Hazards 3- Case studies Flashcards
What are the different impacts of hazards on developed and developing countries?
Developed countries:
-Incur higher damage costs because there are more expensive buildings and infrastructure to be damaged (insurance and repair costs also high).
-Even small costs create problems for the poor.
Developing countries:
-Incur higher death rates because people are more vulnerable, lack awareness of hazards, live in buildings that haven’t been proofed, and don’t have access to communications, decision-making, or emergency services.
Hazard event profile for Haiti and Christchurch earthquakes
Characteristics and impacts of tectonic hazards
-Spatial predictability: An area that has never had an event will experience greater impacts as people and places will be unprepared
-Areal extent: The larger the area affected by the event, the greater the impacts will be, as more people and places will be affected
-Frequency: An event that occurs often is likely to create cumulative impacts (although rare events will have more energy)
-Magnitude: The greater the magnitude of energy released by an event, the greater the impacts are likely to be
-Speed of onset: The faster the event occurs, the shorter the warning time and the greater the impacts as places are unprepared
-Duration: the longer an event last, the more likely that there will be greater impacts
What are the characteristics of events that present the highest risks?
-Have high magnitude and low frequencies
-Have rapid speeds of onset with spatial predictability
-Have a large areal extent
-Tend to occur at subduction zones & collision zones.
The Pressure and Release (PAR) model
2010 Haiti Earthquake- tectonics and geography
Tectonics = earthquake (conservative boundary)
Geography:
-Epicenter close to capital Port au Prince (25km away), focus shallow (only 13km)
-Spatial extent quite large (120km2)
-Hadn’t experienced an earthquake in 150yrs, so no experience,
-Magnitude 7,
-Speed of onset = sudden ( 30-60 seconds),
-Predictability: none (known fault).
2010 Haiti earthquake secondary hazards
-Over 45 aftershocks > 4.5 and two aftershocks of 5.9 and 5.5 within a few days and 5.9 on the 20 January.
-One town experienced a localized tsunami
-Liquefaction in the port area.
2010 Haiti earthquake- living conditions and pressures
-Living conditions = Buildings & infrastructure not earthquake-proof, high unemployment, relied on the informal sector, many lived in slums, 72% lived in poverty, homes built on slopes.
-Pressures = rapid rural to urban migration, growth of slums..all put pressure on local authorities. Hillsides stripped of trees to make more space. Low HDI. Education levels are lower, so perception & risk were low.
2010 Haiti earthquake- contribution of poor governance
-Basic needs were not being met -limited access to roads, electricity & sanitation.
-Poor planning – deforestation & building on hillsides, no preparedness, didn’t ensure correct building codes, corrupt government.
-Access to health care & education is poor.
-Low-income groups lack a ‘safety net’ after a disaster – personal one ( savings, food) or government one ( social security, aid, free healthcare)
Statistics about Haiti in 2010
-One the poorest countries in the world.
-54% abject poverty & 20% GDP from remittances.
-6 months after the event, 98% of the rubble remained uncleared.
-1 in 5 jobs lost.
-80% of schools were destroyed and 25% of civil servants died.
-2017 – 55,000 still in temporary camps.
-2 years after, only 43% of aid was received.
When was the Haiti earthquake?
2010
When were the Christchurch, New Zealand, earthquakes?
2010 and 2011
Christchurch earthquake tectonics and geography
Tectonics = earthquake (conservative boundary)
Geography:
-Epicentre was close to Christchurch (2010- 40km away & 2011 only 10km),
-Shallow focus – only 10km in 2010 and 5km in 2011
-Spatial extent 12km2
-Earthquakes normally occur every 55 yrs
-Magnitude 7.1 & 6.3
-Speed of onset = sudden ( 30-60 seconds),
-Predictability: none ( 100 faults in the area, margin complex/changing).
Christchurch earthquakes- secondary hazards
1st large earthquake in 2010, 11,000 aftershocks continued into 2012, 26 aftershocks were 5+ magnitude and x2 +6 magnitude.
Christchurch earthquakes- trigger quake
-Led to 6.3 magnitude earthquake on 22 Feb 2011.
-Liquefaction in the city built on the edge of Canterbury plains, which are made of loose river deposits.
-Caused upwelling of 400,000 tonnes of silt.
Christchurch earthquake- seismic lensing
-Seismic waves travelled through soft rocks and then bounced back of hard basalt rocks, causing further shaking
Christchurch earthquakes- living conditions and pressures
Living conditions
-Those living in Port Hills suffered from large rock fall.
-Many buildings had already been weakened by previous quakes.
-If it wasn’t for the strong building codes, most of the city would have been flattened due to shaking & liquefaction.
Pressures
-Didn’t experience the extra pressures like Haiti.
-Schools had been carrying out regular drills ‘the turtle) since the 2010 earthquake.
-Workplaces & schools had strict emergency plans & emergency services were well prepared.
Christchurch earthquakes- causes
-Didn’t suffer from poor governance or from a weak economy or cultural issues.
-NZ is well prepared for earthquakes, but the Greendale fault was unknown until it was revealed after the Darfield 2010 quake.
-The only vulnerability lay in the living conditions, which was due to the 2010 earthquake had already weakened structures. The city didn’t have the time to strengthen & rebuild before the 2011 quake.
Christchurch earthquakes- responses
-Temporary housing & portable toilets were supplied, a full emergency plan was in place within 2 hours.
-Vulnerable people were well looked after. Schools amalgamated to ensure provision continued. Farmers helped to remove rubble.
Hazard profile for Haiti 2010 and Christchurch 2011
Table comparing the impacts of Haiti and Christchurch earthquakes
When was the Volcan de Fuego eruption?
2018
Vulcan de Fuego type of margin
Destructive
Vulcan de Fuego plate margins diagram
Need info about destructive margins?
Composite volcano diagram
Volcan de Fuego eruption features
-Magnitude: VEI 4 – explosive nature, but characteristics of Plinian (eruption column over 10km) & thus severe.
-Speed of onset: Monitored by vulcanologists, but the build-up of energy caught scientists by surprise. An evacuation warning was given 8 hours in advance.
-Duration: Major explosions lasted 16 hours. Small eruptions almost every 20 days & has been very active since 2002.
-Areal extent: Ash spread over a 19 km radius. Pyroclastic flow spread 10 km
-Spatial predictability: Predictable – Pacific Ring of Fire & know the location.
-Frequency: Erupting every 20 days ( small), erupted 60 times since 1524. Last major eruptions 1932, 1974 & 2012.
Typical volcano hazard profile
When was the volcanic eruption in Kilauea, Hawaii?
Diagram of shield volcano
Diagram of Hawaiian hotspot
Need info about hotspots?
Kilauea eruption features
-Magnitude : 0 on the VEI – Hawaiian eruption, non-explosive
-Speed of onset: Quite slow & the fastest lava is only moving at around 17mph ( slightly faster than a running man). Generally can walk away from the lava.
-Duration: Long, been active since 1983 and the last eruption similar to the current one was in 1955, where it lasted 88 days.
-Areal extent: Covers 9.4 square miles (June 18)
-Spatial predictability: Predictable – we know where the mantle plume is.
-Frequency: Very frequent, been erupting for 35 years & currently has been spewing lava for over 3 months (Aug 2018)
Volcan de Fuego- vulnerability
-Living conditions = 60% lived in poverty and poverty had been rising before the eruption, GDP $8,200. The area around the volcano –rural – rely on agriculture. Little training as to what to do if the volcano erupts.
-Pressures = Low HDI. Education levels are lower, so the perception of risk was low. Residents will have been attracted to the area due to fertile soils.
-Causes = Poor governance –The government told people to evacuate people 7 hours before the eruption, but they did not act. Education was poor, people were not prepared. Low-income groups lacked a ‘safety net’ after the disaster, as did the government - debt 30% of GDP. Allowed villages to develop in the foothills of a violent volcano. Only one seismometer monitoring the volcano.
-High corruption rates.
Table constrasting the geographic factors affecting the impacts of Volcan de Fuego and Kilauea
Table contrasting the impacts of Volcan de Fuego and Kilauea
Kilauea- vulnerability
-Living conditions = Buildings & infrastructure are earthquake-proof, wealthy nation.
Many islanders don’t have volcano insurance.
Tourist numbers fell with the island losing $5mn May – June.
-Good governance – Residents well versed in the risks of living close to an active volcano. Scientists monitor the rift zones 24 hours a day. Evacuation orders were issued early. Residents were encouraged to create their own emergency action plan & have somewhere to stay when lava flows near their residency.
-Evacuation plan was put in place immediately and an emergency disaster centre was set up to support residents.
-Those who lost homes entitled to $34,000 in federal aid.
When was the Mocoa Landslide?
2017
Table showing the features of the Mocoa landslide
Typical landslide hazard profile
Typical volcano hazard profile
Hazard profile for Macoa landslide (blue) and Porthills rockfall (green)
When was the Port Hills (Christ Church) rockfall?
2011
Features of Port Hills rockfall
-Timing: 22 Feb 2011, 12:51
-Magnitude: Rockfall - Highly destructive
-Speed of onset: Very quick
-Duration: very short, triggered by the earthquake.
-Area affected: Port Hills suburb (scattered over an area 65km squared) by 6,000 boulders.
170 landslides over 150 km squares.
-Frequency: Last one was 7,000 years ago, so not all earthquake events have triggered them.
-Predictability: Risks still high today – future earthquakes, rainfall….. 400 homes were initially deemed unhabitable due to future rockfall risk.
-Proximity: Only 7km from epicenter ( suburbs of Christchurch)
-Deaths: 5 dead
Impact of the Port Hills rockfall
Impact of Mocoa landslide
here is Port Hills?
New Zealand (suburb of Christchurch)
Where is Mocoa?
Putomayo, Colombia
Vulnerability factors affecting the Port Hills rockfall
Physical Factors:
-Unstable geology due to tectonic processes.
-Homes built on steep slopes
Dynamic factors:
The -2010 earthquake would probably have loosened rocks.
Root causes:
-Should residents be allowed to build on steep slopes in an earthquake-prone area?
-It had been identified for potential landslides & rockfalls in 1977 by the Environmental Agency & then by Engineering Lifelines in 1997.
Vulnerability factors affecting the Mocoa landslide
