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EOS 170 Flashcards

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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
Smallest magnitude earthquakes responsible for fatalities
5
26
Chiapas hazard
high (great earthquake) but lower than other "greats" due to deep (70km), offshore, low tsunami risk (deep),
27
magnitude scale
log
28
Chiapas vulnerability
low population low infrastructure quality ca. 100 deaths
29
sea-level drawback
hurricane winds so strong they draw the water back from the shore then after eye passes water is pushed back leading to tsunami
30
geologic hazards changing through time
no | weather-related hazards are increasing not geologic
31
historic costly storms
Hurricane Andrew 1992, 65 deaths, 26.5 billion Katrina 2005, 1800 deaths, 108 billion Irma 2017, 71 deaths, 70-200 billion
32
Irma records
- cost - cat5 for 3 days, longer than any other Atl hurricane - accumulated storm strength (strength+duration)
33
frequency of weather-related catastrophes
6X the 1950s
34
earthquake fatalities per century
increasing- 30 eq's causing >10,000 deaths in 20th century while only 5/cen in 1000-1700
35
why earthquake fatalities increasing
- larger population - urbanization - increase in # of eq's??
36
hugest eq risks
developing nation large population rapidly moving plates
37
Disaster management
After disaster: response, recovery | Before disaster: mitigation, preparedness
38
response
short-term immediate emergency workers goal: get situation under control
39
recovery
mid-term actions to rebuild community goal: get situation back to normal
40
mitigation
long-term | actions to minimize harm that will take place
41
structural mitigation
infrastructure retrofitting 'earthquake-proofing'
42
examples of structural mitigation infrastructure
dams dykes floodways
43
non-structural mitigation
``` land-use policies building codes public education severe weather warnings earthquake early warning ```
44
non-structural mitigation, land-use policy example
include green spaces in communities to decrease flooding
45
preparedness
steps to ensure effective response and resources when needed
46
preparedness example
- stockpile essential goods and resources - building evac drills - first-aid
47
energy source for weather-related disasters
solar energy
48
energy source for geological disasters
- Earth's internal energy - Gravity - Impact
49
Internal E disasters
earthquake tsunami volcano
50
gravity disasters
land/mud slide | avalanche
51
geothermal gradient
25ºC / km
52
mantle temperature
2000-3000ºC
53
core temperature
4000-7000ºC
54
radius of the earth
6370 km
55
why is the Earth still hot
- radioactive decay | - heat of formation
56
accumulation of particles into massive object via gravitational attraction
accretion
57
heat of formation
primordial heat = accretion + differentiation. | collisions generate heat
58
planetary differentiation
impacts - increased heat - Fe melting - melt migration to core - more heat (friction)
59
types of meteorites
chondrites achondrites stony-iron iron
60
chondrites
'stony meteorite' - 86% of meteorites - 75-90% Si minerals - bubbly texture (no melting)
61
importance of chondrites
no melting = representation of primative material (before differentiation)
62
achondrites
'stony meteorite' - no chondrules - originate from outer Si mantle
63
Stony-iron meteorite
ca. even Si and Ni/Fe alloy
64
Pallasite
specific type of stony-iron meteorite representing mantle/core boundary
65
Iron meteorite
from large asteroid core, almost fully Ni-Fe
66
Age of Earth
4.56 bya
67
timing of accretion and differentiation
ca. 30 million year
68
radioactive decay
spontaneous disintegration of a nucleus w/ emission of particles and/or radiation
69
half-life
time for half of initial pop. of atoms to decay
70
common radioactive elements
U238 (t1/2 = 4.5by) U235 (t1/2 = 0.7 by) K40 (t1/2 = 1.3 by) Th232 (t1/2 = 14 by)
71
heat transfer due to bulk movement of molecules w/i fluid
convection
72
Lord Kelvin
William Thompson, 1862, estimated age of E to be 100Ma assuming cooling from conduction
73
John Perry
Kelvins assistant, 1895, realized heat transfer was via convection, estimated E age to 2-3 Ga
74
the missing years in the age of E calculations
radioactivity, 1956, Marie Curie, 4.55 Ga
75
convection occurs where in earth
liquid outer core | solid (ductile) mantle
76
drives plate tectonics
convection
77
Internal heat energy responsible for
earthquakes tsunami volcanoes mountains
78
gravity ∝
∝ (M1M2)/distance^2
79
kinetic energy of slides comes from
gravitational potential energy (stored energy)
80
conduction
heat transfer due to particle collision
81
solar energy reaction
H + H --> He + nuclear E (heat + light)
82
driving mechanism of weather and currents
uneven heating of earths fluids
83
why is the E still hot 4.6bya
convection brings heat back into core (+radioactive decay continues)
84
density of earth
average: 5.5g/cm^3 crust: 2-3 g/cm^3
85
how do we know E's density
study gravity -> calculate volume and mass
86
Earths wobble
doesn't really wobble and gravity is constant therefore uniform density distribution in concentric shells
87
solar heating drives
hydrologic cycle currents weather climate
88
how do we know Earths structure
- density distribution - seismic velocity distribution - magnetic field - direct observation - lab studies
89
seismic velocity distribution
seismic waves are reflected/refracted at boundaries
90
Earth's magnetic field
requires convective flow of metallic fluid
91
importance of magnetic fluid
holds atmosphere and provides protection, 'magnetosheath'
92
observations of Earth's internal structure
- only drill to ca. 12km | - kimberlite pipes bring deep mantle material to surface (ca. 200km)
93
lab studies of Earths structure
- high T/P studies | - diamond-anvil apparatus can compress up to 200GPa equivalent to 3000km depth
94
Earth's structure considered in terms of
- chemical composition (what its made of) | - rheology (deformation under stress)
95
Stress =
Force/Area (N/m^2 or Pa)
96
types of stress
compression tension shear
97
compression leads to
contraction
98
compression
force inwards | perpendicular to surface
99
tension
force outwards perpendicular to surface
100
shear stress
force parallel to surface
101
tension lead to
extension
102
rheology of liquids
flow under stress
103
rheology of solids
elastic - recoverable deformation ductile - permanent deformation brittle - rigid object, fractures plastic - high viscosity, flows
104
viscosity
resistance to flow | honey, brie, molasses
105
rheology depends on
t T P compression
106
shear stress leads to
shearing/ destortion
107
short t, low T and/or low P =
possible brittle rupture
108
long t, high T and/or high P =
possible plastic flow
109
example of material with different rheology based on t/T/P
wood bends to an extent if move slow, breaks if move fast glaciers - flow and calve
110
crust
- 0.5% of Earth mass - 0-1000ºC - density 2-3 g/cm^3
111
mantle-crust boundary
Mohorovicic discontinuity
112
Mantle
``` plastic, solid, convecting -67% of mass -1000-3000ºC density 3-6 g/cm^3 -Si rock rich in Fe and Al ```
113
outer core
``` liquid, convecting 30% of mass 4000ºC 10-14 g/cm Fluid Fe/Ni ```
114
Inner core
``` solid 2% of mass 5000º 14-16g/cm^3 Fe-Ni alloy ```
115
basalt
``` oceanic crust volcanic rock 48% SiO2 3 g/cm3 ca. 10km thick ```
116
granitic rock
continental crust 60% SiO2 2.7 g/cm3 ca 35km thick
117
earths structure, compositional
``` continental/oceanic crust upper mantle lower mantle outer core inner core ```
118
earths structure, rheologically
lithosphere asthenosphere mesosphere
119
lithosphere
crust + upper mantle = rocky, rigid
120
asthenosphere
weak, partial melt, flows under stress
121
T, Earths structure
increases nonlinearly w/ depth
122
P, earths structure
increases ca. linearly w/ depth (due to overburden weight)
123
solid inner core vs fluid outer core due to
pressure
124
fluid outer core vs solid mesosphere due to
composition
125
lithosphere floats on asthenosphere at an elevation dependent on
thickness and density
126
floating equilibrium
isostasy
127
change in mass of floating object =
isostatic adjustment - change in elevation fluid
128
density of water
1 g/cm3
129
thickness of oceanic crust
10km
130
depth of continental crust
ca. 35km | up to 80km
131
oceanic crust sits lower in ocean than continental b/c
isostasy | heavier, thinner
132
glacial melting =
isostatic rebound/ postglacial rebound
133
glacial formation =
push crust down -> push water out of way -> uplift of adjacent crust
134
Canada postglacial rebound
Canada raising from melting of Laurentide glacier, US moving back down
135
Mexico city eq
M7.1 51km depth mechanism: normal faulting many deaths avoided due to EWS
136
comparing the Mexico eq's
Sep 8: M8.1, deeper, smaller population, lower vulnerability, 98 deaths Sep 19: M7.1, shallow, higher population, high vulnerability, >250 deaths
137
exacerbation of mexico eq
city expansion onto drained lake bed
138
problems with building on drained lake beds
saturated sediments -> greater shaking for longer period after eq passes
139
example of eq in drained lake bed city
Kathmandu, Nepal in basin- greater shaking for longer near basin - less for shorter
140
liquefaction
saturated soil loses strength and stiffness in response to applied stress causing it to liquify
141
plate deformation
plates are internally rigid, stress at one margin is transferred to the opposite margin, no internal deformation
142
MOR
divergent boundary, rising mantle forms magma, cooling and solidifying forms new basaltic crus pushing plates apart, warm, low-density, topographic high
143
MOR volcanism
decompression melting: geothermal crosses solidus resulting in partial melting
144
transform boundary, transform fault
region where 2 oceanic plates are moving in opposite direction
145
region where 1+ continental plates are moving in opposite directions
trans current boundary, strike-slip fault
146
strike-slip fault example
Pacific plate ^\NA plate (San Andreas Fault)
147
subduction zone
convergent boundary, old, cold, dense oceanic lithosphere, pulled into mantle, melting deep within mantle
148
where 3 plates meet at single point
triple junction
149
when oceanic crust is fully subjected and continental crust converges
continental collision zone
150
results of continental collision
mt building, continental crust too buoyant to subduct | ex. Himalayas, Rockies
151
Himalaya characteristics
8km above sea-level 5km average elevation 80km crustal thickness
152
normal-thickness of continental crust
35km
153
continental collision zone
- wider than oceanic plate boundaries - form mountains - convergent w/ large strike-slip faults moving blocks out of way
154
divergent plate boundary that forms new ocean basin
continental rift
155
thinned edges of continent following continental rift
passive continental margin - not plate boundaries, separate continent and oceanic crust of same plate
156
example of continental rift
east african rift - eastern Africa (Somalian plate) will split off of rest of Africa (Nubian plate)
157
upwelling mantle plume
hot spot
158
hot spots occur
anywhere (not associated w/ plate boundary)
159
hot spot examples
Hawaii Yellowstone Iceland Azores
160
hot spot mechanics
thermal anomaly -- mantle hotter than normal -- geothermal crosses solidus (at depth) -- plume rises
161
submerged volcano
seamount
162
Hawaiian hotspot
Pacific plate has moved NW over hotspot for at least 5Ma = chain of islands and seamounts
163
evidence of Hawaiian hotspot
- 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
Hawaiian Island/Emperor Seamount chain
- 6000km long | - kink at 43Ma (plate changed direction)
165
yellowstone hot-spot track
NA plate moving W over hotspot
166
Alfred Wegener
1912, proposed single supercontinent (Pangaea) and continental drift
167
Pangaea ocean
Panthalassa
168
Pangaea period
Jurassic
169
Evidence for plate tectonics
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
Glacial striation plate tectonics
- continents that could not be glaciated (Australia, India, SA) - wrong direction of movement (onto land from ocean)
171
Pangaea breaks into 2 supercontinents
180 Ma, Jurassic
172
supercontinents after Pangaea
Laurasia, Gondwanaland
173
Future supercontinent
+250Ma, NA/SA collide with Africa/Eurasia
174
How plate tectonics were discovered
WWII and cold war provided geophysical data, 1960s, Harry Hess
175
John Tuzo Wilson
1963-1966, Canadian, described Hawaiian chain, transform faults connecting MORs
176
surface elevations measured
satellite imagery
177
NAtl begins opening
135Ma, early Cretaceous
178
S. Atl opens, Africa reaches Europe
65Ma, end Cretaceous
179
surface elevation distribution
bimodal; continental crust centred around 0km elevation, oceanic around -5km, average ca. -3km
180
study of earths magnetic field through time
paleomagnetism
181
when geographic north pole = magnetic south pole
reverse polarity | geomagnetic reversal
182
paleomagnetism evidence
magnetite (Fe3O4) in basalt aligns w/ current magnetic field
183
process of magnetic minerals aligning w/ magnetic field
thermal-remant magnetization (TRM)
184
magnetic polarity scale
black shows normal polarity, white = reverse
185
sea-floor striping
symmetric pattern of magnetic anomalies radiating out from MOR
186
discovered, explained sea-floor striping
Fred Vine, Drummond Mathews, 1963
187
age of oceanic lithosphere
all less than 300 million years old
188
age of continental rocks
up to billions of yrs
189
first earthquake detection
1960s, World Wide Standardized Seismograph Network (WWSSN) (to monitor nuclear explosions)
190
narrow earthquake belt
MORs
191
subduction zone earthquakes
Wadati-Benioff zones, unusually deep, down to 700km
192
Plate tectonic forces
1. Ridge push | 2. Slab pull
193
wide earthquake belt
subduction zones
194
ridge push
upwelling mantle and gravitational collapse of young (warm, buoyant) oceanic crust at MOR
195
slab-pull
due to old, cold, dense oceanic lithos. in subduction zone
196
widest eq belts
continental collision
197
80% of erupted magma
from spreading centers
198
types of volcanoes
shield volcano | stratovolcano
199
stratovolcano
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
Hot spot volcanism
- 10% of magma erupted - runny lava - not explosive, less hazardous
201
continental volcanism
- explosive | eg. Yellowstone caldera-forming eruption
202
Iceland
BOTH MOR and hotspot - erupts huge volumes of magma - decompression melting and eruption
203
fault
planar surface of plate
204
earthquakes occur
along faults (possibly multiple), not at a point
205
slip
displacement of surface along fault from surface rupture
206
fault planes
planar, striations, corrugations, indicate direction of slip
207
point on fault plane where slip starts
hypocenter
208
types of faulting
- reverse - normal - strike-slip
209
reverse faulting
'thrust faulting' - horizontal convergence - force in, block thrust up - gentle dip angle ca. 30º
210
strike-slip fault
plates move laterally past each other
211
right-lateral strike slip
opposite block moves to the right
212
graphical representation of type of faulting involved in eq
focal mechanism
213
earthquake cycle
stress builds on fault -- released quickly
214
point directly above hypocenter
epicenter
215
steady motion occurs pulling block away from fault but fault is 'locked'
interseismic period
216
normal faulting
horizontal extension - pull apart, one block slides down - dip angle steeper, ca. 60º
217
fault rebounds causing eq
coseismic phase, now offset at fault
218
megathrust faults
subduction zone, vertical and horizontal motion, stick-slip
219
megathrust fault cycle
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
elastic rebound releases
stored as energy as seismic waves
221
2 classes of seismic waves
body waves | surface waves
222
Body waves
- move through Earth - P waves - S waves
223
Surface waves
- do not move through the body of Earth - Raleigh waves - Love waves
224
P waves
compressional waves - primary, first to arrive - compress, push stationary object - no z direction movement, forward/back like a worm
225
S waves
Shear waves - secondary - S-shape movement in z direction (up, down waves) - sheers stationary object, squishes square up into a diamond
226
instrument that measures and amplifies ground motion
seismometer
227
how seismometer works
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
distinguishing waves on a seismogram
- by time of arrival | - by component of seismogram
229
Raleigh wave
- 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
records ground motion from seismometer
seismograph
231
seismogram components
Horizontal (radial, transverse) Vertical -3 components
232
Love wave
- side to side waves on surface, y direction, like a snake | - move particle side to side
233
seismogram
graphical representation of motion at a given point as a fn of t
234
distinguish waves on seismogram from t
1st: P-waves 2nd: S-waves 3rd: Love 4th: Rayleigh
235
distinguish waves on seismogram from component
Vertical: P-waves, Rayleigh Horizontal transverse: Love Horizontal radial: S-waves, Rayleigh
236
largest amplitude waves
surface (most damaging)
237
slower waves
- surface (arrive later) slower than body | - s slower than p
238
seismic waves that travel through liquid (outer core)
P-waves
239
how we determine interior structure of E
refraction, reflection of body waves by major boundaries in E (shadow zones)
240
further seismic stations
record P and S as farther apart b/c P travelling faster
241
distance btw earthquake and seismometer
``` Ts = x/Vs; Tp=x/Vp x = VpVs(Ts-Tp)/(Vp - Vs) ```
242
pinpointing eq epicenter
determine distance from eq to seismometer for 3 locations, plot them, where they cross
243
Eq Early Warning system
- 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
determining magnitude
- observed seismic waves - correct for distance - cross plot distance, magnitude, amplitude
245
moment (Nm)
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
exploring magnitude equation
- fault area and displacement highly correlated - rupture area KEY to magnitude - large eq's rupture large faults (subduction zone)
247
subduction zone eq's
megathrust - gently-dipping interface of thrust fault + long = large SA - can generate large tsunami - 17/20 largest eq's since 1900 were megathrust
248
major west coast fault zones
San Andreas Fault (SAF) | Cascadia Subduction Zone (CAS)
249
which major west coast fault zone is likely to produce a larger eq
CAS - subduction zone, larger SA
250
an increase in M of 1 unit =
- 30X increase in E | - 10X reduction in frequency
251
M =3, E equivalent to
- World's largest nuclear test | - Mt. St Helen eruption
252
M = 6, E equivalent
Hiroshima atomic bomb
253
global cumulative seismic moment release
- dominated by megathrusts | - 5 >9.0 megathrusts = more than 1/2 of moment released from 1900-2014
254
entire length of Pacific ring of fire subduction zone
30,000 km
255
max slip ever observed
50m
256
max magnitude eq
10.5 if every subduction zone in the world erupted at once
257
max realistic earthquake
entire Aleutian trench (between Asia and NA) or Peru-Chile trench = M9.9
258
describing earthquakes by felt intensity
Mercalli Scale -instrumental, weak, slight, moderate, rather strong, strong, very strong, destructive, violent, intense, extreme, cataclysmic (12)
259
Isoseismal map
concentric contours of equal seismic intensity focused on approximate epicentre
260
isoseismal map bias
- proximity of eq to population centre | - personal account exaggeration
261
what governs felt intensity
- magnitude - distance from eq - depth of eq - infrastructure height, quality - earth surface
262
Similar magnitude different intensity
M5.8 Mineral, VA M6.5 San Simeon, Ca felt much further away in VA due to bedrock geology, easily felt 1000km away
263
why eq felt further away in Eastern US
less tectonics = less broken up plates = less dissipation/attenuation of seismic energy
264
Intensity of eq's with same magnitude, different depth
M6.5 San Simeon, CA, 7km M6.3 New Zealand 163 km NZ = barely any reports of people feeling it
265
MOR earthquakes
- normal faulting - young, warm, thin ocean crust - eq's generally small
266
Transform fault eq
- strike-slip faulting - older, colder, thicker crust than MOR - larger magnitude than MOR
267
part of uppermost crust brittle enough to host earthquakes
seismogenic layer
268
transform fault
adjacent plates are moving in opposite direction
269
fracture zone
adjacent plates are moving in same direction = no faulting = no earthquake
270
Earthquakes that occur at subduction zones
crustal eq (small), megathrust (large), intermediate eq, deep eq, outer rise normal fault eq
271
outer rise normal faulting eq
few, large, where incoming oceanic plate begins to flex | -not very hazardous due to proximity (at MOR)
272
deep earthquakes
- up to 700im - only in subduction zones w/ rapidly descending plate - usually too far to be dangerous
273
why do deep eq's only occur if plate is descending rapidly
so it stays cold and brittle, if it subduct slowly it will warm up and lose brittle nature needed to conduct eq
274
Intermediate earthquakes
50-300 km - in all subduction zones - can be very dangerous - intraslab, within subducting slab
275
what type of earthquakes were the Mexico quakes?
subduction zone, intermediate | -top of subducting Cocos plate
276
classes of hazardous earthquakes in Cascadia
1. Intermediate/ intraslab 2. megathrust 3. crustal
277
Intermediate eq example
Nisqually WA, 2001, hypocenter 57km depth, 1 death, 1-4billion in damages
278
Cascadia's last megathrust
1700AD
279
Cascadia megathrust max size, recurrence
M9, 500-600yr
280
deep JDF plate max eq and recurrence
M7+, 30-50yr
281
West coast crustal quake max size and recurrence
M7+, hundreds of years?
282
Crustal earthquakes
-moderate magnitude -could be close to pop centre -
283
VI crustal fault
Leech River fault | -right across southern tip of island
284
airborne laser mapping that penetrates forest canopy to determine surface topography
lidar
285
continental plate boundary earthquakes
shallow, potentially close to populations - broken up crust, no megathrust - seismogenic layer ca. 15km - M7-8 - mostly along collision zone
286
continental plate boundary example
Bam, between two deserts - half of pop lost due to poor infrastructure (adobe) - eq rupture along escarpment Bam-Baravat ridge
287
Why Bam is an oasis
- ridge = impermeable, dam on water table | - build tunnels to tap water source, irrigate crops
288
the bittersweet side of Iran faults
- water sources | - active faults!
289
Tehran
continental plate boundary - pop. 14 million - destroyed by 4 past eps - city centre right next to Alborz mountains
290
continental plate deaths
more than subduction zones even though smaller magnitude
291
intraplate earthquakes
- unusual, infrequent - hazardous - b/c plates are not perfectly rigid - variety of faulting mechanisms
292
Intraplate seismicity in eastern Canada associated with
-passive continental margins or -ancient failed rifts
293
passive continental margin
- edge of continent | - btw continent, ocean on SAME plate
294
failed rifts, Canada
from formation of Atlantic (branches that failed) | eg. Labrador Sea
295
intraplate earthquake stresses
1. Plate tectonic stress 2. postglacial rebound 3. Manmade stresses
296
Plate tectonic stresses on intraplate
ridge/push, slab/pull stresses generated through interior of plate
297
Postglacial rebound, intraplate earthquake example
-Parvie fault scarp, Sweden M8, 10ka -1989 M6 Ungava, Quebec
298
Induced intraplate eq example
Oklahoma, Colorado, Texas, Alberta, N BC
299
building to resist earthquakes
1. Make building resistant to horizontal movement 2. Make resistant to stress 3. reduce resonance 4. base isolation
300
how to make buildings resistant to horizontal shearing
braces, brackets, shear walls, bolts
301
how to make buildings resistant to stress
Wood - flexible, light, elastic | Steel - strong, ductile
302
reducing resonance
depends on size, substrate (bedrock/sediment), weight distribution, shape, building material, foundation
303
Resonance rule of thumb
buildings sway at resonant frequency 10 Hz / # of stories
304
base isolation
- 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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