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Geo 1 > Quiz 5 > Flashcards

Quiz 5 Flashcards

1
Q

Thought to cause earthquakes before plate tectonics

A

Angry gods, mythical creatures, magma movement, tidal forces, compressed air

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2
Q

Interplate earthquakes and an example of where they occur

A

Occur in plate interiors due to ancient rifts or fault zones. Fluids moving along fault zones can often cause movement
New Madrid Seismic Zone: made up of reactivated faults that formed when what’s now North America began to split/rift apart during the breakup of the supercontinent Rodinia

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3
Q

Hypocenter

A

Also called the focus. It’s the exact position on the fault, including the depth, where slippage began

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4
Q

Epicenter

A

The map position of the earthquake (on the surface), directly above the focus

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5
Q

Types of earthquake faults

A

Normal fault, thrust fault, and strike-slip fault

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6
Q

Normal fault

A

Caused by tension; one plate slides down (divergent boundaries) from tension forces (forces moving apart)

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7
Q

Thrust fault

A

One block moves up over the other from compression forces

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8
Q

Strike-slip fault

A

At a transform boundary; blocks/plates moving past each other from shearing forces

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9
Q

The stored energy that earthquakes release

A

Seismic waves

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10
Q

Body waves include

A

P waves (primary/compression waves) and S waves (secondary/shear waves)

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11
Q

Surface waves include

A

Love waves and Rayleigh waves

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12
Q

What do body and surface waves, respectively, tell us?

A

Body waves tell us where earthquakes might originate
Surface waves tell us about where damage might be done

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13
Q

For surface waves, _______ decreases with ______

A

Amplitude; depth

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14
Q

Particle motion of P waves

A

Alternating compression and dilation. Material returns to its original shape after wave passes

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15
Q

Particle motion of S waves

A

Up-and-down motion that propagates through. Material returns to its original shape after wave passes

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16
Q

Particle motion of Rayleigh waves

A

Elliptical motion (generally retrograde elliptical). Material returns to its original shape after wave passes

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17
Q

Particle motion of Love waves

A

Side-to-side motion that propagates through. Material returns to its original shape after wave passes

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18
Q

The difference between the arrival times of the P and S waves at a recording station is a function of

A

The distance from the epicenter

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19
Q

Scale based on the amount of energy released by the earthquake

A

Richter Magnitude Scale

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20
Q

The amount of energy released by an earthquake is based on measurements of what

A

The amplitude and the P-S wave distance

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21
Q

Scale measuring force, based on the damage done and human perception

A

Modified Mercalli Intensity Scale

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22
Q

Magnitude

A

The amount of energy released by an earthquake

23
Q

Intensity

A

Measure of damage and death that an earthquake causes

24
Q

Each whole number increase in magnitude represents

A

10-fold increase in the measured amplitude on a seismogram
32-fold increase in the energy released by the earthquake

25
Q

Factors affecting earthquake intensity/Mercalli Scale variables

A

Magnitude
Distance away from the focus/epicenter
Foundation materials
Building style
Duration of shaking

26
Q

Intensity of ground motion depends on

A

Geology (loose, unconsolidated sediments are subject to more intense shaking than solid bedrock is)
Size of earthquake (larger earthquake = more intense shaking and longer duration)
Distance of earthquake away from epicenter (more severe near epicenter)

27
Q

Damage due to earthquakes can be caused from a variety of factors (i.e. what other disasters can an earthquake cause?)

A

Collapse
Fire damage
Landslides
Flood
Liquefaction
Tsunami

28
Q

Liquefaction

A

Unconsolidated materials are saturated with water, earthquake vibrations can turn stable soil into a mobile fluid

29
Q

Why could fire damage occur after an earthquake?

A

Power lines knocked down
Natural gas line ruptures
Broken water lines (can’t put out fire)

30
Q

Why could flooding occur after an earthquake?

A

Dams can give way during/after an earthquake

31
Q

Factors of Seismic Risk (list, no definitions)

A

Hazard, Vulnerability, Value

32
Q

Hazard

A

The chance that the building will experience strong shaking, soil liquefaction, or a landslide

33
Q

Vulnerability

A

The likelihood that the building will collapse due to those geological hazards

34
Q

Value

A

The number of lives potentially affected

35
Q

Mean Recurrence Interval (MRI)

A

Average time between earthquakes, calculated by 1/avg number of earthquakes
If earthquake number over 30 years is unknown, then plot out previous MRIs

36
Q

To calculate the probability of an earthquake occurring over any number of years

A

1 - (probability of an earthquake NOT occurring)^years

37
Q

To calculate the probability that an earthquake will occur over the course of a year

A

1/MRI, not to exceed 1 or 100%

38
Q

Brittle building materials

A

Concrete and masonry

39
Q

Flexible building materials

A

Wood and steel

40
Q

Materials that are particularly prone to damage

A

Wood and unreinforced masonryS

41
Q

Ways to make buildings more safe against earthquakes

A

Lower height
Move weight to lower floors
Change building shape
Change building materials
Shear walls
Braced frames
Base isolation
Retrofit older structures
Seismic dampeners (reduces the maximum amplitude of a wave passing through the object)

42
Q

Vulnerability factors include:

A

Soft stories
Unreinforced masonry (brick/concrete without reinforcement)
Vertical irregularity (different building parts at different heights) or plan irregularity (deviation from a box shape)

43
Q

Rough steps to the formation of an ocean basin

A
  1. Upwelling of ocean mantle material, causing the crust above it to thin and upwarp, which later leads to the faulting and breaking of rocks
  2. The crust is broken and stretched, producing a rift valley
  3. Continental rifting eventually produces a linear sea
  4. If spreading continues, the sea will develop into a full-on ocean
44
Q

What types of rocks are you likely to find at oceanic ridges?

A

Igneous, mafic, fine-grained rocks: mainly basalt, but sometimes gabbro if cooling occurs below the ocean floor

45
Q

What are two methods for volcanic monitoring?

A

Seismic monitoring; measuring deformation and tilt

46
Q

Equipment needed for measuring deformation and tilt

A

Tilt meter, GPS

47
Q

Equipment needed for seismic monitoring

A

Seismogram, seismometer

48
Q

Data collected from seismic monitoring

A

Seismograph

49
Q

Data collected from measuring deformation and tilt

A

GPS station motion

50
Q

“Signature” of volcanic eruption about to occur, from a seismic monitoring standpoint

A

Earthquakes, which develop into longer tremors with more sustain (much larger earthquakes occur before the eruption, with a much longer duration seismogram)
Continuous release of seismic energy from magma moving

51
Q

“Signature” of volcanic eruption about to occur, from the standpoint of measuring tilt and deformation

A

Magma causes the surface to transform (bulges and moves upward)
The tilt of the surface changes

52
Q

___ is released before a volcanic eruption

A

Gas

53
Q

Explain why divergent plate boundaries do(n’t) cause tsunamis

A

They don’t cause earthquakes – divergent plate boundaries make more space for water, so even with earthquakes, you won’t get tsunamis at that location.
Additionally, the upward force causing tsunamis comes from convergent boundaries.

Geo 1 (7 decks)

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