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College Geology > Lesson 14 Earthquakes > Flashcards

Lesson 14 Earthquakes Flashcards

1
Q

This energy, which takes the form of waves, radiates in ____ directions from the earthquake’s source, called the focus.

A

all

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2
Q

why do rocks rupture creating volcanoes?

A

they have been subjected to stresses beyond their limit

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3
Q

What movements are earthquakes associated with?

A

movements along faults

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4
Q

Movements along faults are explained by __________

A

the plate tectonics theory

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5
Q

Mechanism for earthquakes was first explained by ____

A

H. Reid

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6
Q

Rocks “spring back” is a phenomena called _____

A

elastic rebound

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7
Q

What is the theory that the Earth’s outer shell is divided into several plates that glide over the mantle?

A

plate tectonics theory

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8
Q

Vibrations (earthquakes) occur as_______ returns to its original shape?

A

rock elastically

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9
Q

The movements that produce most earthquakes occur along large fractures, called ______?

A

faults

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10
Q

What is the earthquake’s source called?

A

focus

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11
Q

Aseismic fault slip that occurs in the uppermost part of the earth’s crust during the time between large stress-releasing earthquakes or as “afterslip” in the days to years following an earthquake.

A

Fault creep

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12
Q

What often follows earthquakes?

A

aftershocks

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13
Q

What often precedes earthquakes?

A

foreshocks

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14
Q

What is the study of earthquake waves?

A

seismology

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15
Q

What is a earthquake recording instrument ?

A

seismograph

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16
Q

What does a seismograph record?

A

movements of earth

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17
Q

What is the record recorded by the seismograph called?

A

seismogram

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18
Q

What are the two main groups of seismic waves generated during an earthquake?

A

surface waves

body waves

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19
Q

What does P waves stand for?

A

primary waves

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20
Q

What does S waves stand for?

A

secondary waves

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21
Q

Which wave has the slowest velocity?

A

Surface waves

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22
Q

Which wave has a complex motion?

A

Surface waves

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23
Q

Which wave “shakes” the particles in rock at right angles to their direction of travel?

A

S waves

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24
Q

Which wave push (compress) and pull (dilate) rocks in the direction the wave is traveling?

A

P waves

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25
Q

What can S waves travel through?

A

Solids

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26
Q

What can P waves travel through?

A

Solids
Liquids
Gases

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27
Q

Which wave travels along the outer layer of Earth?

A

Surface waves

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28
Q

Which wave travels through Earth’s interior?

A

Body waves

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29
Q

In solid material, how much faster does the one body wave travel than the other?

A

P waves travel 1.7 times faster than S waves

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30
Q

Name the waves from slowest to fastest velocity?

A

Surface waves
S waves
P waves

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31
Q

What is the order that the waves occur?

A

P waves
S waves
Surface waves

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32
Q

What wave is the most destructive?

A

Surface Waves

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33
Q

The place within Earth where earthquake waves originate?

A

focus

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34
Q

Point on the surface, directly above the focus?

A

Epicenter

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35
Q

How is the epicenter located?

A

determined using the difference in velocities of P and S waves

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36
Q

List three examples of Earthquake zones being closely correlated to plate boundaries?

A

Circum-Pacific belt (ring of fire)
Oceanic ridge system (splits Atlantic in half)
Mediterranean-Asiatic belt

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37
Q

How many station recordings are needed to locate an epicenter?

A

three

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38
Q

To find an epicenter, a _____ is drawn around each of the 3 stations equal to the ______distance.
The point where they _____is the epicenter.

A

circle
epicenter
intersect

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39
Q

The principal earthquake epicenter zones through the world’s oceans?

A

Oceanic ridge system (splits Atlantic in half)

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40
Q

The principal earthquake epicenter zones along the outer margin of the pacific ocean ?

A

Circum-Pacific belt (ring of fire)

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41
Q

A measure of the degree of ground shaking at a given locale based on the amount of damage?

A

Intensity

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42
Q

What is most often used to measure intensity of an earthquake?

A

Modified Mercalli Intensity Scale

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43
Q

What are the two fundamentally different measures that seismologists use to describe the size of an earthquake?

A

intensity and magnitude

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44
Q

The Modified Mercalli Intensity Scale uses damage to _______ to estimate the intensity of ground shaking for a local earthquake.
for example: in ______

A

buildings

california

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45
Q

Magnitude is calculated from seismic records and estimates the amount of energy _______ of an earthquake.

A

released at the source

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46
Q

Who introduced the concept of magnitude?

A

Charles Richter

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47
Q

What is used to express magnitude?

A tenfold increase in ground shaking corresponds to an increase of ___on the magnitude scale.

A

logarithmic scale

one

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48
Q

How is magnitude often measured?

A

using the Richter scale

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49
Q

What is the Richter scale based on?

A

amplitude (maximum displacement) of the largest seismic wave

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50
Q

Each unit of Richter magnitude equates to roughly a ____-fold energy increase?

A

32

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51
Q

Does the Richter scale estimate adequately for very large earthquakes as well?

A

no

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52
Q

What is currently used to estimate the size of moderate and large earthquakes?

A

Moment magnitude

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53
Q

What 3 things are used to calculate the moment magnitude scale ?

A

Average displacement of the fault
Area of the fault surface
Strength of the faulted rock

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54
Q

The 2 most obvious factors that determine the amount of destruction accompanying an earthquake ?

A

magnitude

proximity to a populated area

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55
Q

Name 5 secondary effects of earthquakes ?

A 
Tsunamis
Seismic sea waves
Landslides
Ground subsidence
Fire
56
Q

What are the factors that determine structural damage?

A

Intensity
Duration of vibrations
Nature of the material upon which the structure rests
The design of the structure

57
Q

What can happen from the ground because of the quake?

A

Liquefaction

58
Q

During liquefaction, _______material turns fluid and

underground objects may _______?

A

saturated

float to surface

59
Q

Long-range forecasts are based on the premise that earthquakes are ______.

A

repetitive or cyclical

60
Q

Substantial research to predict earthquakes is underway in countries where earthquake risk is ____.

A

high

61
Q

Seismologists study the _______ of earthquakes for patterns, so their occurrences might be predicted.

A

history

62
Q

Can seismologists predict short range or long range earthquakes?

A

long range

63
Q

What is given when seismologists predict a quake?

A

a probability

64
Q

What are the four major zones of Earth’s interior?

A

crust
mantle
outer core
inner core

65
Q

Where does most of our knowledge of Earth’s interior come from?

A

study of P and S waves

66
Q

Earth interior can be examined from the ______of P and S waves through earth depending on properties of the ______

A

travel times

minerals

67
Q

Earth interior can be examined from the fact that s waves only go through _____

A

solids

68
Q

What are the layers confined by?

A

composition

69
Q

What layer of earth is a thin, rocky outer layer?

A

crust

70
Q

Does the crust vary in thickness?

A

yes

71
Q

How thick is the crust in oceanic regions?

A

about 7 km (5 miles)

72
Q

How thick can the crust exceed in some mountainous regions?

A

70 km (40 miles)

73
Q

How thick is the continental crust?

A

averages 35-40 km (25 miles)

74
Q

What are the two parts of the crust?

A

Continental crust

Oceanic crust

75
Q

What is the average density of continental crust?

A

2.7 g/cm3

76
Q

What is the upper continental crust composed of ?

A

granitic rocks

77
Q

What is the lower continental crust composed of ?

A

akin to basalt

78
Q

How old is the continental crust?

A

4 billion years

79
Q

How old is the oceanic crust?

A

180 million years younger than the continental crust

80
Q

What is the composition of oceanic crust?

A

basaltic composition

81
Q

What is the density of oceanic crust?

A

3.0 g/cm3

82
Q

Where is the mantle located?

A

below the crust

83
Q

What is the thickness or depth of the the mantle?

A

2900 km

1800 miles

84
Q

What is the composition of the uppermost mantle? igneous rock peridotite

A

igneous rock peridotite

85
Q

Does the mantle composition change with more depth?

A

yes

86
Q

What is the radius of the outer core?

A

3486 km (2161 miles)

87
Q

What is the average density of the outer core?

A

11 g/cm3

88
Q

What is the outer core composed of?

A

iron-nickel alloy

89
Q

What is the location and shape of the outer core?

A

below mantle

sphere

90
Q

What characteristic does the outer core exhibit?

A

characteristics of a mobile liquid

91
Q

How thick is the outer core?

A

2270 km

92
Q

What is the radius of the inner core?

A

about 1216 kilometers

93
Q

What is the inner core?

A

a solid metallic sphere

94
Q

What are the three layers defined by physical properties?

A

Lithosphere
Asthenosphere
Mesosphere (or lower mantle)

95
Q

Describe the temp., texture, and state of the lithosphere?

A

Cool, rigid, solid

96
Q

What is the lithosphere consist of?

A

Crust and uppermost mantle

97
Q

How thick is the lithosphere?

A

100 km thick

98
Q

What is the depth of the asthenosphere?

A

660 kilometers

99
Q

Where is the asthenosphere located?

A

beneath the lithosphere

upper mantle

100
Q

Describe the texture of the asthenosphere?

A

soft, weak layer

easily deformed

101
Q

The crust and uppermost mantle form Earth’s cool rigid outer shell called ?

A

lithosphere

102
Q

Beneath the lithosphere lies a soft, relatively weak layer of the mantle known as the ?

A

asthenosphere

103
Q

________ rocks such as _______ are thought to make up the mantle.

A

ultramafic

peridotite

104
Q

What two elements is the core mainly composed of?

A

iron and nickel

105
Q

What is the temperature of rocks in the mesosphere?

A

very hot

106
Q

Where is the mesosphere located?

A

lower mantle

107
Q

How many kilometers deep can the mesosphere be?

A

660-2900 km

108
Q

What is the texture of the mesosphere?

A

more rigid layer

109
Q

What is the flow of the rocks in the mesosphere?

A

capable of gradual flow

110
Q

What in the outer core is responsible for the earth magnetic field?

A

convective flow of metallic iron

111
Q

What state is the outer core?

A

liquid layer

112
Q

How thick is the outer core?

A

2270 km (1410 miles)

113
Q

Which layer generates earths magnetic field?

A

outer core

114
Q

What is the radius of the inner core?

A

1216 km (754 miles)

115
Q

What state does the inner core behave like?

A

solid

116
Q

What shape is the inner core?

A

sphere

117
Q

Mohorovicic discontinuity shows that the velocity of seismic waves _______ abruptly below ___ km of depth

A

increases

50

118
Q

What does Mohorovicic discontinuity separate?

A

crust from underlying mantle

119
Q

What says the velocity of seismic waves increases abruptly below 50 km of depth?

A

Mohorovicic discontinuity

120
Q

How was earths major layers discovered?

A

using changes in seismic wave velocity (Mohorovicic discontinuity)

121
Q

Absence of P waves from about 105 degrees to 140 degrees around the globe from an earthquake?

A

shadow zone

122
Q

What explained if Earth contained a core composed of materials unlike the overlying mantle?

A

shadow zone

123
Q

A shadow zone is the absence of ______from about ____ degrees to _____degrees around the globe from an earthquake?

A

p waves
105
140

124
Q

What did shadow zones explain?

A

if Earths core had materials unlike the mantle

125
Q

The size of the inner core was calculated using _____from _______generated during _______ _____tests

A

echos
seismic waves
underground nuclear

126
Q

The inner core was discovered by noting a ______ of _____ within the ____?

A

new region
seismic reflection
core

127
Q

What was the only thing scientists had to determine the oceanic crust composition prior to the 1960s?

A

seismic evidence

128
Q

What made the recovery of ocean floor samples possible?

A

deep-sea drilling technology

129
Q

It was found that mantle composition is more ________

A

speculative

130
Q

Mantle Lava from the asthenosphere has a composition similar to that which results from the partial melting of a rock called _____

A

peridotite

131
Q

Where does evidence of a core come from?

A

meteorites

132
Q

What explaines earths density best?

A

an iron core

133
Q

What concept does earths magnetic field support?

A

molten outer core

134
Q

The core got its composition because ___, and other dense metals _____ to earth interior during the planets early history.

A

iron

sank

135
Q

What is the range of the meteorite compositions, proving a core?

A

from metallic to stony

136
Q

What are metallic meteorites made of?

A

iron and nickel

137
Q

What are stony meteorites composed of?

A

dense rock similar to peridotite

College Geology (14 decks)

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