival
C) from the amount of building or other infrastructure damage in large earthquakes with more than one minute of of ground shaking
D) from S- wave magnitude measured one minute before the last P- wave arrival

Question 51

formulated the elastic rebound theory after the earthquake.

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

Question 52

The is a direct measure of the distance from a seismic station to the focus of a distant earthquake.

A) time elapsed between the first P- wave arrivals from the first and last aftershocks
B) time interval between the first P and S- wave arrivals
C) magnitude of the ground acceleration of surface wave passing a station
D) how long before the earthquake your animals started acting agitated

Question 53

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

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

Question 54

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

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

Question 55

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

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

Question 56

Which of the following statements is true?

A) 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.
B) Tsunamis only travel short distances so coastal areas have to be close to the epicentre to be in any real danger.
C) 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.
D) Tsunamis stop when they reach a shoreline so people are safe as long as they stay inland.

Question 57

Note the length of rupture for Canada's largest historic earthquake of ML 8.1 on the Queen Charlotte Fault in Fig. 10.21. 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) 9.1
B) 8.3
C) 8.6
D) 14.1

Question 58

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) open- ended Richter
C) moment magnitude
D) shaklee natural

Question 59

The epicentre of an earthquake is the .

A) surface location directly above the point where the fault slip initiates
B) point where the minimum ground shaking is recorded
C) point where the fault cracking initiates
D) point of most costly structural damage associated with ground shaking

Question 60

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

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

Question 61

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

Question 62

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

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

Question 63

Which one of the following best characterizes tsunamis?

A) They are easily seen at sea but are lost in the swell and breaking waves along a coast.
B) They are faster than seismic surface waves.
C) They cause the land to ripple and oscillate.
D) They have relatively small amplitudes compared to their very long wavelengths.

Question 64

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

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

Question 65

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

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

Question 66

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) seismograph; Richter
C) vibrator; Dr. Ruth
D) polygraph; Freud

Question 67

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

A) meteorite impacts during solar flares
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) gas venting from underlying hydrocarbon deposits

Question 68

have the highest velocities.

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

Question 69

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

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

Question 70

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

A) 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.
B) The volume of the rock stays fixed, but it shears back and forth, distorting the rocks internal shape as the wave passes through.
C) 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.
D) The little parcel of rock rotates about its own location in an ellipse until the wave passes.

Question 71

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

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

Question 72

The largest lateral, ground displacement experienced at any location is produced by .

A) vertically vibrating P waves refracted across the Moho
B) first P arrival reflecting from the inner- outer core boundary
C) the S wave reflected from the core- mantle boundary
D) horizontally vibrating surface waves

Question 73

The Mercalli Scale is a scale from .

A) I to XII that rates the structural damage due to an earthquake
B) I to X that rates the total energy released during the main quake and all aftershocks
C) 1 to 12 that rates the energy required for faulting to occur
D) 1 to 10 that rates the energy released by an earthquake

Question 74

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

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

Question 75

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) They should be straight lines. Earth is flat and the time- travel graph proves it!
C) During an earthquake, Earth shakes so much that it is like a quivering rubber ball and all of the distances are wrong.
D) They have to bend with the curvature of the Earth.

Question 76

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

A) You dig up your seismograph and take it to a destitute seismologist and offer to trade the instrument for the answer to your question!
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) by measuring the P- wave arrival time and its intensity and using a formula

Question 77

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) 32 times
C) 10 times
D) 100 times

Question 78

On a typical seismogram, will show the highest amplitudes.

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

Question 79

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) 2000 km
B) 2450 km
C) 2150 km
D) 950 km

Question 80

Which of the following statements is true?

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