EES 150 Exam 2 Flashcards
(141 cards)
1
Q
What’s an earthquake?
A
A shaking of Earth’s crust due to a release of energy
2
Q
What do earthquakes create?
A
Seismic waves
3
Q
What can cause an earthquakes?
A
.Volcanic activity
.Meteorite impact
.Underwater landslides
.Nuclear bomb explosions
4
Q
What is the most frequent cause of earthquakes?
A
Movement along faults
5
Q
Do earthquakes or buildings kill people?
A
Buildings
6
Q
How do the earthquakes in Japan differ from Haiti?
A
Some of them are deeper
7
Q
What produces a tsunami?
A
The offset of the ocean floor displaced water
8
Q
Why does Japan experience a lot of earthquakes?
A
A subduction zone
9
Q
What caused many people to die in Japan?
A
Tsunami and powerful earthquake
10
Q
What caused many people to die in Haiti?
A
Poor building codes and a large earthquake
11
Q
Why does Haiti experience a lot of earthquakes?
A
Because it’s along a transform plate boundary in the Caribbean.
12
Q
What’s stress?
A
A force applied to a rock
13
Q
What’s strain?
A
The response to the stress
14
Q
What’s brittle deformation?
A
When a rock breaks
15
Q
What’s ductile deformation?
A
When a rock bends/ change shape
16
Q
What’s evidence of brittle deformation?
A
A fault
17
Q
What is evidence of ductile deformation?
A
A fold
18
Q
When do earthquakes occur?
A
When rocks in the Earth’s crust behave in a brittle fashion, break and move relative to each other
19
Q
What are 2 types of stresses of rocks?
A
Uniform pressure
Differential pressure
20
Q
What the 3 types of differential stress?
A
Compression
Extension
Shear
21
Q
What plate boundary causes compression?
A
Convergent
22
Q
What plate boundary causes extension?
A
Divergent
23
Q
What plate boundary causes shear?
A
Transform
24
Q
What terms do geologist use to describe rock layers and fault orientation?
A
Strike and dip
25
What's a strike?
The line formed by the intersection of the inclined plane with a horizontal one
26
What's a dip?
The direction of inclination
27
What's the difference between a strike-slip fault & a dip-slip fault?
Strike-slip fault: Moves back and forth
| Dip-slip faulty: Moves up and down
28
How do you interpret dip-slip faults?
1. Determine which side went up
| 2. Determine which side is the hanging wall
29
How can you classify faults?
By the relative movement along them
30
What's an oblique fault?
A fault that involves both kinds of movement
31
What's elastic rebound?
A pre-earthquake strain and/ or an earthquake strain
32
How does a pre-earthquake strain describe movement along a fault?
A gradual strain in space and time
33
How does a pre-earthquake strain describe movement along a fault?
An abrupt strain in space and time
34
Are shallow faults locked or transitioned and caused by what
lock and earthquakes
35
Are deeper faults locked or transitioned and caused by what
Transition and tremor and slip
36
What's a faults hypocenter (focus)?
The exact location of the earthquake
37
What's the faults
| epicenter?
The location directly above on the surface
38
What are primary waves?
Compressional earthquake waves that travel the fastest
39
How do P waves travel?
They compress and expand as they move back and forth
40
Can S waves move through liquid? Why?
No, because liquids don't move up and down relative to each other
41
How do S-waves travel?
They move up and down relative to each other and shear at right angles
42
What's used to record earthquakes?
Seismographs
43
What are seismograms generated by?
Earthquakes, although from nuclear testing
44
When do you measure the S waves?
Before the amplitude increases
45
How many seismograms are needed to determine the epicenter?
3
46
When is a station the closet?
When the distance between the P and S wave isn't far
47
What 3 components are used to measure all directions?
.E-W
.N-S
.Vertical
48
How do waves travel within the Earth?
More rapidly at depth where material is more dense
49
What's a S-wave shadow zone?
S-waves being detected to only 103 degrees on either side of the earthquakes
50
What's a P-wave shadow zone?
A refraction at the core-mantle and inner core/ outer core
51
What do seismic tomographs show?
Cool, subducted lithospheric plates
52
What's the difference between cool and warm areas?
.Cool- high velocity
| .Warm-low velocity
53
How many people generally are killed by earthquakes each year?
Thousands
54
What are some factors that influence whether an earthquake will kill large numbers of people?
Buildings
| Tectonic plates
55
What's the difference between Japan's and Haiti's tectonic setting?
Japan: Continental-Oceanic convergent boundary
Haiti: Continental-Continental transform boundary
56
Are large earthquakes frequent occurrences?
No
57
What effect(s) does stress have on rocks?
Breaking or bending/ changing a rocks formation
58
What can strain be?
Change in size, shapes, or volume
59
What's a fold?
A structure caused by ductile deformation
60
What's a fault?
A structure caused by brittle deformation
61
What's differential stress?
Stress where there's more forces pressed on the sides of the rock, compressing the rock
62
What are 2 kinds of dip-slip faults?
Normal and reverse
63
What's the difference between a normal and reverse dip-slip fault?
Normal: has a zone of omission and hanging wall moves down
Reverse: has of zone of repetition and hanging wall moves up
64
What's the difference between the hanging wall and foot wall?
Hanging wall is on the right
| Footwall is on the left
65
What kind of differential stress causes reverse dip-slip faults?
Compression
66
What kind of differential stress causes normal dip-slip faults?
Extension
67
What are two kinds of strike-slip faults?
Right and left lateral
68
What differential stress causes strike-slip faults movement?
Shear
69
How can movement along strike-slip faults cause compression?
When a left-stepping right-lateral strike-slip fault results in compression and uplifting
70
How can movement along strike-slip faults cause extension?
When a right-stepping right-lateral strike-slip fault results in rifting and the formation of basins
71
What's an episodic tremor and slip?
A seismic phenomenon observed in subduction zones that's a non-earthquake seismic rumbling, tremor, and slow slip along the plate interface
72
How can you tell the difference between an earthquake and tremor & slip?
By the speed and focus.
Tremor and Slips have a slow slip
Earthquakes have a fast slip
73
How does a fault move due to elastic rebound?
It moves fast
74
How does episodic tremor and slip differ from our classic view of fault movement?
It moves slower and take days
75
What kind of waves are generated from earthquakes?
P,S, and Surface waves
76
What are secondary waves (S-waves)?
Shear earthquake waves at right angles to the wave direction that travel slower than P-waves
77
What are surface waves and how do they travel?
Slow earthquake waves whose effect lessens with depth. Slow and on the surface
78
Why does a seismograph have 3 components?
To measure all direction of ground movement.
79
How can we use P & S wave travel times to calculate the distance to the earthquake?
By finding a point where the waves intercept each other at 3 different locations
80
What's the S-wave shadow zone?
A zone where S-waves can only be detected 103 degrees to either side of earthquakes and creates a liquid layer
81
How do earthquakes help us understand Earth's interior?
By how waves are refracted as they encounter boundaries between 2 types of material and traveling more rapidly at depth where material is more dense
82
What's the P-wave shadow zone?
A zone where P-waves extend from 103-143 degrees away from the earthquake
83
Where are P-waves refracted?
The core-mantle and the inner/outer core, suggesting the presence of the solid inner core
84
What's a seismic tomograph?
A 3-D image of Earth's sub-surface characteristics in an effort to understand deep geological structure by gathering P and S waves travel time measurements.
85
How does seismic tomograph help us understand the nature of the mantle?
That the in cool areas of the mantle there's high velocity and warm areas in the mantle there's low velocity
86
What's the difference between warm in cool areas in the mantle?
Cool areas: Mantle plumes
| Warm areas: Subduction zones
87
How does the effects of ground motion vary?
By local geology, distance from earthquake, and local building codes
88
What's sediment liquefaction?
When the sediment or soil is saturated with water
89
What areas are vulnerable to sediment liquefaction?
Areas with loose sediment and near bodies of water
90
What's a fault scarp?
Changes in ground level are caused by movement along faults during earthquakes where one side is taller than the other
91
How are landslides & avalanches associated with earthquakes?
They can be set off by earthquake waves in areas of steep slopes
92
How are tsunamis associated with earthquakes?
If land slides into the ocean, the displaced water will form a tsunami wave
93
What are some secondary dangers of earthquakes?
```
Damaged roads
Fire
Broken levees
Broken pipelines
Power grid problems
```
94
What's the difference between magnitude and intensity?
Magnitude does not vary by location
| Intensity does
95
What's magnitude?
A measurement of some parameter of an earthquake
96
What's intensity?
Is how it affects people
97
What's the Richter scale?
A magnitude scale based on amplitude of earthquake waves
98
How is the Richter scale calculated?
By the distance between S & P waves and amplitude
99
what factors are considered when calculation the magnitude of an earthquake based on "seismic moment"?
Area of fault rupture
Amount of displacement
Force needed to cause rocks to displace
100
What is the Moment Magnitude Scale?
A magnitude Scale based on "Seismic moment"
101
What are the advantages of using the moment magnitude scale?
It's more accurate for large earthquakes which gives a larger number
102
What's the Mercalli scale?
A scale that describes earthquake intensity
103
How is the Mercalli scale used?
It has a chart that has 3 column; intensity, shaking, and description/damage
104
What causes Mercalli intensity to vary?
Distance from epicenter
105
What's a shake map?
A map that uses color to denote mercalli intensity
106
What causes tsunamis to form?
Earthquakes, volcanic activity, and landslides
107
Which is more likely to cause massive numbers of deaths, an earthquakes or tsunami?
Tsunami
108
What caused the 2004 Banda Aceh tsunami?
An earthquake
109
How is the Banda Aceh tsunami related to plate tectonics?
It happened along a subduction zone, dragged the overriding plate with it, and then rebounded back
110
What's the DART system?
A system that tracks tsunamis by monitoring water pressure on the ocean floor.
111
What are 2 ways volcanoes and tsunamis are linked?
1. Tsunamis may be caused by volcanic eruptions- lava may displace seawater
2. Volcanic islands are prone to underwater landslides
112
How did the eruption of Krakatau cause a tsunami?
By the collapse of the volcano into its magma chamber
113
Why are the shores of volcanic islands especially prone to landslides?
Because lava cools quickly when it meets cold seawater, leading to the buildup of steep slopes and eventually collapse
114
How does the shores of volcanic islands trigger tsunamis?
By the collapse of the lava deltas in the sea
115
What tsunami threat exists for the Atlantic?
The eruption of the volcano of Cumbre Vieja
116
What is the geologic explanation for the tsunami threat for the Atlantic?
Waves as high as 13m high on the eastern US coast
117
Why is Hawaii especially threatened by tsunamis?
Because it's surround by the "ring of fire" and threated from all directions
118
How doe tsunami waves interact with islands (as opposed to wind-generated waves)?
Wind-blown waves have short wavelengths & generally affect only of side of an island and ripples to many islands until the waves stop on their own
119
How does the shape of the ocean basin and water depth affect the movement of the tsunami wave?
The waves do not travel outward in all directions equally
120
Why does the west coast of the US have a lot of earthquakes?
Because it's near subduction zones, transform faults, and mid-ocean ridges
121
How did the San Andreas fault form?
By the subduction of an oceanic plate over several 10's of million of years. (Farallon plate)
122
What caused the Good Friday earthquake in Alaska?
Vertical displacement associated with a subduction zone
123
Why are there earthquakes along the Cascadia subduction zone?
Because of the subduction of the Juan de Fuca at around 4.5 cm/yr
124
How do we know there was a very large earthquake in Cascadia in 1700?
By the subsidence of land killing of coastal trees , rupture zone, fire pits, and tree ring dating
125
Why do we think the earthquake in Cascadia was a magnitude 9?
Eyewitness accounts of intensity from the oral records of First people
126
Why do we compare the Cascadia earthquake with the one in Chile?
Related to subduction and the largest recorded earthquakes
127
What part of Kentucky is given a high seismic risk and why?
Western Kentucky and because of large earthquakes that happened in 1811-1812
128
What were the effects of the 1811-1812 New Madrid earthquake?
Ground displacement, new lakes, cliffs formed, waterfalls formed in streams, and sand blows
129
What are some ways the magnitudes of the New Madrid earthquakes were calculated and why do they give different results?
1. Fault-rupture length estimates from aftershock location give smaller moment magnitudes: 7.3-7.7
2. Soft, water-saturated sediment of ground amplifies shaking: 7.0 to 7.5
130
Why do earthquakes occur in the New Madrid area?
Because of "Reelfoot Rift"
131
What's the reelfoot rift?
A buried ancient failed rift valley that formed ~ 600 million years ago
132
How did the reelfoot rift probably form?
By aulacogen( failed rifts, often form as continents break apart)
133
What's a shake map?
A map that uses color to denote Mercalli intensity
134
What are some reason building collapse during earthquakes?
Soft first floors and hollow core brick construction
135
Does the Mercalli intensity vary with distance from epicenter?
Yes
136
How does the time of day influence the death rate when an earthquake occurs?
Some people may start their day and go to work at certain times and some people stay at home at certain times
137
How does paleoseismology help us understand earthquake risk?
It's the study of ancient earthquakes to help understand earthquake frequency and plan for the future
138
What's resonance?
Is when the building period and the earthquake wave period match and combine, increasing shaking
139
What happens to earthquake waves when they pass through loose sediments?
They travel more slowly
140
What are some ways to decrease the effects of resonance?
Change of shape & height of building. Move weights to lower floors and building materials.
141
What are some engineering techniques to help buildings withstand earthquakes?
Interior walls especially shear walls, flexible bracing frames, base isolation (shock absorbers), small frame construction, not too tall, modern construction
