tectonics kq3 - features of EQs

Question 1

how are earthquakes formed

Answer 1

1. tectonic plates move = exert a lot of friction on each other = parts of the crust to get stuck
2. plates continue to move = rocks at the stuck crust starts to bend = store large amount of energy = huge amount of pressure builds up gradually at the stuck crust
3. Rocks eventually can no longer contain the pressure = stuck crust slips into a new position = may crack to form new faults in the process.
4. Stored energy is released through faults as seismic waves = causes vibration in the Earth’s crust = earthquakes
   1.

Question 2

how can depth of focus/distance from epicentre affect magnitude of eq

Answer 2

1. Deeper/shallower focus OR further from/closer to epicentre

Seismic waves travel a longer/shorter distance
underground before reaching a place on
the surface
⇩
More/less energy dissipated along the way = Energy would be less/more concentrated when it arrives at the place on the surface
⇩
Seismic waves would have less/more energy by then = less/more shaking
⇩
Lower/higher magnitude

Question 3

how can time of occurrence affect intensity of eq

Answer 3

Earthquake that occurs in the day/night

Most people would be awake/asleep
when the earthquake happens
⇩
People will be better/less abled to react to the earthquake as it happens e.g. move themselves to safety, turn off gas taps/stoves before evacuating
⇩
Less/more injuries and deaths
Less/more damage to infrastructure (due to fires)

Question 4

how can population density affect intensity of eq

Answer 4

Lower (eg farms)/Higher (eg cities) population density
- Shorter/taller buildings = hold less/more more people in an area
- People and buildings are placed
further apart/closer togrther
- Less/more infrastructure built
⇩
When earthquake strike,
- Lesser/more people and properties experience the earthquake
- Easier/harder for people to evacuate from shorter buildings and keep themselves out of collapsing buildings
⇩
- Less/more injuries and deaths
- Less/more properties being damaged

Question 5

how can type of soil decrease magnitude/damage of eq

Answer 5

Cities built on rocks
Harder for parts of solid rocks to move as compared to loose soil
⇩
Harder for seismic waves to vibrate,
= less shaking = the ground will be more stable (magnitude)
⇩
Less damage to infrastructure (damage)

Question 6

how is destruction of properties and infrastrucuture a risk of eq

Answer 6

DESC: many buildings, properties and infrastructure, such as bridges, may lose its support and collapse → more common in LDCs where their buildings are made out of flimsier cheaper materials
Fires can also break out, burning down infrastructure (may have withstood the shaking but still get burned down)
⇩
Destruction of properties
EXP:
1. buildings and Infrastructure collapse = debris can crush and trap the people in it.
2. Many are left homeless as a result, which exposes them to more dangers from aftershocks.
Would have to live in temporary shelters = poor sanitation, cramped = outbreak of diseases = lower SOL/moredeaths

⇩
wide-spread
injuries and
deaths.

Question 7

how is lanslides a risk of eq

Answer 7

DESC: Ground shakes, loosens soils = weaken slopes of hills and mountains
⇩
Soil slides down mountains at high speed
⇩
Landslide
EXP:
the landslide would bury anyone further downhill with large quantity of soil = more deaths
- The landslide would also destroy roads/bury and block roads = prevent rescuers from reaching the affected areas in time to save lives = more deaths

Question 8

how is disruption of services of eq

Answer 8

DESC: underground pipes and cables throughout the city may snap and break
⇩
loss of essential services in the city, such as telephone
lines, water, sewage, gas,
and electricity.
EXP:
1. the loss of essential Services = harder for rescue operations to be carried out = harder for survivors of the earthquake to survive = more may die
2. Rupturing of gas pipes and electricity cables = trigger fires throughout the city = more injuries, deaths, damage

Question 9

how is tsunamis a risk of eq

Answer 9

DESC: Unusually large sea waves formed due to
- Underwater earthquakes
- Huge landslides

Widespread deaths and destruction
Tsunami waves can rush inland for a few kilometre due to the huge amount of energy it has. In the process, it will
- Drown those in its path
- Push huge debris (such as ships and cars) at a fast speed, killing those in its path.
- Destroy buildings and causing them to collapse and kill those in it.
⇩
the wave will pull most things in its path
far back into the sea = drowning survivors caught in the tsunami
⇩
Tsunami had several waves = process repeated

Question 10

how can type of soil increase magnitude/damage of eq

Answer 10

Cities built on loose soil
Easier for parts of loose soil to move as compared to solid rocks.
⇩
Easier for seismic waves to vibrate = amplify seismic waves = more shaking like water waves (liquefaction) = ground less stable (magnitude)
⇩
More damage to infrastructure (damage)