Hazards - Seismic Hazards

Question 1

Describe the nature and distribution of earthquakes?

Answer 1

• Focus – where the release of pressure occurs
• Epicentre – the point above the focus on the surface
• The shallower the focus the more likely it will be powerful whereas a deeper focus would be weaker
• Vast majority occur along boundaries + conservative boundaries e.g. San Adreas Fault
• The magnitude of earthquakes is measured by the Richter Scale

Question 2

What are the primary impacts of earthquakes?

Answer 2

• Ground shaking
• Ground rupture – land that is broken in a line e.g. dams and bridges mostly

Question 3

What are the secondary impacts of earthquakes?

Answer 3

• Liquefaction – when shaken violently, soils with high water content become looser and mudflows can begin
• Landslides and avalanches
• Tsunamis – giant wave caused by tremors resulting in ripples in water, have large catch, before one hits ‘drawdown’ occurs, 90% occur in the Pacific Basin – Example = 2004 Boxing Day Tsunami off Sumatra, killed 350,000 - cost £5billion

Question 4

What mitigation strategies are used in relation to earthquakes?

Answer 4

• early warning systems – it takes time of tsunamis to hit after quakes, in Japan train speed immediately slows and controls lifts
• Resistant Buildings – large concrete movable weight put on top of buildings to move in opposite direction to balance building, shock absorbers in foundations, cross bracing outsides of buildings to hold better
• Tsunami protection – sea walls, seabed pressure sensors attached to buoys to measure changes.

Question 5

How do people adapt to seismic hazards?

Answer 5

• again strongly depends on development)
• Putting key buildings like schools and hospitals in open areas which are low risk
• Include open spaces in town planning away from secondary effects for evacuations.

Question 6

Gorkha Earthquake Nepal 2015

Answer 6

• 7.8 magnitude that was followed by landslides + aftershocks killed 8,800 and destroyed 900,000 homes, 20 people died due to avalanches at Mt Everest basecamp

Planning + Preparation:
- As Nepal is underdeveloped preparation was weak
- Introduced a building code in 1994 + support from UN on disaster management e.g. the Kathmandu declaration in protecting health services from natural disasters

Response:
- £1billion aid from China + India
- Facebook launched safety feature allowing users to indicate safety
- The red cross raised $40million and supplied 130,000 shelters + hygiene kits
- A 4.4million grant from UK government is helping educate people on how to protect themselves in future quakes.