Seismic Hazards

Question 1

How do 2 transform plates become ‘stuck’? What is the impact of this?

Answer 1

• Plates do not fit perfectly into each other- meaning they do not move in fluid motions.
• Friction between plates causes them to become stuck.
• Convection currents from the asethenosphere continue to push against the plates, increasing pressure.
• This pressure cannot be sustained, causing the plates to jolt.
• This jolt is responsible for seismic movement via seismic waves.

Question 2

What is the focus?

Answer 2

The point underground where the earthquake originates from.

Question 3

What is the epicentre?

Answer 3

The area above ground that is directly above the focus.

Question 4

What is the spacial distribution for earthquakes?

Answer 4

• Occur along all boundaries
• The ring of fire accounts for 90% of all earthquakes.
• The Alpine-Himalayan belt accounts for 5% of all earthquakes.

Question 5

How is the magnitude of earthquakes measured?

Answer 5

• Richter scale

Question 6

What are the two main hazards that can be caused by earthquakes?

Answer 6

• Shockwaves (seismic waves)
• Tsunamis

Question 7

How do shockwaves occur from an earthquake(seismic waves)?

Answer 7

• When two transform plates move side by side they can become stuck, causing friction to build up and for pressure to increase; this pressure is stored as potential energy.
• This pressure is unsustainable as it builds up, causing the plates to eventually move.
• The pressure stored as potential energy is transferred into kinetic energy, which is released and vibrates through the ground.
• The further away from the focus, the weaker the shockwaves are (as the energy is transferred to the near surroundings).

Question 8

How do tsunamis occur from an earthquake?

Answer 8

• When an oceanic crust is jolted during an earthquake, all the water above the plate is displaced.
• This water will travel fast with a low height.
• As it gets closer to the coast, the sea level decreases, producing friction between the sea bed and waves.
• This friction causes the waves to slow and gain height, creating a ‘wall’ of water.

Question 9

What is liquefaction? How does it occur?

Answer 9

• Process where liquid-saturated sediment loses setrength and acts similarly to a fluid.
• When a soil is saturated, the vibrations of an earthquake cause it to act like a liquid.
• Soil becomes weaker and is more likely to subside with a large weight on it.

Question 10

How can we prevent an earthquake?

Answer 10

• Majority of earthquakes cannot be prevented (except for those caused by fracking).
• Liquefaction of soils can be prevented through soil stabilisation.
• Avalanches can be prevented through controlled explosions.

Question 11

How can we prepare for an earthquake?

Answer 11

• Earthquake prone areas (such as Japan) have extensive awarness stategies and education in place e.g. drop, cover.
• Earthquake and tsunami warning systems are in place.
• Evacuation routes prepared.
• Training rescue teams

Question 12

How can we mitigate the effects of an earthquake?

Answer 12

• Search and rescuce teams, immediate medical aid.
• Short-term evacuation of residents
• Tsunami wave breaks and sea walls on coastlines.

Question 13

How can we adapt to the effects of an earthquake?

Answer 13

• Invest in insurance if living in a place at risk.
• Construct infrastructure with earthquake-proof material.
• Construct infrastructure away from high-risk areas.