GOPH 375 > Chapter 3 > Flashcards

Chapter 3 Flashcards

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1
Q

What type of earth material is prone to liquefaction?

A
  • artificial fill

- poorly consolidated sentiment

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2
Q

The second type of seismic wave to reach a recording station after an earthquake is called a ____ wave.

A
  • shear
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3
Q

A seismometer must be installed in contact with ____.

A
  • bedrock
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4
Q

P wave velocity depends upon the material through which the wave passes. Rank these materials from the fastest P velocity at the top

A
  • 1) granite rock
  • 2) packed sand
  • 3) loose sand
  • 4) water
  • 5) air
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5
Q

To determine the _____ of an earthquake, seismologists use a nomograph, which compares the distance from the hypocentre and the amplitude of the seismic waves.

A
  • magnitude
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6
Q

Seismic waves that pass through the interior of the planet are called ____ waves, whereas those that travel across the surface are called ____ waves.

A
  • body

- surface

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7
Q

What phenomenon can cause liquefaction?

A
  • earthquake vibrations

- rapid loading with excess weight

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8
Q

An earthquake occurs from the release of ____ when stress on a fault builds high enough for the rocks to fracture and move suddenly.

A
  • energy
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9
Q

Which of the following describes a primary (P) wave?

A
  • moves in a push-pull fashion
  • the first to reach a recording station
  • can travel through any material
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10
Q

Which of these correctly describe the nature of surface waves?

A
  • slow moving

- low frequency

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11
Q

In which techtonic environment do deep earthquakes occur?

A
  • subduction zones
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12
Q

What is a fault?

A
  • a fracture in bedrock along which sliding has occurred.
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13
Q

The velocity of P waves depends on the ____ and ____ of the material through which they pass.

A
  • density, compressibility
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14
Q

Because of their low frequency and slow speed, surface waves carry ____ amounts of energy away from the epicenter.

A
  • large
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15
Q

What phenomenon can cause liquefaction?

A
  • earthquake vibrations

- rapid loading with excdess weight

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16
Q

An earthquake of Richter magnitude 3 had a S wave amplitude of 1.2mm. What is the Richter magnitude of an earthquake with a S wave amplitude of 12mm, recorded at the same seismograph station?

A
  • 4
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17
Q

The two types of body waves are ____ waves and _____ waves.

A
  • primary

- secondary

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18
Q

The epicenter of an earthquake can be ____.

A
  • underwater
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19
Q

Why does the difference in arrival times between P and S waves increase with epicentral distance?

A
  • P waves travel faster than S waves
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20
Q

Place the four types of seismic waves in order of decreasing velocity, with the fastest at the top.

A
  • P waves
  • S waves
  • Love waves
  • Rayleigh waves
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21
Q

What might people have experiences during an earthquake of intensity IV?

A
  • light sleepers woke up
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22
Q

In which techtonic environment do megathrust earthquakes occur?

A
  • subduction zones
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23
Q

The acceleration due to gravity is ____, which is referred to as 1.0 g.

A
  • 9.8 m/sec2
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24
Q

Because their motion is up and down and side to side, ____ waves are the type of body wave that can do severe damage to buildings.

A
  • secondary
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25
Love waves are a type of surface wave. They are similar to S waves in that they _____.
- cannot travel through fluids but can travel through solid material. - travel with a shearing motion at right angles to their direction of advance.
26
Why was the 2010 Port-au-Prince earthquake so deadly?
- the general population and decision-makers lacked awareness of earthquake risk - several buildings were poorly constructed
27
The rate of change in velocity of the ground as it is moved by seismic waves is called
- acceleration
28
What is the main cause of earthquakes?
- movements along faults
29
Which sections of the San Andreas fault have the highest seismic risk?
- locked zones
30
A ____ is a planar feature where the two rock blocks on either side move past each other.
- fault
31
If, during an earthquake, you feel like you're being rocked in a boat at sea, you are most likely feeling the passage of ____ waves.
- Rayleigh
32
An earthquake occurring in which of the following geological environment will have the largest felt area?
- in the continental interior of North America.
33
Earthquakes are caused by a sudden fault rupture occuring
- at the hypocentre
34
P waves can travel through air, where they take the form of ____ waves.
- sound waves
35
How can you identify an aftershock?
- an aftershock has the same hypocentre as the main shock.
36
Acceleration during an earthquake is usually measured relative to ____.
- acceleration due to gravity
37
How many seismograms are required to locate the epicenter of an earthquake?
- a minimum of 3 seismograms from different stations
38
Charles Richter based his earthquake magnitude scale on the idea that _____.
- the bigger the earthquake, the greater the shaking of the earth.
39
What is the dominant deformation force associated with megathrust faults?
- shear
40
If a wave has a frequency of 20 Hz, what is its period?
- 0.05 s
41
What was the cause of the 2015 Nepal earthquake?
- the collision between the Indian and Eurasian Plates
42
Why are brace frames added to buildings?
- to reinforce the building against horizontal motions
43
Place the four types of seismic waves in order of decreasing velocity, with the fastest at the top.
- P waves - S waves - Love waves - Rayleigh waves
44
Why don't the rocks on either side of a fault simply slide past each other when stress is applied?
- friction holds the rocks together
45
If ten waves are recorded by a seismometer in one second, their frequency is:
- 10 Hz
46
The acceleration due to gravity is ____, which is referred to as 1.0g.
- 9.8m/sec2
47
What is a fault?
- a fracture in bedrock along which sliding has occured.
48
The San Andreas fault is ____.
- a complex system of subparallel transform faults.
49
How can you identify an aftershock?
- an aftershock has the same hypocentre as the main shock.
50
If local soil conditions were the same everywhere, how would the intensity contours look like on an isoseismal map?
- concentric circles
51
P waves travel through air, where they take the form of ___ waves.
- sound
52
In the pendulum seismograph, the pen ___.
- remains static with respect to the base
53
An isoseismal map displays contours of ____.
- intensity reported by eye witness.
54
Can you estimate the depth of the main magma chamber beneath Kilauea Volcano, Hawaii?
- 10 km
55
acceleration
- the rate of change of motion
56
aftershocks
- smaller earthquakes following a mainshock on the same section of the fault. Aftershocks can continue for years following a mainshock.
57
amplitude
- the maximum displacement above or below the undisturbed position; for example, the height of a wave crest or depth of a trough.
58
arrival time
- the time at which a seismic wave is detected by a seismograph
59
base isolation
- a system protecting buildings from earthquakes by isolating the base of the structure from the shaking ground via rollers, shock absorbers, etc.
60
body waves
- seismic waves that travels through the Earth. Primary (P) waves and secondary (S) waves are body waves.
61
creeping zone
- a section of fault where seismic energy is released frequently in small to moderate earthquakes.
62
felt area
- an area of perceptible earthquake ground motion.
63
foreshocks
- smaller earthquakes that precedes a mainshock on the same section as a fault.
64
fractures
- a general term for any breaks in rock
65
hertz (Hz)
- a unit of frequency. One hertz (Hz) equals one cycle per second.
66
inertia
- the property by which matter will remain at rest unless acted on by an external force.
67
isoseismal maps
- maps that uses contour lines to represent areas of equal Mercalli intensity.
68
liquefaction
- the temporary transformation of water-saturated loose sediment into a fluid typically caused by strong earthquake shaking
69
locked zone
- a section of a fault that has not released seismic energy for along time
70
mainshock
- the largest earthquake in a sequence.
71
megathrust earthquakes
- very large earthquakes that occur when stress accumulates at the contact between a subducting plate and overriding plate.
72
natural frequency
- the frequency at which a mechanical system (e.g. a soil, a building) vibrates when disturbed.
73
period
- the length of time for a complete cycle of waves to pass; period = 1/frequency
74
primary (P) wave
- the first seismic wave to reach a seismometer. movement is by alternating push-pull pulses that travel through solids, liquids, and gas.
75
resonance
- a vibrating body moves with maximum amplitude when the frequency of an imposed external forcing function is the same as its natural frequency
76
retrofitting
- reinforcing or strengthening an existing building or other structure.
77
secondary (S) wave
- the second seismic wave to reach a seismometer. Movement occurs by shearing particles at right angles to the directing of propogation. S waves move through solids only.
78
seism
- an earthquake
79
seismic waves
- a general term for all vibrations generated by earthquakes
80
seismic-gap method
- a theory that states that earthquakes are expected next along those fault segments that have not moved for the longest time.
81
seismograms
- the records made by a seismograph
82
seismology
- the study of earthquakes and the Earth's interior, based on the analysis of seismic data.
83
seismometers
- instruments hat detect Earth motions
84
surface waves
- seismic waves that travel along the Earth's surface only. Love and Rayleigh waves are surface waves.
GOPH 375
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