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2017/2018 > EOS 170 > Flashcards

EOS 170 Flashcards

1
Q

natural disaster

A

when a natural event causes injury, loss of life, damage to infrastructure, and/or economic losses

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2
Q

natural disasters typically caused by

A

sudden release of energy stored over a much longer time.

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3
Q

return period

A

average time between similar events at a given location

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4
Q

frequency

A

1 / period

average number of occurrences in a given time

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5
Q

magnitude

A

measure of amount of energy released

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6
Q

generally, magnitude ∝

A

frequency ^-1

inversely proportional to freq., large events less frequent

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7
Q

earthquake descriptor

A 
Great ≥8
Major 7-7.9
Strong 6-6.9
Moderate 5-5.9
Light 4-4.9
Minor 3-3.9
Very Minor 2-2.9
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8
Q

earthquake frequency (#/yr)

A 
great 1
major 10
strong 100
moderate 1000
light 10,000
minor 100,000
very minor 1,000,000
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9
Q

a natural event that is dangerous

A

hazard

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10
Q

likelihood that losses will occur

A

risk

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11
Q

vulnerability

A

exposure and susceptibility to human losses

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12
Q

Risk =

A

vulnerability X hazard

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13
Q

Hurricane Harvey

A

Houston
33 trillion gallons of water
3.1 mi^3 of water
depressed the land ca. 2cm

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14
Q

Houston vulnerability

A

built on flood plain
decreased vegetation
climate change

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15
Q

how climate change impacts hurricanes

A

increased SST –> increased storm energy

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16
Q

Hazard reduction

A

minomer

hazard = geologic phenomenon we can’t stop that, we want to reduce vulnerability

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17
Q

Irma

A

Cat5 hurricane

>200km/hr winds

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18
Q

hurricanes categorized by

A

wind speeds

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19
Q

exacerbation of forest fires

A

suppression/forest management
invasive species
climate change
human activity (campfire, cigarettes, fireworks, etc)

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20
Q

regent landslide

A

August 2017
Sierra Leone
500 killed, 600 missing
exacerbated by deforestation

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21
Q

Induced seismicity

A

earthquake triggered by humans

fluid extraction/injection increases pore fluid pressure causes faulting

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22
Q

Mexico earthquake, 2017

A 
Chiapas
M 8.1 
by triple junction
subduction eq
largest eq in 2 yrs (worldwide)
largest in mexico since 1932
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23
Q

Mexico triple junction

A

NA plate
Caribbean plate
Cocos plate

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24
Q

induced seismicity from

A

nuclear explosions
mine collapses
reservoir building drilling/frackin

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25
Q

Smallest magnitude earthquakes responsible for fatalities

A

5

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26
Q

Chiapas hazard

A

high (great earthquake) but lower than other “greats” due to deep (70km), offshore, low tsunami risk (deep),

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27
Q

magnitude scale

A

log

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28
Q

Chiapas vulnerability

A

low population
low infrastructure quality
ca. 100 deaths

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29
Q

sea-level drawback

A

hurricane winds so strong they draw the water back from the shore then after eye passes water is pushed back leading to tsunami

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30
Q

geologic hazards changing through time

A

no

weather-related hazards are increasing not geologic

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31
Q

historic costly storms

A

Hurricane Andrew 1992, 65 deaths, 26.5 billion
Katrina 2005, 1800 deaths, 108 billion
Irma 2017, 71 deaths, 70-200 billion

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32
Q

Irma records

A
  • cost
  • cat5 for 3 days, longer than any other Atl hurricane
  • accumulated storm strength (strength+duration)
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33
Q

frequency of weather-related catastrophes

A

6X the 1950s

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34
Q

earthquake fatalities per century

A

increasing- 30 eq’s causing >10,000 deaths in 20th century while only 5/cen in 1000-1700

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35
Q

why earthquake fatalities increasing

A
  • larger population
  • urbanization
  • increase in # of eq’s??
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36
Q

hugest eq risks

A

developing nation
large population
rapidly moving plates

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37
Q

Disaster management

A

After disaster: response, recovery

Before disaster: mitigation, preparedness

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38
Q

response

A

short-term
immediate
emergency workers
goal: get situation under control

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39
Q

recovery

A

mid-term
actions to rebuild community
goal: get situation back to normal

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40
Q

mitigation

A

long-term

actions to minimize harm that will take place

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41
Q

structural mitigation

A

infrastructure
retrofitting
‘earthquake-proofing’

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42
Q

examples of structural mitigation infrastructure

A

dams
dykes
floodways

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43
Q

non-structural mitigation

A 
land-use policies
building codes
public education
severe weather warnings
earthquake early warning
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44
Q

non-structural mitigation, land-use policy example

A

include green spaces in communities to decrease flooding

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45
Q

preparedness

A

steps to ensure effective response and resources when needed

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46
Q

preparedness example

A
  • stockpile essential goods and resources
  • building evac drills
  • first-aid
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47
Q

energy source for weather-related disasters

A

solar energy

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48
Q

energy source for geological disasters

A
  • Earth’s internal energy
  • Gravity
  • Impact
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49
Q

Internal E disasters

A

earthquake
tsunami
volcano

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50
Q

gravity disasters

A

land/mud slide

avalanche

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51
Q

geothermal gradient

A

25ºC / km

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52
Q

mantle temperature

A

2000-3000ºC

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53
Q

core temperature

A

4000-7000ºC

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54
Q

radius of the earth

A

6370 km

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55
Q

why is the Earth still hot

A
  • radioactive decay

- heat of formation

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56
Q

accumulation of particles into massive object via gravitational attraction

A

accretion

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57
Q

heat of formation

A

primordial heat = accretion + differentiation.

collisions generate heat

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58
Q

planetary differentiation

A

impacts - increased heat - Fe melting - melt migration to core - more heat (friction)

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59
Q

types of meteorites

A

chondrites
achondrites
stony-iron
iron

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60
Q

chondrites

A

‘stony meteorite’

  • 86% of meteorites
  • 75-90% Si minerals
  • bubbly texture (no melting)
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61
Q

importance of chondrites

A

no melting = representation of primative material (before differentiation)

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62
Q

achondrites

A

‘stony meteorite’

  • no chondrules
  • originate from outer Si mantle
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63
Q

Stony-iron meteorite

A

ca. even Si and Ni/Fe alloy

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64
Q

Pallasite

A

specific type of stony-iron meteorite representing mantle/core boundary

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65
Q

Iron meteorite

A

from large asteroid core, almost fully Ni-Fe

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66
Q

Age of Earth

A

4.56 bya

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67
Q

timing of accretion and differentiation

A

ca. 30 million year

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68
Q

radioactive decay

A

spontaneous disintegration of a nucleus w/ emission of particles and/or radiation

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69
Q

half-life

A

time for half of initial pop. of atoms to decay

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70
Q

common radioactive elements

A

U238 (t1/2 = 4.5by)
U235 (t1/2 = 0.7 by)
K40 (t1/2 = 1.3 by)
Th232 (t1/2 = 14 by)

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71
Q

heat transfer due to bulk movement of molecules w/i fluid

A

convection

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72
Q

Lord Kelvin

A

William Thompson, 1862, estimated age of E to be 100Ma assuming cooling from conduction

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73
Q

John Perry

A

Kelvins assistant, 1895, realized heat transfer was via convection, estimated E age to 2-3 Ga

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74
Q

the missing years in the age of E calculations

A

radioactivity, 1956, Marie Curie, 4.55 Ga

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75
Q

convection occurs where in earth

A

liquid outer core

solid (ductile) mantle

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76
Q

drives plate tectonics

A

convection

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77
Q

Internal heat energy responsible for

A

earthquakes
tsunami
volcanoes
mountains

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78
Q

gravity ∝

A

∝ (M1M2)/distance^2

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79
Q

kinetic energy of slides comes from

A

gravitational potential energy (stored energy)

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80
Q

conduction

A

heat transfer due to particle collision

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81
Q

solar energy reaction

A

H + H –> He + nuclear E (heat + light)

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82
Q

driving mechanism of weather and currents

A

uneven heating of earths fluids

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83
Q

why is the E still hot 4.6bya

A

convection brings heat back into core (+radioactive decay continues)

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84
Q

density of earth

A

average: 5.5g/cm^3
crust: 2-3 g/cm^3

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85
Q

how do we know E’s density

A

study gravity -> calculate volume and mass

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86
Q

Earths wobble

A

doesn’t really wobble and gravity is constant therefore uniform density distribution in concentric shells

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87
Q

solar heating drives

A

hydrologic cycle
currents
weather
climate

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88
Q

how do we know Earths structure

A
  • density distribution
  • seismic velocity distribution
  • magnetic field
  • direct observation
  • lab studies
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89
Q

seismic velocity distribution

A

seismic waves are reflected/refracted at boundaries

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90
Q

Earth’s magnetic field

A

requires convective flow of metallic fluid

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91
Q

importance of magnetic fluid

A

holds atmosphere and provides protection, ‘magnetosheath’

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92
Q

observations of Earth’s internal structure

A
  • only drill to ca. 12km

- kimberlite pipes bring deep mantle material to surface (ca. 200km)

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93
Q

lab studies of Earths structure

A
  • high T/P studies

- diamond-anvil apparatus can compress up to 200GPa equivalent to 3000km depth

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94
Q

Earth’s structure considered in terms of

A
  • chemical composition (what its made of)

- rheology (deformation under stress)

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95
Q

Stress =

A

Force/Area (N/m^2 or Pa)

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96
Q

types of stress

A

compression
tension
shear

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97
Q

compression leads to

A

contraction

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98
Q

compression

A

force inwards

perpendicular to surface

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99
Q

tension

A

force outwards perpendicular to surface

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100
Q

shear stress

A

force parallel to surface

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101
Q

tension lead to

A

extension

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102
Q

rheology of liquids

A

flow under stress

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103
Q

rheology of solids

A

elastic - recoverable deformation
ductile - permanent deformation
brittle - rigid object, fractures
plastic - high viscosity, flows

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104
Q

viscosity

A

resistance to flow

honey, brie, molasses

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105
Q

rheology depends on

A

t
T
P
compression

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106
Q

shear stress leads to

A

shearing/ destortion

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107
Q

short t, low T and/or low P =

A

possible brittle rupture

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108
Q

long t, high T and/or high P =

A

possible plastic flow

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109
Q

example of material with different rheology based on t/T/P

A

wood
bends to an extent if move slow, breaks if move fast
glaciers - flow and calve

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110
Q

crust

A
  • 0.5% of Earth mass
  • 0-1000ºC
  • density 2-3 g/cm^3
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111
Q

mantle-crust boundary

A

Mohorovicic discontinuity

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112
Q

Mantle

A 
plastic, solid, convecting
-67% of mass
-1000-3000ºC 
density 3-6 g/cm^3
-Si rock rich in Fe and Al
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113
Q

outer core

A 
liquid, convecting
30% of mass
4000ºC 
10-14 g/cm
Fluid Fe/Ni
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114
Q

Inner core

A 
solid
2% of mass
5000º
14-16g/cm^3
Fe-Ni alloy
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115
Q

basalt

A 
oceanic crust
volcanic rock
48% SiO2
3 g/cm3
ca. 10km thick
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116
Q

granitic rock

A

continental crust
60% SiO2
2.7 g/cm3
ca 35km thick

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117
Q

earths structure, compositional

A 
continental/oceanic crust
upper mantle
lower mantle
outer core
inner core
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118
Q

earths structure, rheologically

A

lithosphere
asthenosphere
mesosphere

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119
Q

lithosphere

A

crust + upper mantle = rocky, rigid

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120
Q

asthenosphere

A

weak, partial melt, flows under stress

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121
Q

T, Earths structure

A

increases nonlinearly w/ depth

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122
Q

P, earths structure

A

increases ca. linearly w/ depth (due to overburden weight)

123
Q

solid inner core vs fluid outer core due to

A

pressure

124
Q

fluid outer core vs solid mesosphere due to

A

composition

125
Q

lithosphere floats on asthenosphere at an elevation dependent on

A

thickness and density

126
Q

floating equilibrium

A

isostasy

127
Q

change in mass of floating object =

A

isostatic adjustment - change in elevation fluid

128
Q

density of water

A

1 g/cm3

129
Q

thickness of oceanic crust

A

10km

130
Q

depth of continental crust

A

ca. 35km

up to 80km

131
Q

oceanic crust sits lower in ocean than continental b/c

A

isostasy

heavier, thinner

132
Q

glacial melting =

A

isostatic rebound/ postglacial rebound

133
Q

glacial formation =

A

push crust down -> push water out of way -> uplift of adjacent crust

134
Q

Canada postglacial rebound

A

Canada raising from melting of Laurentide glacier, US moving back down

135
Q

Mexico city eq

A

M7.1
51km depth
mechanism: normal faulting
many deaths avoided due to EWS

136
Q

comparing the Mexico eq’s

A

Sep 8: M8.1, deeper, smaller population, lower vulnerability, 98 deaths
Sep 19: M7.1, shallow, higher population, high vulnerability, >250 deaths

137
Q

exacerbation of mexico eq

A

city expansion onto drained lake bed

138
Q

problems with building on drained lake beds

A

saturated sediments -> greater shaking for longer period after eq passes

139
Q

example of eq in drained lake bed city

A

Kathmandu, Nepal
in basin- greater shaking for longer
near basin - less for shorter

140
Q

liquefaction

A

saturated soil loses strength and stiffness in response to applied stress causing it to liquify

141
Q

plate deformation

A

plates are internally rigid, stress at one margin is transferred to the opposite margin, no internal deformation

142
Q

MOR

A

divergent boundary, rising mantle forms magma, cooling and solidifying forms new basaltic crus pushing plates apart, warm, low-density, topographic high

143
Q

MOR volcanism

A

decompression melting: geothermal crosses solidus resulting in partial melting

144
Q

transform boundary, transform fault

A

region where 2 oceanic plates are moving in opposite direction

145
Q

region where 1+ continental plates are moving in opposite directions

A

trans current boundary, strike-slip fault

146
Q

strike-slip fault example

A

Pacific plate ^\NA plate (San Andreas Fault)

147
Q

subduction zone

A

convergent boundary, old, cold, dense oceanic lithosphere, pulled into mantle, melting deep within mantle

148
Q

where 3 plates meet at single point

A

triple junction

149
Q

when oceanic crust is fully subjected and continental crust converges

A

continental collision zone

150
Q

results of continental collision

A

mt building, continental crust too buoyant to subduct

ex. Himalayas, Rockies

151
Q

Himalaya characteristics

A

8km above sea-level
5km average elevation
80km crustal thickness

152
Q

normal-thickness of continental crust

A

35km

153
Q

continental collision zone

A
  • wider than oceanic plate boundaries
  • form mountains
  • convergent w/ large strike-slip faults moving blocks out of way
154
Q

divergent plate boundary that forms new ocean basin

A

continental rift

155
Q

thinned edges of continent following continental rift

A

passive continental margin - not plate boundaries, separate continent and oceanic crust of same plate

156
Q

example of continental rift

A

east african rift - eastern Africa (Somalian plate) will split off of rest of Africa (Nubian plate)

157
Q

upwelling mantle plume

A

hot spot

158
Q

hot spots occur

A

anywhere (not associated w/ plate boundary)

159
Q

hot spot examples

A

Hawaii
Yellowstone
Iceland
Azores

160
Q

hot spot mechanics

A

thermal anomaly – mantle hotter than normal – geothermal crosses solidus (at depth) – plume rises

161
Q

submerged volcano

A

seamount

162
Q

Hawaiian hotspot

A

Pacific plate has moved NW over hotspot for at least 5Ma = chain of islands and seamounts

163
Q

evidence of Hawaiian hotspot

A
  • volcanic islands in line
  • oldest island (Kaua’i 5-6Ma) is farthest NW
  • islands progressively older (O’ahu 2-4Ma, Mauna Loa 0.5Ma)
164
Q

Hawaiian Island/Emperor Seamount chain

A
  • 6000km long

- kink at 43Ma (plate changed direction)

165
Q

yellowstone hot-spot track

A

NA plate moving W over hotspot

166
Q

Alfred Wegener

A

1912, proposed single supercontinent (Pangaea) and continental drift

167
Q

Pangaea ocean

A

Panthalassa

168
Q

Pangaea period

A

Jurassic

169
Q

Evidence for plate tectonics

A
  1. continents fit
  2. similar fossils on adjacent continental margins
  3. Continuities in mt ranges along cont. margins
  4. Glacial striations
  5. geomagnetic reversals
  6. earthquake locations, depths
  7. sea-floor striping
170
Q

Glacial striation plate tectonics

A
  • continents that could not be glaciated (Australia, India, SA)
  • wrong direction of movement (onto land from ocean)
171
Q

Pangaea breaks into 2 supercontinents

A

180 Ma, Jurassic

172
Q

supercontinents after Pangaea

A

Laurasia, Gondwanaland

173
Q

Future supercontinent

A

+250Ma, NA/SA collide with Africa/Eurasia

174
Q

How plate tectonics were discovered

A

WWII and cold war provided geophysical data, 1960s, Harry Hess

175
Q

John Tuzo Wilson

A

1963-1966, Canadian, described Hawaiian chain, transform faults connecting MORs

176
Q

surface elevations measured

A

satellite imagery

177
Q

NAtl begins opening

A

135Ma, early Cretaceous

178
Q

S. Atl opens, Africa reaches Europe

A

65Ma, end Cretaceous

179
Q

surface elevation distribution

A

bimodal; continental crust centred around 0km elevation, oceanic around -5km, average ca. -3km

180
Q

study of earths magnetic field through time

A

paleomagnetism

181
Q

when geographic north pole = magnetic south pole

A

reverse polarity

geomagnetic reversal

182
Q

paleomagnetism evidence

A

magnetite (Fe3O4) in basalt aligns w/ current magnetic field

183
Q

process of magnetic minerals aligning w/ magnetic field

A

thermal-remant magnetization (TRM)

184
Q

magnetic polarity scale

A

black shows normal polarity, white = reverse

185
Q

sea-floor striping

A

symmetric pattern of magnetic anomalies radiating out from MOR

186
Q

discovered, explained sea-floor striping

A

Fred Vine, Drummond Mathews, 1963

187
Q

age of oceanic lithosphere

A

all less than 300 million years old

188
Q

age of continental rocks

A

up to billions of yrs

189
Q

first earthquake detection

A

1960s, World Wide Standardized Seismograph Network (WWSSN) (to monitor nuclear explosions)

190
Q

narrow earthquake belt

A

MORs

191
Q

subduction zone earthquakes

A

Wadati-Benioff zones, unusually deep, down to 700km

192
Q

Plate tectonic forces

A
  1. Ridge push

2. Slab pull

193
Q

wide earthquake belt

A

subduction zones

194
Q

ridge push

A

upwelling mantle and gravitational collapse of young (warm, buoyant) oceanic crust at MOR

195
Q

slab-pull

A

due to old, cold, dense oceanic lithos. in subduction zone

196
Q

widest eq belts

A

continental collision

197
Q

80% of erupted magma

A

from spreading centers

198
Q

types of volcanoes

A

shield volcano

stratovolcano

199
Q

stratovolcano

A

eg. Mt Kilimanjaro, Mount Saint Helens
- layers of ash from successive flows
- common above subduction zone
- very hazardous
- ca 10% of all magma erupted
- most explosive

200
Q

Hot spot volcanism

A
  • 10% of magma erupted
  • runny lava
  • not explosive, less hazardous
201
Q

continental volcanism

A
  • explosive

eg. Yellowstone caldera-forming eruption

202
Q

Iceland

A

BOTH MOR and hotspot

  • erupts huge volumes of magma
  • decompression melting and eruption
203
Q

fault

A

planar surface of plate

204
Q

earthquakes occur

A

along faults (possibly multiple), not at a point

205
Q

slip

A

displacement of surface along fault from surface rupture

206
Q

fault planes

A

planar, striations, corrugations, indicate direction of slip

207
Q

point on fault plane where slip starts

A

hypocenter

208
Q

types of faulting

A
  • reverse
  • normal
  • strike-slip
209
Q

reverse faulting

A

‘thrust faulting’

  • horizontal convergence
  • force in, block thrust up
  • gentle dip angle ca. 30º
210
Q

strike-slip fault

A

plates move laterally past each other

211
Q

right-lateral strike slip

A

opposite block moves to the right

212
Q

graphical representation of type of faulting involved in eq

A

focal mechanism

213
Q

earthquake cycle

A

stress builds on fault – released quickly

214
Q

point directly above hypocenter

A

epicenter

215
Q

steady motion occurs pulling block away from fault but fault is ‘locked’

A

interseismic period

216
Q

normal faulting

A

horizontal extension

  • pull apart, one block slides down
  • dip angle steeper, ca. 60º
217
Q

fault rebounds causing eq

A

coseismic phase, now offset at fault

218
Q

megathrust faults

A

subduction zone, vertical and horizontal motion, stick-slip

219
Q

megathrust fault cycle

A

subducting plate gets stuck b/c cold and brittle– upper plate squeezed, bulges up – underlying plate pulls ocean down – sudden slip, rebound, overriding plate moves back down, ocean moves back up = tsunami

220
Q

elastic rebound releases

A

stored as energy as seismic waves

221
Q

2 classes of seismic waves

A

body waves

surface waves

222
Q

Body waves

A
  • move through Earth
  • P waves
  • S waves
223
Q

Surface waves

A
  • do not move through the body of Earth
  • Raleigh waves
  • Love waves
224
Q

P waves

A

compressional waves

  • primary, first to arrive
  • compress, push stationary object
  • no z direction movement, forward/back like a worm
225
Q

S waves

A

Shear waves

  • secondary
  • S-shape movement in z direction (up, down waves)
  • sheers stationary object, squishes square up into a diamond
226
Q

instrument that measures and amplifies ground motion

A

seismometer

227
Q

how seismometer works

A

attached to E, whole instrument shakes w/ E, weight does not move b/c inertia, recording device measures how far instrument moves w.r.t. mass

228
Q

distinguishing waves on a seismogram

A
  • by time of arrival

- by component of seismogram

229
Q

Raleigh wave

A
  • small waves along surface
  • up and down in z direction
  • like S wave but only at surface, not whole ‘block’
  • particles move in orbs (like ocean waves)
230
Q

records ground motion from seismometer

A

seismograph

231
Q

seismogram components

A

Horizontal (radial, transverse)
Vertical
-3 components

232
Q

Love wave

A
  • side to side waves on surface, y direction, like a snake

- move particle side to side

233
Q

seismogram

A

graphical representation of motion at a given point as a fn of t

234
Q

distinguish waves on seismogram from t

A

1st: P-waves
2nd: S-waves
3rd: Love
4th: Rayleigh

235
Q

distinguish waves on seismogram from component

A

Vertical: P-waves, Rayleigh
Horizontal transverse: Love
Horizontal radial: S-waves, Rayleigh

236
Q

largest amplitude waves

A

surface (most damaging)

237
Q

slower waves

A
  • surface (arrive later) slower than body

- s slower than p

238
Q

seismic waves that travel through liquid (outer core)

A

P-waves

239
Q

how we determine interior structure of E

A

refraction, reflection of body waves by major boundaries in E (shadow zones)

240
Q

further seismic stations

A

record P and S as farther apart b/c P travelling faster

241
Q

distance btw earthquake and seismometer

A 
Ts = x/Vs; Tp=x/Vp
x = VpVs(Ts-Tp)/(Vp - Vs)
242
Q

pinpointing eq epicenter

A

determine distance from eq to seismometer for 3 locations, plot them, where they cross

243
Q

Eq Early Warning system

A
  • seismometer detects p-waves
  • calculate magnitude and distance, expected intensity and arrival t
  • send warning to city
  • time to get outside before surface waves hit
244
Q

determining magnitude

A
  • observed seismic waves
  • correct for distance
  • cross plot distance, magnitude, amplitude
245
Q

moment (Nm)

A

eq rupture area (m^2) x amount of displacement (m) x Shear modulus (Nm^-2)

  • rupture area = rupture length x width
  • shear modules = resistance to deformation by shear stress
246
Q

exploring magnitude equation

A
  • fault area and displacement highly correlated
  • rupture area KEY to magnitude
  • large eq’s rupture large faults (subduction zone)
247
Q

subduction zone eq’s

A

megathrust

  • gently-dipping interface of thrust fault + long = large SA
  • can generate large tsunami
  • 17/20 largest eq’s since 1900 were megathrust
248
Q

major west coast fault zones

A

San Andreas Fault (SAF)

Cascadia Subduction Zone (CAS)

249
Q

which major west coast fault zone is likely to produce a larger eq

A

CAS - subduction zone, larger SA

250
Q

an increase in M of 1 unit =

A
  • 30X increase in E

- 10X reduction in frequency

251
Q

M =3, E equivalent to

A
  • World’s largest nuclear test

- Mt. St Helen eruption

252
Q

M = 6, E equivalent

A

Hiroshima atomic bomb

253
Q

global cumulative seismic moment release

A
  • dominated by megathrusts

- 5 >9.0 megathrusts = more than 1/2 of moment released from 1900-2014

254
Q

entire length of Pacific ring of fire subduction zone

A

30,000 km

255
Q

max slip ever observed

A

50m

256
Q

max magnitude eq

A

10.5 if every subduction zone in the world erupted at once

257
Q

max realistic earthquake

A

entire Aleutian trench (between Asia and NA) or Peru-Chile trench = M9.9

258
Q

describing earthquakes by felt intensity

A

Mercalli Scale
-instrumental, weak, slight, moderate, rather strong, strong, very strong, destructive, violent, intense, extreme, cataclysmic (12)

259
Q

Isoseismal map

A

concentric contours of equal seismic intensity focused on approximate epicentre

260
Q

isoseismal map bias

A
  • proximity of eq to population centre

- personal account exaggeration

261
Q

what governs felt intensity

A
  • magnitude
  • distance from eq
  • depth of eq
  • infrastructure height, quality
  • earth surface
262
Q

Similar magnitude different intensity

A

M5.8 Mineral, VA
M6.5 San Simeon, Ca
felt much further away in VA due to bedrock geology, easily felt 1000km away

263
Q

why eq felt further away in Eastern US

A

less tectonics = less broken up plates = less dissipation/attenuation of seismic energy

264
Q

Intensity of eq’s with same magnitude, different depth

A

M6.5 San Simeon, CA, 7km
M6.3 New Zealand 163 km
NZ = barely any reports of people feeling it

265
Q

MOR earthquakes

A
  • normal faulting
  • young, warm, thin ocean crust
  • eq’s generally small
266
Q

Transform fault eq

A
  • strike-slip faulting
  • older, colder, thicker crust than MOR
  • larger magnitude than MOR
267
Q

part of uppermost crust brittle enough to host earthquakes

A

seismogenic layer

268
Q

transform fault

A

adjacent plates are moving in opposite direction

269
Q

fracture zone

A

adjacent plates are moving in same direction = no faulting = no earthquake

270
Q

Earthquakes that occur at subduction zones

A

crustal eq (small), megathrust (large), intermediate eq, deep eq, outer rise normal fault eq

271
Q

outer rise normal faulting eq

A

few, large, where incoming oceanic plate begins to flex

-not very hazardous due to proximity (at MOR)

272
Q

deep earthquakes

A
  • up to 700im
  • only in subduction zones w/ rapidly descending plate
  • usually too far to be dangerous
273
Q

why do deep eq’s only occur if plate is descending rapidly

A

so it stays cold and brittle, if it subduct slowly it will warm up and lose brittle nature needed to conduct eq

274
Q

Intermediate earthquakes

A

50-300 km

  • in all subduction zones
  • can be very dangerous
  • intraslab, within subducting slab
275
Q

what type of earthquakes were the Mexico quakes?

A

subduction zone, intermediate

-top of subducting Cocos plate

276
Q

classes of hazardous earthquakes in Cascadia

A
  1. Intermediate/ intraslab
  2. megathrust
  3. crustal
277
Q

Intermediate eq example

A

Nisqually WA, 2001, hypocenter 57km depth, 1 death, 1-4billion in damages

278
Q

Cascadia’s last megathrust

A

1700AD

279
Q

Cascadia megathrust max size, recurrence

A

M9, 500-600yr

280
Q

deep JDF plate max eq and recurrence

A

M7+, 30-50yr

281
Q

West coast crustal quake max size and recurrence

A

M7+, hundreds of years?

282
Q

Crustal earthquakes

A

-moderate magnitude
-could be close to pop centre
-

283
Q

VI crustal fault

A

Leech River fault

-right across southern tip of island

284
Q

airborne laser mapping that penetrates forest canopy to determine surface topography

A

lidar

285
Q

continental plate boundary earthquakes

A

shallow, potentially close to populations

  • broken up crust, no megathrust
  • seismogenic layer ca. 15km
  • M7-8
  • mostly along collision zone
286
Q

continental plate boundary example

A

Bam, between two deserts

  • half of pop lost due to poor infrastructure (adobe)
  • eq rupture along escarpment Bam-Baravat ridge
287
Q

Why Bam is an oasis

A
  • ridge = impermeable, dam on water table

- build tunnels to tap water source, irrigate crops

288
Q

the bittersweet side of Iran faults

A
  • water sources

- active faults!

289
Q

Tehran

A

continental plate boundary

  • pop. 14 million
  • destroyed by 4 past eps
  • city centre right next to Alborz mountains
290
Q

continental plate deaths

A

more than subduction zones even though smaller magnitude

291
Q

intraplate earthquakes

A
  • unusual, infrequent
  • hazardous
  • b/c plates are not perfectly rigid
  • variety of faulting mechanisms
292
Q

Intraplate seismicity in eastern Canada associated with

A

-passive continental margins
or
-ancient failed rifts

293
Q

passive continental margin

A
  • edge of continent

- btw continent, ocean on SAME plate

294
Q

failed rifts, Canada

A

from formation of Atlantic (branches that failed)

eg. Labrador Sea

295
Q

intraplate earthquake stresses

A
  1. Plate tectonic stress
  2. postglacial rebound
  3. Manmade stresses
296
Q

Plate tectonic stresses on intraplate

A

ridge/push, slab/pull stresses generated through interior of plate

297
Q

Postglacial rebound, intraplate earthquake example

A

-Parvie fault scarp, Sweden
M8, 10ka
-1989 M6 Ungava, Quebec

298
Q

Induced intraplate eq example

A

Oklahoma, Colorado, Texas, Alberta, N BC

299
Q

building to resist earthquakes

A
  1. Make building resistant to horizontal movement
  2. Make resistant to stress
  3. reduce resonance
  4. base isolation
300
Q

how to make buildings resistant to horizontal shearing

A

braces, brackets, shear walls, bolts

301
Q

how to make buildings resistant to stress

A

Wood - flexible, light, elastic

Steel - strong, ductile

302
Q

reducing resonance

A

depends on size, substrate (bedrock/sediment), weight distribution, shape, building material, foundation

303
Q

Resonance rule of thumb

A

buildings sway at resonant frequency 10 Hz / # of stories

304
Q

base isolation

A
  • ball bearings, wheels, shortchanged absorbers

- Qube, Vancouver hangs from central vertical support to majority of building is free of the ground

2017/2018 (7 decks)

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