Quiz 5

Question 1

Thought to cause earthquakes before plate tectonics

Answer 1

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

Question 2

Interplate earthquakes and an example of where they occur

Answer 2

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

Question 3

Hypocenter

Answer 3

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

Question 4

Epicenter

Answer 4

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

Question 5

Types of earthquake faults

Answer 5

Normal fault, thrust fault, and strike-slip fault

Question 6

Normal fault

Answer 6

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

Question 7

Thrust fault

Answer 7

One block moves up over the other from compression forces

Question 8

Strike-slip fault

Answer 8

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

Question 9

The stored energy that earthquakes release

Answer 9

Seismic waves

Question 10

Body waves include

Answer 10

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

Question 11

Surface waves include

Answer 11

Love waves and Rayleigh waves

Question 12

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

Answer 12

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

Question 13

For surface waves, _______ decreases with ______

Answer 13

Amplitude; depth

Question 14

Particle motion of P waves

Answer 14

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

Question 15

Particle motion of S waves

Answer 15

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

Question 16

Particle motion of Rayleigh waves

Answer 16

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

Question 17

Particle motion of Love waves

Answer 17

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

Question 18

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

Answer 18

The distance from the epicenter

Question 19

Scale based on the amount of energy released by the earthquake

Answer 19

Richter Magnitude Scale

Question 20

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

Answer 20

The amplitude and the P-S wave distance

Question 21

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

Answer 21

Modified Mercalli Intensity Scale

Question 22

Magnitude

Answer 22

The amount of energy released by an earthquake

Question 23

Intensity

Answer 23

Measure of damage and death that an earthquake causes

Question 24

Each whole number increase in magnitude represents

Answer 24

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

Question 25

Factors affecting earthquake intensity/Mercalli Scale variables

Answer 25

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

Question 26

Intensity of ground motion depends on

Answer 26

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)

Question 27

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

Answer 27

Collapse Fire damage Landslides Flood Liquefaction Tsunami

Question 28

Liquefaction

Answer 28

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

Question 29

Why could fire damage occur after an earthquake?

Answer 29

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

Question 30

Why could flooding occur after an earthquake?

Answer 30

Dams can give way during/after an earthquake

Question 31

Factors of Seismic Risk (list, no definitions)

Answer 31

Hazard, Vulnerability, Value

Question 32

Hazard

Answer 32

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

Question 33

Vulnerability

Answer 33

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

Question 34

Value

Answer 34

The number of lives potentially affected

Question 35

Mean Recurrence Interval (MRI)

Answer 35

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

Question 36

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

Answer 36

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

Question 37

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

Answer 37

1/MRI, not to exceed 1 or 100%

Question 38

Brittle building materials

Answer 38

Concrete and masonry

Question 39

Flexible building materials

Answer 39

Wood and steel

Question 40

Materials that are particularly prone to damage

Answer 40

Wood and unreinforced masonryS

Question 41

Ways to make buildings more safe against earthquakes

Answer 41

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)

Question 42

Vulnerability factors include:

Answer 42

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

Question 43

Rough steps to the formation of an ocean basin

Answer 43

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

Question 44

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

Answer 44

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

Question 45

What are two methods for volcanic monitoring?

Answer 45

Seismic monitoring; measuring deformation and tilt

Question 46

Equipment needed for measuring deformation and tilt

Answer 46

Tilt meter, GPS

Question 47

Equipment needed for seismic monitoring

Answer 47

Seismogram, seismometer

Question 48

Data collected from seismic monitoring

Answer 48

Seismograph

Question 49

Data collected from measuring deformation and tilt

Answer 49

GPS station motion

Question 50

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

Answer 50

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

Question 51

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

Answer 51

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

Question 52

___ is released before a volcanic eruption

Answer 52

Gas

Question 53

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

Answer 53

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.