Hazard 3: Hazard Risk and Vulnerability Flashcards
How is impacts of tectonic hazards measured?
Impacts of tectonic hazards are measured by damage costs (economic) and deaths and injuries (social). This is because hazards with similar characteristics can have different impacts 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 are also high). Even small costs create problems for poorer people.
Developing countries: incur higher death rates because people are vulnerable; they lack awareness of hazards, live in buildings that have not been proofed, and do not have access to communications, decision-making or emergency services.
What are characteristics and impacts of tectonic hazards that are used in a hazard profile?
- Spatial predictability
- Areal extent
- Frequency
- Magnitude
- Speed of onset
- Duration
How can spatial predictability impact the impacts of tectonic hazards?
Spatial predictability: An area that has never had event will experience greater impacts as people and places will be unprepared.
How can areal extent impact the impacts of tectonic hazards?
Areal extent: The larger the area affected by an event, the greater the impacts will be, as more ppl & places are affected.
How can frequency impact the impacts of tectonic hazards?
Frequency: An event that occurs often is more likely to create cumulative impacts (although rare events have more energy).
How can magnitude impact the impacts of tectonic hazards?
Magnitude: The greater the amount of energy released by an event, the greater the impacts are likely to be.
How can speed of onset impact the impacts of tectonic hazards?
Speed of onset: The faster the events occurs, the shorter the warming time and the greater the impacts as places are unprepared.
How can duration impact the impacts of tectonic hazards?
Duration: The longer an event lasts, the more likely that there will be greater impacts.
How do you compare hazard profiles?
What are the characteristics of events that present the highest risks?
Events that present the highest risks:
-Have high magnitude & low frequencies
-Have rapid speeds of onset with spatial predictability
-Have a large areal extent
-Tend to occur at subduction zones & collision zones.
What is the hazard profile for Haiti and Christchurch earthquakes?
What were the secondary hazards for 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.
Why was the impact so high for Haiti?
- One the poorest countries in the world.
- 54% abject poverty & 20% GDP from remittances.
- 6 months after 98% of rubble remained uncleared.
- 1 in 5 jobs lost.
- 80% of schools destroyed and 25% of civil servants died.
- 2017 – 55,000 still in temporary camps.
- 2 years after, only 43% of aid received.
Why was Christchurch in 2010 & 2011 so at risk from the earthquake? (Hazard)
- Tectonics = earthquake ( transform boundary)
- Geography = epicentre close to Christchurch ( 2010 40km away & 2011 only 10km), focus shallow – 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).
- Secondary hazards: 1st large earthquake in 2010, 11,000 aftershocks continued into 2012, 26 aftershocks were 5+ magnitude and x2 +6 magnitude.
- Trigger Quake: Led to 6.3 magnitude on 22 Feb 2011.
Liquefaction – city built on the edge of Canterbury plains, which are made of loose river deposits. Caused upwelling of 400,000 tonnes of silt. - Seismic lensing: seismic waves travelled through soft rocks and then bounced back of hard basalt rocks, causing further shaking. Landslides & rockfalls – Port Hills
Why was Christchurch in 2010 & 2011 so at risk from the earthquake? (Vulnerability)
- Living conditions = Those living in Port Hills suffered from large rock fall. Many buildings had already been weakened by previous quakes. If is wasn’t for the strong building codes most of 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. Work places & schools had strict emergency plans & emergency services were well prepared.
- 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 revealed after the Darfield 2010 quake. Temporary housing & portable toilets supplied, 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.
- Only vulnerability lied in the living conditions, which was due to the 2010 earthquake having already weakened structures. The city didn’t have the time to strengthen & rebuild before the 2011 quake.
What is the comparison between the Christchurch and Haiti earthquake impacts?
What plate margin is Volcan de Fuego found at and what type of volcano is it?
What was the hazard profile of Volcan de Fuego in 2018?
- 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. Evacuation warning 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 12 mile 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.
What plate margin is Kilauea (Hawaii) found at and what type of volcano is it?
What was the hazard profile of Volcan de Fuego in 2018?
- 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 last eruption similar to current one was 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)
Comparison of Kilauea and Volcan de Fuego hazard profile.
What impacted Volcan de fuego vulnerability?
- Living conditions = 60% lived in poverty and poverty had been rising before the eruption, GDP $8,200. 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 perception & risk low. Residents will have been attracted in to the area due to fertile soils.
- Causes = Poor governance –Government told 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.
What impacted 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 risks of living close to an active volcano. Scientists monitor the rift zones 24 hours a day. Evacuation orders were issued early. Residents encourage to create their own emergency action plan & have somewhere to stay when lava flowing 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.
What was the contrast between Kilauea and Volcan de Fuego impacts?
What were the geographic factors that affected the impact of Volcan de fuego?
- Magnitude: VEI: 4 – Explosive & violent
- Population density & distance: 44km from Guatemala city. Population in 10km radius 54,000 and 30km radius over 1 million.
- Time: 12:00 families separated – shopping at market, playing…. No real evacuation time.
- Secondary hazards: High levels of sulphur lahars ( volcanic mud flows) & landslides have hampered search & rescue efforts
What were the geographic factors that affected the impact of Kilauea?
- Magnitude: VEI 0 Hawaiian eruption, gentle non- explosive
- Population density & distance: located in a national park. But new fissures developing 40km away from the summit.
- Time: Not really relevant as lava slow moving.
- Secondary hazards: High levels of sulphur & Earthquakes caused by the eruption have triggered landslides.
What is the hazard profile Mocoa landslide 2017?
What is the hazard profile Port Hills (Christchurch) Rockfall 2011?
- Timing: 22 Feb 2011, 12:51
- Magnitude: Rockfall - Highly destructive
- Speed of onset: Very quick
- Duration: very short, triggered by earthquake.
- Area affected: Port Hills suburb ( scattered over area 65km squared) by 6,000 boulders.
170 landslides over 150 km squares. - Frequency: Last one 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 epicentre ( suburbs of Christchurch)
- Deaths: 5 dead
Comparison of hazard profile Mocoa and Port Hills.
Green= Port Hills
Blue= Mocoa
What are the impacts of Mocoa landslide?
What are the impacts of Port Hills rockfall?
What are the factors that are affecting the vulnerability of Mocao landslide?
What are the factors that are affecting the vulnerability of Port Hills Rockfall?
- Physical Factors:
Unstable geology due to tectonic processes.
Homes built on steep slopes - Dynamic factors:
2010 earthquake would probably have loosened rocks. - Root causes: Should residents been 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.
