Tectonic hazards and disasters Flashcards
What is the difference between a hazard and a disaster?
A hazard is the perceived natural/geophysical event that has the potential to threaten both life and property. For a hazard to be a hazard, it has to affect life and property.
A disaster is the realisation of a hazard, when it ‘causes a significant impact on a vulnerable population’.
Why may people choose to live in areas with high-risk of natural disaster?
1 - UNPREDICTABILITY - many hazards are predictable, but some, such as earthquakes, aren’t. People may simply be caught off guard by the timing, location and magnitude of an event.
2 - LACK OF ALTERNATIVES - people may stay due to lack of other options. This may be due to favourable employment, lack of space to move, or lack of skills, knowledge and/or resources.
3 - DYNAMIC HAZARDS - threat of hazards may decrease or increase subtly over time. Human influence may also change the likelihood and location of hazardous events.
4 - COST-BENEFIT - the benefits of a hazardous region may outweigh the risks involved in staying. Volcanic soils have high nutrient contents, meaning farmers may decide to ‘bite the bullet’ and set up near a volcano. Perception of risk plays a part in cost-benefit analysis.
5 - ‘RUSSIAN-ROULETTE REACTION’ - the acceptance of the risk as something that will happen whatever you do, with little care given to mitigation.
What is the hazard-risk formula?
Risk = hazard x exposure x (vulnerability/manageability)
Define “resilience”
Resilience is the ability of a system, community or society exposed to hazards to resist, absorb and recover from the effects of a hazard.
What is the ‘Pressure and release model’ (PAR model)?
The idea that a disaster is the intersection of two processes; processes generating vulnerability on one side and the natural hazard event itself on the other.
Progression of vulnerability is split into three segments: Root causes, dynamic pressures and unsafe conditions.
What are the three earthquake scales, and what do they measure?
RICHTER SCALE: 0-10, a measure of the amplitude of waves produced by earthquakes. The Richter scale is an absolute scale, two 5.0s will always be the same on the Richter scale.
MODIFIED MERCALLI SCALE: I-XII, measures the impacts experienced from an earthquake. A relative scale, based on damage to structures.
MOMENT MAGNITUDE SCALE (MMS): 0-9, a modern measure used by seismologists to describe earthquakes in terms of the energy that they release. Calculated from the amount of slip produced by an earthquake, the area affected and an Earth-rigidity factor. This is used by the USGS.
On what scale are volcanic eruptions measured?
The VEI scale, Volcanic Explosivity Index, a relative measure of the ‘explosiveness’ of an eruption, which is calculated from the volume of ejecta. The VEI scale is, like MMS and Richter scale, logarithmic.
What are tectonic hazard profiles?
A technique used to try to understand the physical characteristics of a seismic hazard. Hazard profiles can be used to analyse and assess contrasting hazards. Some criteria often included are; frequency, duration and time of onset.
What was a secondary impact of the 2010 Haiti Earthquake that caused the deaths of 10,000 people?
Severe cholera outbreak. Broken pipes caused sewage to seep into freshwater reserves, wells and faucets, spreading the disease amongst the populace.
What is the ‘risk-poverty nexus’?
The idea that inequality has multiple dimensions in how a population deals with a disaster.
1 - Asset inequality (Housing, security and agricultural productivity)
2 - Inequality of entitlements (Unequal access to public health services)
3 - Political inequality (unequal capacities and authorities)
4 - Social status inequality (informal settlements)
What factors may influence hazard vulnerability?
Quality of governance (corruption in Haiti)
Population density (number of people affected by a disaster increases)
Geographic isolation and accessibility (slower aid arrival)
Degree of urbanisation (less developed infrastructure)
What factors made the 2003 Bam, Iran earthquake so destructive and deadly?
1- SHALLOW, the hypocentre was just 7km below the surface.
2- TIME, the earthquake occurred at 5:26am, most people asleep indoors
= little time to react.
3-SEISMIC WAVES, thought to be vertical, causing max. damage to
buildings.
4- VULNERABLE BUILDINGS, some buildings 2,400 years old, very
fragile.
5- POOR QUALITY INFRASTRUCTURE, buildings were especially
vulnerable.
What is the Swiss-cheese model?
The concept that one method of protection will have flaws that allow hazards to manifest into losses, however multiple layers of protection reduce the chance of hazards manifesting into losses.
