Seismic hazards revision :)

Question 1

Name 3 facts about PRIMARY waves

Answer 1

Fastest
least destructive
go through the centre of the Earth
longitudinal waves

Question 2

Name 3 facts about SHEAR/SECONDARY waves

Answer 2

1/2 as fast as primary waves
only travel through SOLIDS (not Earth’s core)
Transverse waves

Question 3

What are Ray-leigh waves?
What are Love waves?

Answer 3

Ray-leigh and Love =
- most destructive waves
- Slowest waves

Question 4

What is an earthquake?

Answer 4

Shaking of Earth’s surface.
Result of sudden energy release in the lithosphere.
This creates seismic waves.

Question 5

Where can you find earthquakes?

Answer 5

Found at ALL plate boundaries.

Divergent plate boundaries:
North American and Eurasian plates separating.

Convergent plate boundaries
(Nazca and South American plate)
Continental + continental = India and Asia colliding along Himalayas.

East African Rift Valley
Mid Atlantic ridge.

Transform plate boundaries
San Andreas fault - pacific plate moving faster than north american plate.

Question 6

What is the plate boundary at Haiti?

Answer 6

North American plate and caribbean plates are moving side by side.

TRANSFORM.

Question 7

Define a fault line

Answer 7

A weakness within the lithosphere.

Question 8

What is a focus?

Answer 8

THe point within the crust where the energy of the earthquake is released.

Transferred across the crust in seismic waves.

Question 9

What is the name of the point directly above the focus?

Answer 9

The epicentre.
Where the intensity of the Earthquake is likely to be strongest because it is the nearest point to the surface. The seismic waves have lost the least energy at this point.

Question 10

What are the differences between earthquake storms and earthquake swarms?

Answer 10

Storm:
Earthquake activity moves along a fault line over years. One earthquake has built up stresses on the fault.

Swarm:
lots of earthquake activity of same magnitude happening around the same time. Usually a result of volcanic activity - impending eruptions.

Question 11

How is a Earthquake storm different from an aftershock?

Answer 11

storm is earthquakes do not trigger another one, just transfer stress. Storm earthquakes also happen multiple years apart.

Question 12

What is an example of an earthquake storm?

Answer 12

1999 Turkish Earthquake on North Anatolian Fault.

Question 13

WHat is an example of an earthquake swarm?

Answer 13

Indonesia:
Island of Lombok hit by 29 earthquakes over 4 on the Richter scale.

Question 14

What is the Moment Magnitude Scale?

Answer 14

Measures energy released during an earthquake

Logarithmic

uses seismometers to record ground motion and calculate magnitude

open ended.

Question 15

Modified Mercalli INTENSITY:

Answer 15

Measures effects
based on observed effects
Scale from I to XII
Values vary with distance from epicentre
Only useful in inhabited areas.

Question 16

MMS (moment magnitude scale) and MMI (modified mercalli intensity) can vary. Give an example of this in the 2011 Japanese quake.

Answer 16

2011 Japan Tohoku quake:
MMS = 9
MMI = IX

Question 17

Give an advantage and disadvantage of the Richter scale

Answer 17

Advantage: Based off accurate recordings
scientists can compare strength at different times

Disadvantage:
seismograph have limitations - can underestimate energy released, calculated with one type of seismic wave.

Question 18

give 3 primary hazards of seismic activity

Answer 18

Ground shaking
ground rupture
buildings collapse

Question 19

Give some secondary hazards of seismic activity:

Answer 19

Fires
Shockwaves
avalanches (Nepal 2015)
Landslides (2021 Haiti, 14th August)
Tsunami (2004, December Boxing Day Tsunami)
Liquefaction (palu - indonesian- earthquake of 2018.

Question 20

Environmental impacts
short term?
Long term?

Answer 20

ST: ruined habitats, flooding, fires, landslides,

LT: Changed landscapes

Question 21

Social impacts?
Short term?
Long term?

Answer 21

ST: Disease, injury, death, looting, increased tax (2011 Japan = 10% tax raise to pay for rebuild)
disrupted transport, food, water, sanitation decrease.

LT: Rebuilding, disease and death, tax, homelessness, education disruption

Question 22

Political impacts
Short term:
Long term:

Answer 22

ST: Loose faith in gov.
LT: Better mitigation programmes developed

Question 23

Economic impacts of quakes:
Short term?
Long term?

Answer 23

ST: income lost, unemployment,

LT: income lost, unemployment, shops/businesses destroyed, £ needed to rebuild.

Question 24

How do we respond to seismic hazards?
PREPARATION:

Answer 24

Emergency plans
supply kit
education of public
safe spaces e.g bunkers
group hubs (to ensure everyone’s accounted for in a hazard event)

Question 25

How do we respond to seismic hazards?
MITIGATION:

Answer 25

Prediction
Authorities can allert public through technology (Haicheng, China - 90,000 people saved from 7.3 quake)
Emergency services are up to scratch.

Question 26

How do we respond to seismic hazards?
PREVENTION:

Answer 26

Disaster plan
create specialised infrastructure - Japan = shock absorbers (buildings built on rubber blocks)
strengthen existing infrastructure - wire mesh
checks for damage after event to prevent after effects,

Question 27

How do we respond to seismic hazards?
ADAPTION:

Answer 27

Heavy breakable objects on lower shelves
Specialised infrastructure.
Land use planning

Question 28

How do we predict seismic hazards?

Answer 28

Detect changes in:
Radon + Thoron levels
ground surveying (movement)
upwelling of water
seismometer - monitor prequakes
tiltometer/magnetometer
sonar dishes - detect changes along fault line.

Question 29

What are the limitations of predicting earthquakes?

Answer 29

NOT reliable
Evacuations can be very disruptive
some warning signs only recognisable in hindsight.
distrust in gov / scientists if quake doesn’t happen.

2009 L’Aquila earthquake, Italy, 6 scientists + 1 government official jailed for giving ‘overly-reassuring’ advice.

Question 30

In an LEDC, it is more difficult to adapt, prevent, predict, prepare and mitigate. Why?

Answer 30

Lack of money, lack of tech, large populations (leading to urban sprawl so land use zoning is hard)

Question 31

How are Tsunamis detected?

Answer 31

Seabed monitors - detect changes in pressure.

Question 32

What are the three ps of hazard management?

Answer 32

Prediction
protection
preparedness.

Question 33

Protection of earthquakes:

Answer 33

Computer controlled weights on roof to reduce movement, foundations in bedrock, rubber shock absorbers, fire resistant building materials, automatic shutters (stop broken glass travelling), ‘bird cage’ interlocking steel frame.

CORRUPTION can cause building codes to be bypassed!
Need to ‘retrofit’ original infrastructures.

Question 34

Preparedness in earthquakes

Answer 34

The great shakeout (earthquake drill in America)
Phrases - Drop! Cover! Hold on! (USA)
‘Go-Bags’ - bags containing essential supplies in evacuation times.

Drills - boring, create false sense of security
LEDCS - limited access to tech and low literacy = barrier.

Question 35

How did tech help the response in the 2010 Haiti earthquake?

Answer 35

Openstreetmap - enabled a good map to be created through satellite imaging.

In Nepal 2015 - shelter areas popped up on openstreetmap.

Question 36

Why are phones effective in earthquakes?

Answer 36

GPs tracking and mapping areas
show where damage and blockage is - good for rapid response units.

Question 37

What factors can impact the effectiveness of a response?

Answer 37

economic development
resource base
antecedent conditions / extenuating circumstances like previous natural hazards.
governance of an area

Question 38

How do tsunamis form?

Answer 38

over-riding plate of a convergent plate boundary springs up - water above is displaced.

Question 39

what might influence the effects of a Tsunami?

Answer 39

Population density
coastal relief / morphology
land use

Question 40

How might we mitigate against a Tsunami?

Answer 40

Pacific Tsunami Warning system
Gives hours of notice
uses sea bed monitors to detect changes in pressure.

Question 41

True or false - Tsunamis are a singular wave?

Answer 41

FALSE.
Multiple waves. The first one may not necessarily be the biggest wave.
40% of wave energy is transferred back out to sea so waves keep gaining energy.