Deck 3: Earthquake Geology and Seismology

Question 1

Transform faults have mostly vertical displacement rather than horizontal displacement.

Answer 1

False

Question 2

Large earthquakes do not generate body waves energetic enough to be recorded on seismographs all around the world.

Answer 2

False

Question 3

To describe the location in three-dimensional space of a deformed rock layer or a fault surface,geologists make measurements known as dip and strike.

Answer 3

True

Question 4

The point where a fault first ruptures underground is known as the epicenter.

Question 5

P- and S-waves do not follow simple paths as they pass through the Earth;they speed up,slow down,and change direction,and S-waves even disappear when they reach the Earth's core.

Question 6

The shallower the hypocenter,the more P- and S-wave energy will hit the surface,thus putting less energy into Rayleigh waves.

Question 7

The biggest shaking event is called "the earthquake," the smaller ones before it are known as foreshocks,and the smaller ones after it are called aftershocks.

Question 8

Transform faults usually link spreading centers or connect spreading centers with subduction zones.

Question 9

Moving into the core,P-wave velocities gradually increase until a positive jump is reached at about a 5150-km depth,suggesting that the inner core is solid.

Question 10

The Earth's interior is homogeneous.

Question 11

In igneous rocks such as granite,S-waves travel about 1.7 times faster than P-waves.

Question 12

Following the paths of P- and S-waves from the Earth's surface inward,there is an initial increase in wave speed but then a marked slowing occurs at a depth of about 100 feet;this defines the top of the lithosphere.

Question 13

Aftershocks are smaller than the main shock in an earthquake sequence.

Question 14

Normal faulting occurs when the hanging wall moves upward relative to the footwall.

Question 15

Both Love and Rayleigh waves are referred to as L waves (long waves)because they take longer periods of time to complete one cycle of motion and are slower moving relative to P- and S-waves.

Question 16

With their up-and-down and side-to-side motions,S-waves shake the ground surface and can do severe damage to buildings.

Question 17

The velocity of an S-wave depends on the density and resistance to shearing of materials.

Question 18

The shaking produced by Rayleigh waves causes both vertical and horizontal movement.

Question 19

Passing through the mantle below the asthenosphere,the seismic wave velocities vary but generally increase until about 2900-km depth where P-waves slow markedly and S-waves disappear at the core-mantle boundary zone.

Question 20

It is the horizontal fault movements at subduction zones that most commonly cause tsunami,mostly in the Pacific Ocean.

Question 21

Typically fewer than 20 major and great earthquakes (magnitudes of 7 and higher)each year account for more than 90 percent of the energy released by earthquakes.

Question 22

The moment magnitude is more accurate than the classical Richter scale because it is tied directly to physical parameters such as fault-rupture area,fault slip,and energy release,and because other earthquake scales use indirect measures such as how much a seismograph needle moves.

Question 23

Earthquake intensity scales such as the Modified Mercalli scale assess the effects on people and buildings.

Question 24

Low-frequency surface waves will be amplified in tall buildings with low frequencies of vibration.

Question 25

The two largest moment magnitudes measured to date are the 1964 Alaska earthquake (M_S of 8.3;M_W of 9.2)and the 1960 Chile earthquake (M_S of 8.5;M_W of 9.5).

Question 26

The time of day of an earthquake is not a critical factor affecting loss of life from earthquakes.

Question 27

The high-frequency seismic waves are most energetic for short distances close to the epicenter,whereas low-frequency seismic waves carry significant amounts of energy for much greater distances away from the epicenter.

Question 28

Different estimates of earthquake magnitude are derived from different methods based on local shaking (Richter scale),body waves (m_b),surface waves (M_S),or seismic moment (M_W).

Question 29

The Richter scale assesses the 1906 San Francisco earthquake and the 1964 Alaska earthquake as both being of magnitude 8.3.However,on the moment magnitude scale,the San Francisco earthquake is probably equivalent to a Richter magnitude 7.8 and the Alaska seism is equivalent to a 9.2.The Alaska earthquake was at least 100 times bigger.

Question 30

Earthquakes are most commonly caused by ______________.

A)explosions of nuclear bombs
B)undersea landslides
C)meteorite impacts
D)volcanic activity
E)sudden earth movements along faults

Question 31

Some major faults acting for millions of years have offset rock layers horizontally by hundreds of kilometers.

Question 32

For magnitudes above about 6,the bigger earthquake magnitude means that more people in a larger area and for a longer time will experience the intense shaking.

Question 33

The duration of the shaking is not a significant factor in damages suffered and lives lost.

Question 34

The relation between distance and damage from an earthquake seems obvious: the closer to the hypocenter/epicenter,the greater the damage,but this is not always the case.

Question 35

Each year,the Earth is shaken by millions of earthquakes.

Question 36

Earthquake magnitude scales such as the Richter scale assess the effects on people and buildings.

Question 37

The acceleration due to gravity is 9.8 meters per second squared (32 feet per second squared),which is referred to as 1.0 g and is used as a comparative unit of measure.Earthquake accelerations have never been measured in excess of 1.0 g.

Question 38

Where the frequencies of seismic waves match the natural vibration frequencies of local geology and buildings,destruction may be great.

Question 39

The types of rock or sediment on which a structure's foundation sits are of paramount importance with respect to whether the structure will be damaged by shaking from an earthquake.

Question 40

High-frequency P- and S-waves will have their vibrations amplified by 1)rigid construction materials,such as brick or stone,and 2)short buildings.

Question 41

_________ waves are transverse waves that propagate by shearing or shaking particles in their path at right angles to the direction of advance.

A)Love
B)Rayleigh
C)P-
D)S-
E)Both Love and S

Question 42

With compressional forces,the hanging wall moves upward relative to the footwall;this type of fault is referred to as a __________ fault.

A)reverse
B)subnormal
C)transform
D)strike-slip
E)normal

Question 43

The __________ is measured in cross-sectional view as the angle of inclination from horizontal of a tilted rock layer,and _______ is viewed in map view as the compass bearing of the rock layer where it intersects a horizontal plane.

A)strike;strike
B)dip;dip
C)strike;dip
D)dip;strike
E)strike and dip;strike and dip

Question 44

P-waves can travel through ________________.

A)gases
B)liquids
C)solids
D)a vacuum
E)gases,liquids,and solids

Question 45

When most of the movement along a fault is horizontal,the fault is referred to as a __________ fault.

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

Question 46

The strike-slip San Andreas Fault in California is a _______ fault more than 800 miles long.

A)right-lateral
B)left-lateral
C)thrust
D)normal

Question 47

Can the same fault be classified as both a strike-slip and a transform fault?

A)yes
B)no
C)only if it is also a reverse fault
D)only if it is also a normal fault

Question 48

Despite the profound effects that earthquakes have had on civilizations for so many centuries,systematic scientific observations were not made until the early _________ century,when good descriptions were made of earthquake effects on the land.

A)thirteenth
B)seventeenth
C)eighteenth
D)nineteenth
E)twentieth

Question 49

Velocities for _________ waves in granite are about 5.5 to 6 km/sec,but in water they slow to 1.5 km/sec.

A)Love
B)Rayleigh
C)P-
D)S-

Question 50

In the ________,Steno stated that in an undeformed sequence of sedimentary rock layers,each sedimentary rock layer is younger than the bed beneath it,but older than the bed above it.

A)law of original continuity
B)law of superposition
C)law of original horizontality
D)law of cosines
E)law of retrogression

Question 51

The _________ explains that sediments (such as sands,gravels,and muds)are originally deposited or settled out of water in horizontal layers.

A)law of original continuity
B)law of superposition
C)law of original horizontality
D)law of cosines
E)law of retrogression

Question 52

A normal fault occurs when the hanging wall moves ________ relative to the footwall.

A)up
B)down
C)to the left
D)to the right

Question 53

The point on the Earth's surface directly above the point where the fault first ruptures is called the ____________.

A)epicenter
B)hypocenter
C)depocenter
D)ethnocenter

Question 54

The _____ wave travels fastest and moves in a push-pull fashion of alternating pulses of compression (push)and extension (pull).

A)Love
B)Rayleigh
C)P-
D)S-

Question 55

The Lisbon earthquakes of 1755 are historically significant because ______________.

A)it was the first time anyone had ever successfully predicted an earthquake
B)the reconstruction efforts after the earthquakes stimulated the Portuguese economy,leading to a century of prosperity for the country
C)they changed the prevailing philosophies of the era,producing a more pessimistic view of the world
D)they resulted in more deaths than any other earthquake,before or after

Question 56

First-order analysis of a seismogram record allows seismologists to do all but which of the following?

A)to identify the different kinds of seismic waves generated by the fault movement
B)to estimate the amount of energy released (magnitude)
C)to locate the epicenter and hypocenter
D)to develop a Modified Mercalli Intensity map

Question 57

Faults on which the dominant forces are extensional are recognized by the separation of the pulled-apart rock layers in a zone of omission.These are ____________.

A)reverse faults
B)thrust faults
C)transform faults
D)strike-slip faults
E)normal faults

Question 58

Steno's _____________ states that sediment layers are continuous,ending only by butting up against a topographic high,such as a hill or a cliff,by pinching out due to lack of sediment,or by gradational change from one sediment type to another.

A)law of original continuity
B)law of superposition
C)law of original horizontality
D)law of cosines
E)law of retrogression

Question 59

________ faults are commonly found at areas of plate convergence where subduction or continental collision occurs.

A)Reverse
B)Normal
C)Transform
D)Strike-slip

Question 60

Which of the following wave types travels slowest through rock?

A)P-waves
B)S-waves
C)surface waves
D)body waves
E)They all travel with the same velocity.

Question 61

Flexible buildings (made of wood or steel)have a ________ resonant period than a stiffer building (one of brick or concrete).

A)longer
B)shorter
C)period does not depend on building stiffness

Question 62

The ________ waves advance in a backward-rotating,elliptical motion.

A)S-
B)P-
C)Love
D)Rayleigh
E)None of these are correct.

Question 63

Seismic waves that travel only near the Earth's surface are of two main types: _________ waves.

A)S- and Love
B)P- and Rayleigh
C)P- and S-
D)P- and Love
E)Love and Rayleigh

Question 64

The _________ waves' motion is similar to S waves,except it is from side-to-side in a horizontal plane roughly parallel to the Earth's surface.

A)Rayleigh
B)P-
C)Love

Question 65

Usually,the biggest concern in designing buildings to withstand large earthquakes is the ____________ components of movement.

A)upward push from the vertical
B)downward pull from the vertical
C)sideways push from the horizontal

Question 66

The Richter Scale is set up so that for every _______ increase in the amplitude of the recorded seismic wave,the Richter magnitude increases one number,e.g. ,from 4 to 5.

A)two-fold
B)four-fold
C)eight-fold
D)ten-fold
E)hundred-fold

Question 67

The reduction of ______ waves at the core-mantle boundary indicates that the outer core is mostly liquid.

A)S-
B)P-
C)Rossby
D)Love
E)Rayleigh

Question 68

The frequency of a wave is __________________.

A)the amount of displacement of the medium through which the wave is passing
B)the number of waves passing a given point per unit time
C)the time between successive waves
D)the energy of the wave

Question 69

_________ waves travel only through solids;on reaching liquid or gas,the _______ wave energy is reflected back into rock or is converted to another form.

A)S-
B)P-
C)Rossby-
D)Q-

Question 70

When the Earth shakes,it releases energy in seismic waves,some of which pass through the whole body of the planet (body waves)and some of which propagate only near the surface (_______ waves).

A)Love
B)Rayleigh
C)P-
D)S-
E)Rossby

Question 71

Earthquake moment is calculated by multiplying all but which of the following quantities together?

A)the shear strength of the rocks
B)the rupture area of the fault
C)the average displacement (slip)on the fault
D)the Modified Mercalli Intensity at the epicenter

Question 72

Using the S-P timing method,epicenters can be located using seismograms from a minimum of ______ recording stations.

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

Question 73

The intensity of an earthquake is influenced by all but which one of the following?

A)earthquake magnitude
B)distance from the hypocenter/epicenter
C)type of rock or sediment making up the ground surface
D)the presence of people to record their innermost feelings
E)duration of shaking

Question 74

Earthquake-induced ground motions cause buildings to sway at certain periods.In general,the taller the structure,the _______ the period.

A)longer
B)shorter
C)period does not depend on building height