EQ2 - Why do some tectonic hazards develop into disasters? Flashcards
What are the 2 factors which MUST intersect in the Degg Model, to cause a disaster?
- The presence of a natural hazard (e.g Volcano)
AND
- A vulnerable population
Both of these must be present for a disaster to occur
What factors should be considered when understanding risk?
- Unpredictability of events
- Lack of alternatives to the area (e.g occupational immobility)
- Dynamic Hazards (level of threat can increase/decrease over time)
- Cost-benefit of living in a hazardous area
- ‘Russian Roulette Reaction’ (accepting risk - fatalism)
What is the hazard-risk formula?
Risk = hazard x exposure x vulnerability/manageability
Loosely, what is the concept of Resilience?
The ability to ‘spring back’ from a hazard event or disaster shock
What 2 processes form the basis for the Pressure and Release (PAR) model?
Vulnerability
Natural Hazards
What does the creator compare his PAR model to - with the pressures of vulnerability and natural hazards pushing inward to create a disaster
A nutcracker
- this pressure can only be relieved by reducing vulnerability
What 3 components make up progression of vulnerability (PAR) ?
Root Causes»_space;> Dynamic Pressures»_space;> Unsafe conditions
What 3 strategies may be used by resilient communities to limit the affects of a natural disaster?
- Emergency evacuation, rescue and relief systems already in place
- Hazard-resistant building design
- Land-use planning to reduce populations in hazard areas
What is ‘capacity to cope’ with a natural hazard otherwise known as?
Resilience
What is a natural hazard?
Natural events that have the POTENTIAL to harm people and their property
What is a natural disaster, compared to a natural hazard?
A natural disaster is the realisation of the hazard - i.e harm has occurred
What do large insurers define the threshold for a natural disaster?
Where economic losses of over $1.5m are experienced
What demographic factor most affects resilience?
Age
What % of 60+ people live in less-developed regions?
66% - expected to rise to 79% by 2050
What % of those who died in the 2011 Japan tsunami wee 65+?
56%
- although the 65+ demographic did comprise 1/4 of the population in the affected area
What part of the PAR model are these vulnerability factors a part of:
Low access to resources
Poor governance
Weak economic system
Root causes
What part of the PAR model are these vulnerability factors a part of:
Lack of education
Rapid population change and urbanisation
Dynamic pressures
What part of the PAR model are these vulnerability factors a part of:
Poor construction standards
Poverty
Unsafe infrastructure
Unsafe conditions
In Haiti, what were 2 of the main Root Causes of the disaster?
GDP per capita of $350
50% of the population under 20 years old
In Haiti, what were 2 of the main dynamic pressures which caused the disaster?
Lack of disaster education
Rapid urbanisation
In Haiti, what were 2 of of the main unsafe conditions which caused the disaster?
80% unplanned (informal) housing in Port-au-Prince
25% of population live in extreme poverty
What are the 3 broad main impacts of tectonic hazards?
Social, economic and environment
In the last 30 years, which tectonic hazard has had a small and declining impact, especially on death tolls?
Volcanoes
In the last 30 years, which tectonic hazard has had large impacts, with high-magnitude events being common?
Earthquakes
In the last 30 years, which tectonic hazard has been relatively infrequent, but has had very large impacts? (e.g Indian Ocean 2004)
Tsunami’s
Generally, economic costs in developed and emerging countries are often low as their is very little infrastructure.
True or False?
False - costs are often enormous and require large aid sums from developed nations
Death tolls in developed countries are generally low.
True or False?
True - with one exception being Japan 2011 tsunami
What is the name of the updated version of the Richter scale, now used to calculate Earthquake magnitude?
Moment Magnitude Scale (MMS)
What is the name of the type of scale which MMS uses to display earthquake strength?
(e.g where a magnitude 6 earthquake has 10x more ground shaking than a magnitude 5)
Logarithmic scale
What does the older Mercalli scale measure in regard to Earthquakes?
What people actually feel during an earthquake
e.g the intensity of the shaking not just the total energy released
Why can the Mercalli scale not be easily used to compare the severity of an earthquake based on what people ‘feel’?
The shaking people ‘feel’ depends on building quality, ground conditions and other factors
e.g a Mercalli scale VII in Christchurch, NZ may be a scale X in Sichuan, CH - despite being the same magnitude (MMS)
Why might some earthquakes with lower magnitudes still cause significant death tolls?
They can trigger secondary impacts (e.g tsunamis or landslides)
How does the location of an earthquake affect its death toll?
Earthquakes in urban areas have greater impacts than in rural areas due to higher population density
Why might isolated areas experience higher death tolls after an earthquake?
Rescue and relief efforts, including urgent medical aid, take longer to reach these areas
Why might a very high magnitude earthquake cause no death in some cases?
If the earthquakes epicentre occurs in an unoccupied area
What does the Volcanic Explosivity Index (VEI) measure?
The magnitude of a volcanic eruption
What 3 factors combine to create a score of 0-8 on the Volcanic Explosivity Index?
- Eruption Height
- Volume of material released (ash, tephra etc.)
- Duration of eruption
What range on the VEI scale correlates to an ‘Effusive’ eruption?
VEI 0-3
At what 2 boundaries are low magnitude, ‘effusive’ eruptions most common?
- Constructive plate boundaries
- Mid-plate hotspots
What range on the VEI scale correlates to an ‘Explosive’ eruption?
VEI 4-7
At what boundaries are high magnitude, ‘explosive’ eruptions most common?
Destructive plate boundaries
What range on the VEI scale correlates to a ‘Colossal’ supervolcano eruption?
VEI 8+
What is a famous example of a VEI 8+ supervolcano that would bring global cooling if it erupted, with impacts lasting up to 5 years?
Yellowstone
- No modern human has ever experienced the impacts of a VEI 8+ eruption
Which model - with its continuous line format - can be used to compare the nature and associated risks of tectonic hazards?
Tectonic Hazard profile
Why are tectonic hazard profiles useful in comparing tectonic events?
It visualises the differences between each event (e.g duration, speed of onset, magnitude) comparing multiple aspects of a hazard
- This takes into account more relevant factors than purely comparing based on magnitude
With regard to hazard profiles - why do high magnitude, low-frequency events present a high risk?
They are the least ‘expected’ and unlikely to have occurred in living memory
With regard to hazard profiles - what makes rapid onset events with low spatial predictability particularly risky?
They can occur in numerous places without warning, making them harder to prepare for
With regard to hazard profiles - how does regional areal extent, instead of local, contribute to a hazard’s risk level?
It affects a large number of people across a wide range of locations
Why are major earthquakes at subduction zones and collision zones considered the most dangerous tectonic hazards?
Hazard profiles highlight their extreme magnitude (8-9 MMS), unpredictability, and their vast spatial extent (10,000+km) along plate margins
How many people died in Chile 2007 (HDI 0.83) compared to Pakistan 2013 (HDI 0.54) in magnitude 7.7 earthquakes?
Chile = 2 deaths
Pakistan = 825 deaths
How does population growth increase risk during tectonic hazards?
Leads to more people in vulnerable areas, and a strain on resources
How does urbanisation and sprawl increase risk?
Creates dense settlements, often informal housing with no building regulations
How does environmental degradation increase risk?
Removes natural defences to hazards (e.g mangrove deforestation in Indian Ocean 2004)
How does loss of community memory about hazards increase risk?
People are less aware of the hazard and therefore are less prepared and slower to respond
How does a very young or elderly population increase risk?
They are less able to evacuate easily and independently. This can also put caregivers at increased risk.
How does outdated infrastructure increase risk?
Less resilient to hazards, increasing the likelihood of collapse
How does reliance on power, water and communications increase risk?
Can disrupt essential services, limiting rescue and recovery efforts
(e.g power and water outages for weeks affected 80% of Christchurch in 2011)
How do warning and emergency-response systems mitigate risk?
Provide alerts and pre-planned responses, reducing casualties and damage
How does economic wealth mitigate risk?
- Higher quality resilient infrastructure
- Quicker recovery
- Better response systems
How do government disaster-assistance programmes mitigate risk?
Provide financial aid, relief services and resources immediately
How does insurance mitigate risk?
Helps individuals and businesses recover financially
How do community initiatives mitigate risk?
Promote development of response plans and risk awareness
How does scientific understanding mitigfate risk?
Improves hazard prediction and early warning systems for evacuation
How does hazard engineering mitigate risk?
Structures are designed to withstand natural hazards, reducing damage and casualties
Natural disasters affect everywhere equally. Areas of low development will feel the same impacts as areas of high development.
True or False?
False - areas of low development are initially much more vulnerable
Why is vulnerability high in areas with very low development (below 0.55 HDI)?
Even in normal times, people lack basic needs such as sufficient water and food
How does informal housing contribute to high vulnerability in low-development areas?
Housing is built with no regard for hazard resilience, increasing risk of collapse during a disaster
How does limited access to healthcare increase vulnerability in low-development areas?
Leads to higher rates of disease and illness, making populations less able to survive during natural disaster
Why does lower education increase vulnerability in low-development areas?
Leads to lower hazard perception and risk awareness, meaning people are less prepared
What % of families lived below the poverty line during the Nepal 2015 earthquake?
40%
What % of families depended on subsistence farming during the Nepal 2015 earthquake, and why was this problematic?
Over 90% - many starved to death as crops were destroyed during the earthquake
What % of the rural population of Nepal were malnourished in 2015 earthquake, and why was this problematic?
Many had stunted growth and were physically too weak to survive the impacts of the earthquake
What % of rural Nepal was literate during the 2015 earthquake, and why was this problematic?
20-40% were literate - this reduced their ability to understand disaster warnings
How does the effectiveness of governments impact resilience during a natural disaster?
Government and policies influence a places coping capacity, and determines how well a community can prepare and respond to disasters
How is a well-governed country - one which meets basic needs (food, water, healthcare etc.) - more resilient to natural disasters?
By meeting food, water and health needs, a population is physically more able to endure/survive a natural disaster
How does effective land-use planning reduce disaster risk?
Prevents habitation in high-risk areas
(e.g on unstable slopes, liquefaction areas)
How does a government with good environmental management reduce vulnerability to secondary hazards?
By preventing degradation (e.g deforestation) secondary hazards such as landslides are less severe
How do government-supported education programs reduce disaster risk?
Teaches people how to prepare, evacuate and respond during disasters
How does corrupt governance affect vulnerability to a natural disaster?
Corruption - such as mismanagement of funds or bribery - may mean less focus is on effective disaster management and unsafe building practice
How does government openness and accountability increase resilience to natural disasters?
More effectively able to convey disaster warnings (e.g through the media) to their population and are considered more trustworthy
How do government-supported disaster management agencies (non-profits) increase resilience?
Agencies (such as FEMA) require funding from the government (as they are non-profits) to ensure they can co-ordinate effective disaster responses
How can good governance reduce the vulnerability of high population densities in tectonic hazard areas?
Evacuation plans and zoning laws
(e.g Naples surrounding Mt. Vesuvius)
Why are urban areas with more government assets likely to be more resilient during disasters?
They are likely to have well-stocked hospitals and good transport links in the event of disaster
When were the earthquakes in Christchurch, NZ? (developed)
Began late 2010, with the most destructive shock in Feb 2011
When was the 7.0 magnitude earthquake in Port-au-Prince, Haiti? (developing)
2010
What were the focal depths for Christchurch and Haiti respectively?
Christchurch = very shallow (5km)
Haiti = relatively shallow (13km)
For how long had the Enriquillo-Plaintain Garden Fault been locked, prior to Haiti 2010?
250 years - creating substantial pressure
How many people died in Christchurch 2011 compared to Haiti 2010
Christchurch = 185 killed
Haiti = 300,000 killed
(300,000 more also injured in Haiti)
How many homes were demolished in Christchurch 2011 compared to Haiti 2010?
Christchurch = 1000
Haiti = 105,000
For how long did schools close in Christchurch 2011?
2 weeks
What % of people temporarily left Christchurch in the immediate aftermath of the 2011 earthquake?
Around 1/5
- only 5-8% of the previous total population of Christchurch left permanently after the event
50% of what type of public sector buildings were entirely destroyed by the Haiti 2011 earthquake?
50% of all hospitals/healthcare buildings
What deadly waterborne disease broke out in Haiti by November 2010?
Cholera
What were the respective % of GDP which damages related to earthquakes accounted for in Christchurch 2011 and Haiti 2010?
Christchurch = 20% of GDP ($28bn)
Haiti = 120% of GDP (around $8bn)
Why was the economic shock in Christchurch 2011 less significant than in Haiti 2010, despite higher losses? ($28bn vs $8bn)
New Zealand had a stronger economy to deal with the shock than Haiti
- whilst Christchurch’s losses were greater in absolute terms ($28bn), the economic shock was less severe than in Haiti ($8bn)
Long term, what % of Haitians lost their job following the 2010 earthquake?
20%
