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