what factors affect risk of hazards
- urbanisation
- poverty
- farming
- climate change
tectonic plates and distribution of volcanoes
- crust is split into 7 major plates
-oceanic crust is dense, thin, younger - continental crust is less dense, thick, older
belts along plate margins (like the ring of fire)
Constructive margin
- 2 plates move apart
- magma forces its way to the surface
- as it breaks the crust, it causes EQ
destructive margin
- 2 plates move towards each other
-dense oceanic plate subducts beneath the less dense, continental plate - friction causes strong EQs
- sinking oceanic plate creates sticky, gas-rich magma
- results in steep-sided composite volcanoes which erupt violently
- where 2 continental plates meet there is no subduction
- the crust crumples and lifts to form mountains
- powerful EQs can be triggered
conservative margin
- 2 plates move past each other at different rates
- friction between plates build stresses and trigger EQ when they slip
- no volcanoes because there is no magma
EQ Nepal, April 2015
Wealth
- LIC
cause
- Indo-Australian plate colliding with Eurasian plate
size
7.9
primary effects
- 9,000 killed
-20,000 injured
- 8,000,000 affected
- destruction of infrastructure
- power, water, sanitation, communications cut
- $5bil damage
- 1.4mil people needed food, water and shelter for weeks
secondary impacts
- communities cut off by landslides and avalanches
- avalanches on Mt Everest killed 19
- flooding caused by landslide blocked rivers
responses in Nepal
immediate
- overseas aid included NGOs like Oxfam
- aid included helicopters for search/rescue and supply drops on remote areas like Everest
- 300,000 people migrated from Kathmandu for shelter/support
- field hospitals set up by organisations e.g. The Red Cross
long-term
- roads repaired, landslides cleared, flood lakes drained
- international conference to seek technical/financial support
- UNESCO is working with the government to restore 700 damaged temples, palaces and museums
EQ Japan 2011
wealth
-HIC
cause
- slippage at the destructive plate margin between North American Plate and Pacific plate
size
9.0
primary impacts
- 3-5 mins of strong ground shaking caused injuries and deaths
- thousands of homes destroyed in Fukushima
- roads and rail lines damaged, electricity, water and sewage disrupted in Tohoku
- 4mil without electricity in north-east
- 1.5 mil without water
- dam burst in Fukushima
secondary impacts
- 10m high tsunami waves
-caused 18,000 deaths and 500,000 homeless
- 560km^2 of coastal land flooded
- waves destroyed infrastructure/ports
- explosions at Fukushima nuclear power plant led to evacuation of 100,000
- $235bil total damage
Japan responses
immediate
- search and rescue teams from Japan and abroad
- 100,000 members of Japanese Self-Defence force
- 500,000 evacuated to high ground before tsunami
- many had homes destroyed and needed emergency shelter, food, water
- roads and railway restored within a few weeks
- power soon restored but supply was intermittent due to explosion
long-term
- reconstruction design council devised long-term plan for the region
- most debris had been cleared by early 2015
- by 2020, 30,000 units of public housing had been completed
- 2013- upgraded tsunami warning system was launched with more accurate forecasts
why do people live at risk of tectonic hazards
- poor people have no choice- money, food, family are seen as more important
- EQs and volcanic eruptions are rare
- EQ-resistant building designs reduce risk
- effective monitoring of volcanoes/tsunami waves allow evacuation warnings to be given
- plate margins often coincide with favourable areas for settlement and trade like flat, coastal areas
- some people have no experience of knowledge of the risks
- volcanoes can bring benefits such as fertile soils, mineral deposits
- EQ fault lines can allow water to reach the surface
Iceland
iceland straddles the Mid-Atlantic ridge with volcanic eruptions every 5 years
- Naturally occurring hot water and superheated steam provides hot water and central heating for 90% of all buildings
- geothermal energy generates 25% of Iceland’s electricity
- volcanic rocks are used in road and building construction
- iceland’s dramatic landscapes with waterfalls, hot springs, lava fields, volcanoes, glaciers support large tourism industry
how can risks from tectonic hazards be reduced?
Monitoring
- volcanoes are monitored using remote sensing, seismicity, ground deformation
- some events may occur before an EQ like microquakes before the main tremor, bulging of the ground, raised groundwater levels
Prediction
- volcano monitoring is now allowing accurate evacuation
- prediction is impossible for EQs but probability can be determined
Protection
- earth embankments/explosive are used to divert lava flows
- EQ drills help keep people alert and prepared, EQ resistant construction
Planning
- Volcano risk assessment and hazard mapping identify areas to practice evacuation/ restrict building
- EQ risk assessment and hazard mapping to identify areas to protect buildings and infrastructure
