Earthquakes

Question 1

Earthquake

Answer 1

shaking (vibration)produced by the rapid release of energy

Question 2

Generates seismic waves

About earthquakes

Answer 2

that travel through the Earth

Question 3

Focus

Answer 3

point of energy release; radiates out in all directions (hypocentre) - when rupture of fault plan started

Question 4

Epicentre

Answer 4

point on Earth’s surface directly above focus

Question 5

Where do earthquakes occur?

Answer 5

Along faults with plate boundaries

Question 6

Three levels of fault depth

Answer 6

Shallow, intermediate, deep

Question 7

Shallow (which boundaries?)

Answer 7

divergent and transform boundaries

Question 7

Shallow to deep

Answer 7

Convergent boundaries

Question 8

Which depth causes most damage

Answer 8

Shallow

Question 9

Increasing distance from focus results in

Answer 9

Diminished shaking strength

Question 10

Intraplate earthquakes

Where and what depth?

Answer 10

Far from boundary, shallow

Question 11

Earthquake Early Warning

Answer 11

Rapid detection, real-time estimation of shaking hazard

Question 12

Last major quake, what depth

Answer 12

April 2015, Nepal

Shallow

Question 13

Nepal earthquake triggered

Answer 13

Landslides and avalanches

Question 14

interplate vs intraplate earthquakes

Answer 14

Occur at plate boundaries vs. occurrence in the interior of the plate boundaries

Question 15

Earthquake magnitude

Measurement of what radiated by an earthquake?

Answer 15

Objective measurement of the energy radiated by an earthquake

Question 16

Richter magnitude vs moment magnitude

Answer 16

Based on distance and amplitude vs. measurement of amount of energy released by earthquake

Question 17

Moment magnitude (in depth)

Factors in measurement

Answer 17

size of area where movement occurs, distance moved, rock type, combines data from seismograms and seismic moment

Question 18

Modified Mercalli Intensity Scale

Answer 18

Qualitative way to describe/compare earthquakes, 12 levels

Describes effects on a place, natural feature, buildings, or humans

Question 19

Magnitude

q vs. q

Answer 19

Quantitative measure of amount of energy released at its source earthquake, one magnitude, not variable

Question 20

Intensity

Magnitude vs. Intensity (q vs. q)

Answer 20

Qualitative, amount of shaking, variable - depends on location

Question 21

Fault

Is a response to? That allows what?

Answer 21

Response to stresses in the rock

Allows blocks to move relative to each other

Question 22

Plate boundaries are

made up of

Answer 22

made up of a series of faults

Question 23

Stress

What does this force do to the rock?

Answer 23

Force acting on rock, changes shape and/or volume

Question 24

Rupture | starts at

Answer 24

starts at focus and propagates outwards; seismic source

Question 25

3 types of faults

Answer 25

Normal, reverse, strike-slip

Question 26

Reverse and thrust faulting | Which boundaries?

Answer 26

Convergent: Raise up relative to rocks across the fault, compression

Question 27

Normal faulting

Answer 27

Drop down relative to rocks across the fault, extension

Question 28

Strike-slip faulting

Answer 28

Slide laterally relative to rocks across the fault, right-lateral fault plane

Question 29

What plate boundary is associated with each fault?

Answer 29

Normal - divergent plate boundaries Reverse - convergent Strike-slip - transform

Question 30

Rayleigh waves - surface waves

Answer 30

Arrive after body waves, most damaging, rolling motion

Question 31

P-waves

Answer 31

Compressional waves, arrive first, travel through solid, liquid, and gas, compression and stretching

Question 32

S-waves

Answer 32

Shear waves, second to arrive, travel only through a solid, up and down

Question 33

Longest fault zone

Answer 33

San Andreas Fault System, 1200km long

Question 34

What frequencies do seismic waves have? Which buildings do they affect?

Answer 34

Low frequency - tall buildings vibrate High frequency - low buildings vibrate

Question 35

Attenuation | About high-frequency waves How does this occur?

Answer 35

Weakening or removal of high-frequency waves Occurs with increased distance, low frequency waves travel farther

Question 36

Mexico City quake - why so much damage? | What frequency waves?

Answer 36

Low frequency waves, building heights 6 to 15 stories

Question 37

Material amplification

Answer 37

Subsurface materials respond differently to seismic waves Shaking increases in unconsolidated sediment (mud high shaking, igneous rock low shaking)

Question 38

Seismic Gap | L P Gap

Answer 38

e.g. Loma Prieta gap post-earthquake aftershocks fill the gap, meaning smaller earthquakes in the same general area days to years following a larger event

Question 39

Subduction zone earthquakes

Answer 39

Also known as megathrust earthquakes, convergent plate boundaries, largest earthquakes on Earth

Question 40

What type of faulting is involved in a subduction zone earthquake?

Answer 40

Reverse fault, thrust fault - shallower dip, meaning its stronger

Question 41

Land elevation changes

Answer 41

Uplift and shortening on overriding plate prior to the rupture, extension and subsidence afterwards

Question 42

Where is the Cascadia Subduction Zone

Answer 42

3 plates: Explorer, Juan de Fuca, Gorda Considered "locked in zone" West coast of America and Vancouver Island

Question 43

What 2 plates are involved in the CSZ

Answer 43

Oceanic plate and continental plate

Question 44

Evidence for past megathrust earthquakes in CSZ

Answer 44

Oral traditions of First Nations and physical evidence (e.g. coastal ghost forest in Pacific NW)

Question 45

When is the next 'big one'?

Answer 45

Canada's West Coast, also causing a tsunami

Question 46

What is a locked fault

Answer 46

A fault that does not slip due to high friction, causes uplift in overriding plate and stored strain, resulting in a high magnitude earthquake once strain is overcome

Question 47

Earthquake hazard?

Answer 47

Any physical phenomenon that may produce adverse effects on human activities

Question 48

Primary hazards

Answer 48

caused directly by fault movement=ground shaking

Question 49

Secondary hazards

Answer 49

caused as a consequence of ground shaking

Question 50

Primary hazard examples

Answer 50

Ground shaking (christchurch) and surface rupture (Kaikoura)

Question 51

Secondary hazard examples

Answer 51

Liquefaction , landslides, fires, tsunami, land elevation changes, disease and poverty