earthquakes

Question 1

layers of the earth

Answer 1

lithosphere (crust): brittle, locally ductile
asthenosphere (mantle): very ductile
mesosphere (lower mantle): stiff ductile

Question 2

what are plate tectonics controlled by?

Answer 2

temperature
density
compression
gravity

Question 3

which crust is more dense, oceanic or continental?

Answer 3

oceanic

Question 4

types of deformation

Answer 4

elastic (springs back)
ductile (plastic flow)
brittle (breaks)

Question 5

what are phase changes controlled by?

Answer 5

temperature & pressure

Question 6

only ___ plates subduct

Answer 6

oceanic
continental plates are too buoyant

Question 7

forces acting on the plates

Answer 7

basal drag: friction between rigid lithosphere & more ductile mantle drags plate along
slab pull: cold descending plate pulled beneath hot mantle by gravity
ridge push: heating at rift raises crest, gravity pulls it down

Question 8

plate boundaries

Answer 8

convergent
divergent
transform

Question 9

convergent boundary

Answer 9

force: compression
earthquake: thrust or reverse
strongest quake
boundaries: O-O, O-C, C-C

Question 10

divergent boundary

Answer 10

force: tension
earthquake: normal
weakest quake
boundaries: O-O, C-C

Question 11

transform boundary

Answer 11

force: shear
earthquake: strike/slip
boundaries: all

Question 12

fault definition

Answer 12

brittle fracture along the rocks in which movement has occured

Question 13

the release of stored elastic energy is…

Answer 13

an earthquake

Question 14

sequence of seismic events

Answer 14

1. elastic deformation
2. brittle failure
3. earthquake
4. elastic rebound

Question 15

body waves

Answer 15

travel inside materials
p waves & s waves

Question 16

p waves

Answer 16

moves in same direction wave propagates, the fastest, compression driven

Question 17

s waves

Answer 17

perpendicular to direction wave propagates, slower, shear force driven

Question 18

surface waves

Answer 18

travel along boundaries between materials
slower than body waves
rayleigh waves & love waves

Question 19

rayleigh wave

Answer 19

parallel to wave travel direction

Question 20

love wave

Answer 20

perpendicular to wave travel direction

Question 21

sequence of waves on a seismograph

Answer 21

p waves -> s waves -> surface waves

Question 22

magnitude definition

Answer 22

indicates how much energy was released

Question 23

magnitude scales

Answer 23

richter - based on maximum ground motion

Question 24

for each increase on magnitude scale, energy released increases by a factor of…

Answer 24

10^1.5 or around 32

Question 25

intensity definition

Answer 25

how strong ground motion is at felt location

Question 26

intensity scales

Answer 26

modified mercalli scale

Question 27

what factors influence our perception of intensity?

Answer 27

• magnitude
• distance from hypocentre
• structural resistance
• duration

Question 28

why can’t shear waves propagate thru fluids?

Answer 28

you can’t bend a liquid, but you can compress it

Question 29

how different types of motion affect buildings

Answer 29

horizontal shaking & rolling motions most destructive
vertical shaking relatively undestructive

Question 30

hazards of earthquakes

Answer 30

• ground shaking -> things falling
• liquefaction
• fire
• tsunami
• landslides

Question 31

best building design to withstand earthquakes

Answer 31

• flexible and strong
• resonates at high frequencies

Question 32

building damage mitigation

Answer 32

• tuned mass dampers
• massive pendulum within a building
• decouple building from its base

Question 33

short term warning signs

Answer 33

• increase in seismic activity
• rapid ground deformation
• electromagnetic disturbances
• animal behaviour

unreliable at best

Question 34

long term prediction method

Answer 34

evidence of past quakes, imprecise prediction

Question 35

a forecast is a…

Answer 35

probability statement

Question 36

earthquake forecasting tools

Answer 36

• land-level change
• seismic gaps
• physical and chemical phenomena

Question 37

cascadia subduction zone return period, which plates

Answer 37

500 years, juan de fuca plate subducting under north american plate

Question 38

evidence of 1700 cascadia earthquake

Answer 38

• indigenous stories
• japanese writings
• ghost forest
• sediment deposits

Question 39

what to do during an earthquake

Answer 39

• anchor objects that might fall
• hide under desk
• avoid doorways and the kitchen
• after help the injured
• evacuate damaged buildings after