Deck 7: Earthquakes and the Earths Structure

Question 1

____________________ are small earthquakes that precede a large quake by an interval ranging from a few seconds to a few weeks but are not good predictors of earthquakes because they do not occur in all earthquake events.

Answer 1

Foreshocks

Question 2

The San Andreas Fault represents a ______________ fault because the rocks on opposite sides move horizontally.

Answer 2

strike-slip

Question 3

____________________ are compressional waves and can travel through gases, liquids, and solids.

Answer 3

P waves

Question 4

The deflection of S-waves in what specific part of the Earth's interior proved that the outer core is liquid and causes the Earth's magnetic field to form?

Question 5

If rock exceeds the limit beyond which it cannot deform elastically, what will happen to the rock? _____________

Question 6

____________________ ____________________ are elastic waves that travel through rock and are produced by earthquakes.

Question 7

Earthquakes are motion or trembling of Earth caused by the abrupt release of ____________ stored in rock?

Question 8

The boundary between the crust and the mantle is known as the ____________________ and the speed of P and S waves increase in this region indicating that a composition change occurs inside the Earth.

Question 9

The initial rupture point of an earthquake (below Earth's surface) is the ____.

A) focus
B) disaster zone
C) seismic center
D) epicenter

Question 10

If you were a seismologist, you would study ________________ from a seismograph in order to evaluate an earthquake's body and surface wave characteristics.

A) Earth's temperature
B) magnetic anomalies
C) seismic waves
D) isostasy

Question 11

Earthquakes are detected and measured with a device called a(n) ____________________.

Question 12

Most movement of crustal rock occurs due to slippage along established ____________________.

Question 13

The initial rupture point of an earthquake, where abrupt movement occurs, is the ____________________ and its distance from the Earth's surface influences the potential damage the earthquake will cause.

Question 14

A seismologist would expect less damage to occur from ____________ waves rather than surface waves because these waves travel through rock and carry some energy to the Earth's surface.

Question 15

A rock that has deformed ____ under stress keeps its new shape when the stress is released.

A) elastically
B) nonpermanently
C) plastically
D) flexibly

Question 16

Modern seismologists typically use which scale to most accurately assess the total amount of energy released in an earthquake? __________________

A) Mercalli Scale
B) Benioff Scale
C) Richter Scale
D) Moment magnitude

Question 17

When stressed by a tectonic force, rock stores elastic energy that causes deformation, or ____, to build.

A) compression
B) strain
C) fractures
D) vibrations

Question 18

A seismologist would expect more damage to occur from _____________ waves rather than body waves because these seismic waves shake and bounce structures at the surface.

Question 19

If you were in an earthquake where the ground rolled up and down, what specific type of surface wave did you experience?

Question 20

Most earthquakes occur along ____________________ boundaries.

Question 21

Which specific type of body wave traveled through the Earth's inner core indicating it is a solid rather than liquid in composition?

A) P waves
B) S waves
C) Raleigh waves
D) Love waves

Question 22

In earthquake-prone areas, ____ is the best foundation choice for building your home

A) Clay
B) Bedrock
C) sandy-clay
D) silty-clay

Question 23

S, or shear, waves ____.

A) are faster than P waves
B) move through solids, liquids, and gases
C) move along Earth's surface only
D) vibrate perpendicular to the direction they travel

Question 24

P, or primary, waves ____.

A) are characterized by alternate compression and expansion of rock
B) are the slowest waves generated by an earthquake
C) pass through liquids only
D) move along Earth's surface only

Question 25

Earth's deepest borehole is located in northern ____ and extends to a depth of 12 kilometers.

A) China
B) Russia
C) Iceland
D) Canada

Question 26

____ is a continuous, slow movement of solid rock along a fault, usually not causing large earthquakes.

A) Fracturing
B) Fault slipping
C) Fault creep
D) Strike-slip

Question 27

P waves and S waves ____.

A) move along Earth's surface only
B) travel through Earth's interior
C) do not reflect and refract at boundaries
D) are the principal source of movement and damage on the surface

Question 28

____ are not considered a reliable tool for short-term prediction of earthquakes because they precede only about half of earthquakes and many times, are not followed by a large quake.

A) Foreshocks
B) Seismic waves
C) P waves
D) Tsunamis

Question 29

Earth's magnetic field is created within the ____ because it is a liquid and spins around the solid ______.

A) inner core and outer core
B) outer core and inner core
C) lower mantle and upper mantle
D) upper mantle and lower mantle

Question 30

As a geologist, you would predict what natural disaster to occur as a consequence of earthquakes in hilly areas where liquefaction happened?

A) Volcanic eruptions
B) Landslides
C) Tsunamis
D) Fault scarps

Question 31

When a wave passes from one material to another, it ____ (bends) and sometimes ____ (bounces back).

A) reflects; refracts
B) compresses; refracts
C) refracts; reflects
D) reflects; compresses

Question 32

The San Andreas Fault zone is an example of a(n) ____.

A) earthquake zone at a transform plate boundary
B) Benioff zone
C) earthquake zone at a subduction plate boundary
D) earthquake zone at a divergent plate boundary

Question 33

Earthquakes at convergent plate boundaries tend to occur in the ____.

A) travel-time curve
B) Mercalli zone
C) Benioff zone
D) Richter zone

Question 34

Friction is the process that prevents tectonic plates from ______________ past one another continuously and can cause build-up of stress in a fault like the San Andreas.

A) Subducting
B) Colliding
C) Slipping
D) Pulling

Question 35

The Mercalli scale measures ____.

A) numbers of earthquake waves generated
B) the intensity of an earthquake based on its destructive power
C) the amount of energy released during an earthquake based on the largest recorded body wave
D) the amount of energy released during an earthquake based on the amount of movement and fault area

Question 36

Rock deforms ____ under small amounts of stress and returns to its original shape and size when the stress is removed such as folds.

A) elastically
B) plastically
C) seismically
D) fracturally

Question 37

The Mohorovicic discontinuity was identified through the passage of seismic waves between the ____ and the ____.

A) inner core; outer core
B) upper mantle; lower mantle
C) crust; mantle
D) mantle; core

Question 38

The New Madrid fault zone in the United States is thought to be caused by ____.

A) weaknesses in the lithosphere resulting from the failed development of a divergent boundary
B) a Precambrian convergent zone
C) sand volcanoes
D) a prehistoric strike-slip fault

Question 39

The moment magnitude scale ____.

A) is based on the highest peak recorded on a specific type of seismograph
B) can be used to locate the earthquake epicenter
C) more closely reflects the total amount of energy released during an earthquake
D) is measured by recording the amount of structural damage in an area

Question 40

During the process of liquefaction, soil loses its shear strength and behaves like a ______________.

A) Solid
B) Liquid
C) Fault
D) Fracture

Question 41

As a seismologist, you would have expected the Tohoku earthquake to have a shorter rupture in the fault zone as compared to the Sumatra-Andaman earthquake.

Question 42

A seismologist would predict that a tsunami produced by an undersea earthquake could travel at 750 kilometers per hour and grow in substantial height as the wave approaches shoreline where friction slows the wave speed down.

Question 43

Where two tectonic plates move past one another, rock near the plate boundary can stretch or compress elastically for decades, and then fracture suddenly and create an earthquake.

Question 44

Geologists use a travel-time curve to calculate the distance between the earthquake epicenter and the earthquake focus.

Question 45

Seismologists rely on foreshocks as an indicator of when a large earthquake will occur because foreshocks precede all earthquakes and ample seismograph data has been collected on foreshocks.

Question 46

Slippage at the New Madrid fault zone caused the 1906 San Francisco earthquake because the fault zones are connected allowing for fracturing to occur.

Question 47

The most likely source of Earth's magnetism is ____.

A) the flow and convection of liquid metals in the outer core
B) a permanent magnet that oscillates within Earth's core
C) the energy received by the Sun
D) convection currents in the mantle

Question 48

An area with granite bedrock would be highly prone to liquefaction during a major earthquake.

Question 49

Seismologists have found evidence that all of the 30 strongest earthquakes recorded since 1900 have occurred at transform plate boundaries where the impact of colliding plates causes fracturing and faulting of rocks.

Question 50

In order to determine the epicenter of an earthquake, you would need a minimum of 3 seismograph station seismograms to determine the arrival time of both P and S waves.

Question 51

A geologist would identify _____________ as the cause of the 2004 Sumatra-Andaman earthquake.

A) fault rupture
B) strike-slip
C) tsunami
D) divergent boundary

Question 52

Which procedure is used in short-term predictions of earthquakes?

A) measurements of coastal marsh sediments near subduction zones
B) measurements of changes in the land surface near an active fault zone
C) monitoring of P wave formation
D) monitoring of tidal wave formation

Question 53

If a geologist found evidence of tsunami deposits, submergence of coastal forests from ground displacement, fault rupture, results from computer models and historic documents about an ancient earthquake that occurred in 1700, this would be sufficient data to determine an earthquake occurred at that time.

Question 54

The monitoring of the electrical conductivity of rock near fault zones is used in long-term predictions of earthquakes and seismologists rely upon this data to help determine where microscopic cracks develop in the rock.

Question 55

If a large earthquake with a shallow focus occurred in a region like Haiti that has loose sediments and limited bedrock, the man-made structures created with brick and mortar and concrete that is not reinforced would be a high risk for building failure.

Question 56

P and S waves travel more slowly in the Moho than they do in the crust or below the asthenosphere because the composition changes from basalt to peridotite which is a more dense rock material which slows the speed of the body waves down.

Question 57

The boundary in the mantle where composition changes allows seismic wave velocities to do what because pressure is great enough that the minerals in the mantle recrystallize to form denser minerals such as peridotite is called the 660-kilometer discontinuity.

A) Velocity decreases
B) Velocity increases
C) Velocity remains the same
D) None of the above

Question 58

Which of the following building materials normally bend and sway during an earthquake?

A) steel
B) brick
C) adobe
D) stone

Question 59

If you were examining Richter Scale readings from earthquakes at mid-oceanic ridges, you would expect their focus to be deeper and stronger than earthquakes that form at convergent plate.

Question 60

Long-term predictions of when earthquakes will occur are fairly accurate because seismologists have ample seismograph data that indicate specific increments of time between large earthquakes.

Question 61

Explain how earthquake mortality is linked to the economic status of a region.

Question 62

Discuss how the structural damage in an earthquake relates to the magnitude, geology, and urbanized areas.

Question 63

Explain why shallow earthquakes occur at mid-oceanic ridges and deeper earthquakes occur at subduction zones.

Question 64

Discuss which type of surface wave causes more damage to human structures and the surface.

Question 65

Explain what best practices that engineers employee to reduce the potential for structural failure in regions with sand sediment and soil during an earthquake.

Question 66

Explain why the core has a much higher density as compared to the crust and mantle.

Question 67

Discuss which type of seismic wave causes more damage to human structures and the surface.

Question 68

Explain why long-term prediction of earthquakes is more accurate than short-term prediction.

Question 69

Explain why shallow focus earthquakes at subduction zones cause more damage than deeper focus earthquakes.

Question 70

Explain why seismologists use a travel-time curve to calculate the distance between an earthquake epicenter and a seismograph station.

Question 71

Explain how scientists have determined the composition and structure of the mantle.

Question 72

Explain how a big earthquake on the Richter scale could cause limited damage on the Earth's surface.

Question 73

Explain why the Sumatra-Andaman earthquake lasted for up to 10 minutes.

Question 74

Explain how plate boundaries from the Precambrian Eon have impacted the New Madrid fault zone today.

Question 75

Describe how liquefaction occurs in an earthquake.

Question 76

Explain why moment magnitude is preferred by most seismologists to calculate the energy released in an earthquake as compared to Richter scale.

Question 77

Explain why seismic waves speed up at discontinuities such as the Moho and slow back down in the mantle.

Question 78

Explain why the Mexico City earthquake of 1985 destroyed much of that city but caused very little damage in Acapulco which was closer to the epicenter.

Question 79

Explain how the estimated 9.0 moment magnitude rating of the 1700 Cascadia earthquake was determined.

Question 80

Explain why many of the world's strongest earthquakes occur in subduction zones.