D.2 - Geophysical Hazard Risks Flashcards
Define hazard
-Any threat which can cause loss of life, injury, property damage, environmental degradation
etc.
-Has the potential to affect people
Define hazard event
• The occurrence of a hazard which has negative impacts
• Accompanied by the resulting demographic/economic/environmental conditions
Define hazard perception
• The degree to which a hazard is considered a threat by different people
Define resilience
• The ability to protect lives/infrastructure from destruction and recover after a hazard event
Define adaptation
• Altering human actions to account for increasing hazard risks
Define geophysical hazard
• A hazard associated with the earth’s processes
Define disaster
• Major hazard events that cause widespread disruption to a community/region
• Lead to significant demographic/economic/environmental losses
• Affected community is incapable of dealing with it adequately without outside help
Where are volcanos found
Concentrated along convergent plate boundaries where subduction occurs
Can also be found at divergent plate boundaries or above a hot spot
Where are earthquakes found
Found at all three plate boundaries
The most hazardous ones occur at convergent boundaries
Where are tsunamis found
Begin near the epicentre of EQs, then radiate outwards far along ocean waters
Where is mass movement found
Result of gravity
Most likely to occur on steep hills, especially with heavy rainfall, frequent freeze-thaw, snowfall, and limestone rocks
Define risk management
- Identifying, assessing, and prioritising risks
- Allocating resources in effective coordinated manner to reduce potential hazards
- To be effectively implemented, requires the measurement of the magnitude, frequency, and likely recurrence of hazards
What are 2 ways of measuring earthquakes
- Richter scale
- modified mercalli intensity scale
What is the Richter scale
Most common method
Measures amount of seismic energy released in an EQ
Uses a logarithmic scale from 0-10+
A difference of one represents an approximate thirtyfold difference in magnitude
EQs measuring 5+ can cause destruction
Over 7 will cause major damage if near settled areas
Allows easy comparison of EQ magnitudes, regardless of the location
What is the modified mercalli intensity scale
Designates Roman numerals to represent EQ intensity, ranging from imperceptible shaking to catastrophic destruction
No mathematical basis
Uses arbitrary rankings based on observed effects
E.g. if furniture moves, if buildings collapse, if people are frightened
Can be useful as its descriptions can be related to observations
However, useless in places without trees, houses, railways etc.
Can also be variable, depending on personal interpretations
How are the volcanos formed
The volcanoes in the Pacific Rim or Ring of Fire are caused by the subduction beneath either the oceanic or continental crust. Subduction in the oceans provides chains of volcanic islands known as island arcs, such as the Aleutian Islands formed by the Pacific Plate subducting beneath the North American Plate. Where the subduction of an oceanic crust occurs beneath the continental crust, voung fold mountains are formed. The Andes, for example, have been formed where the Nazca Plate subducts beneath the South American Plate.
Where are most volcanos found
The pacific ring of fire
Where a landslides most likely to occur
Landslides are naturally occurring phenomena in every environment on Earth, including the tropics, the temperate regions, the high latitudes and also the ocean. However, fatal landslides tend to be more common in areas that have:
active tectonic processes that lead to high rates of uplift and occasional seismic events
• high levels of precipitation, including high annual totals and high short-term intensities
• a high population density.
define risk
The probability of a hazard event causing harmful consequences
Define disaster risk
Consequence of interaction between a hazard and the characteristics that make places vulnerable
Define vulnerability
• The characteristics of a community that make it susceptible to damage from hazard events
• Rich countries are more vulnerable to economic costs
• Poorer countries are more vulnerable to social costs
Define capacity
• Ability for a community to absorb and ultimately recover from a natural disaster
• E.g. hazard mapping, early warning systems, effective communication, availability of emergency response
What are 5 ways of measuring risk
- disaster recovery index
- disaster deficit index
- local disaster index
- prevalent vulnerability index
- risk management index
What is disaster recovery index
Estimates risk of loss of life
Ignores possible damage to livelihoods and the economy
Considers the hazard, population size, and the vulnerability of the population
Good at clearly highlighting hazard risk and avoiding problems when comparing countries with fluctuating currency exchange rates
However, estimating number of deaths is difficult, and doesn’t measure gov’t capacity to improve state of development to reduce risk
What is disaster deficit index
Models consequences of hazard events in macroeconomic and financial terms
Represents maximum probable loss, and capacity of country to deal with it Informs if governments will be able to raise sufficient funds to cope with losses
What is local disaster index
Measures social environmental risks at a local scale
Particularly looks at those with a greatest impact on poorer people
What is prevalent vulnerability index
Composite measurement based on indicators for exposure, socio-economic fragility, and resilience
However, requires more data which may be difficult to gather in poorer countries
What is risk management index
Composite measure based on indicators of risk identification/reduction, hazard reduction, and effectiveness of governance
Estimates risk management in terms of institutional organisation, capacity, and development to reduce losses
What is troubling about analysing risks
• Insurance companies try to analyse and predict hazards in a very detailed manner
• However, errors can occur
• Challenging due to the many variables and different time scales to consider (e.g. both direct and indirect effects)
• Can often be misjudged as planners underestimate the severity or frequency of hazards, for a variety of reasons
What three reasons make it troublesome to analyse risks
- economically poor countries
- lack of data
- psychological denial
Why are hazards in economically poor countries difficult to analyse
Gov’ts may deliberately minimise severity of hazards to spare certain companies the expense of dealing with the remedies required
Why does the lack of data make hazards difficult to analyse
People may lack the necessary long-term data and information to accuratelv assess risk
Why does psychological denial make it difficult to analyse hazard s
People may understand the risk but psychologically suppress it so the benefits of living in the area are not challenged
What are 2 social reasons people live in hazardous environments
- must live where they are born
Due to extended family ties, being in debt to a landlord, lack of finances to move - they do not realise there is a hazard where they live
e.g. EQs can strike in places with no prior history of EQs
What are 4 economuc reasons people live in hazardous environments
- fertile soils near active volcanos
Volcanoes erupt and distribute ash which aids the fertilitv of soils
Good for cultivation - employment
Farmers may lack skills required to gain employment if they moved to urban areas - living costs
Hazardous areas cost less to live in - tourism
Wild, raw, barren volcanic landscapes can attract tourists
What are 7 social factors affecting geogphysical hazard risks
- less education
- gender
- remoteness and isolation
- building type
- children
- higher population density
- large amounts of recent arrival
How does less education create more hazard risk
Less likely to recognise dangers of living in hazard areas
Less able to take preventative action e.g. in wealthier and educated countries like
Japan and USA, students routinely practice EQ drills to prepare for hazards
How does gender create higher risk of hazard
Tend to have less access to resources, and be the main caregivers
Less able to respond to disasters with the resources needed to
How’d ones remoteness and Isolation create geophazard risks
Rescue services take longer to reach the site Communications may be less reliable, with less developed telephone/internet links
Often have less well-equipped hospitals and emergency centres, requiring injured to be transported long distances for treatment
How does building type create geophysical hazard risk
Lower buildings are more susceptible
Taller buildings are typically more flexible and thus safer
How dies children make a area more affect by geophysical hazards
Vulnerable to long-term psychological problems as they can’t fully understand what is happening
Can be vulnerable to disease and death if infections break out
how does a higher population density make you more vulnerable to geophysical hazards
More difficult evacuations
More difficult to get rescue crews into these areas
How does large amounts of arrival make a area more affect by geophysical factors
Less likely to know their way around, making evacuation less efficient
Less likely to know about potential geophysical hazards
What are 3 economic factors affecting geophysical hazard risk
- cheap housing
- poorer countries
- wealthier countries
How does cheap housing affect geophysical hazard risk
Many poor people live in shanty settlements which lack basic facilities like clean water, drainage, and telecommunications
They are also often built in high-risk locations, near steep valley sides, flood-prone rivers, and on fault lines of tectonic plates
How do poorer countries create geophysical hazard risk
Technology is often inadequate
Harder to pay for early warning systems to warn of impending risks
Building standards are often low to save funds or due to corruption between building developers and gov’t officials
Thus, many structures are damaged and can possibly trap people inside
Tend to have poorer emergency services with less personnel
e.g. relief workers may work with shovels compared to ultrasound search devices, ambulances, and excavation equipment etc.
Worse education, poorer funded gov’t agencies, less money to pay for repairs, less change of back-up communication lines
Less likely to have insurance coverage against disasters, to repairs take longer to be made
How does wealthier countries affect geophysical hazard risks
Infrastructure is likely to have greater financial value with higher construction costs and greater levels of services provided
Tend to have assets with higher cash values which cost more to repair
Thus, hazard events will have greater financial costs (although damage typically represents greater proportions of total wealth in poorer countries)
What are 2 political factors affecting geophysical hazard risk
- political conflict
- political structure
How does political conflict affect geophysical hazard risk
Civil unrest and conflict can impede rescue efforts
e.g. frequent EQs/mass movements in
Afghanistan
How does political structure affect geophysical hazard risk
Can be a barrier to mounting effective rescue events
e.g. Chinese government in 1970s routinely practiced secrecy, so EQs were reported days after occurring, delaying initial rescue and recovery efforts
What are 4 factors affecting geophysical hazard event impact
- physical location
- time of days
- urban areas
- rural areas
- population density
- rock type and sediment
- economic development
How does physical location affect geophysical hazard event impact
Places found on plate boundaries have higher risks of experiencing EQs or eruptions
Locations on steep mountain sides are more likely to experience mass movement events
how does time of day affect geophysical hazard event impact
Hazards that strike at busier times of day often cause more deaths and injuries
More people are out in the streets, away from familiar areas
Congested streets make it more difficult for rescue vehicles to move around and help victims
how does urban areas affect geophysical hazard event impact
More vulnerable to falling walls and collapsing buildings
How does rural areas affect geophysical hazard event impact
More vulnerable to landslides as unstable slopes are less likely to have been stabilised and strengthened
They have fewer rescue services to respond
How does pop;latino density affect the impact of a geophysical event
a geophysical event that hits an urban area of high population density, such as in the Tokyo area of Japan, could inflict far more damage than one that hits a rural area of low population and building density. Most of the deaths in the 1985 Mexico City earthquake occurred in the city, despite the focus being over 200 km away.
How does building type affect the impacts of geophysical events
high-income countries generally have better-quality buildings that have been built to be earthquake resistant.
The 2010 Port-au-Prince earthquake destroyed more buildings than the 2010-2011 New Zealand earthquakes although they were of comparable magnitude. People in high-income countries are also more likelv to have insurance cover than those in low-income countries, so recovery after the event is easier.
How does rock type and sediment affect the impacts of geophysical hazards
loose materials may act like liquid when shaken, a process known as liquefaction. Solid rock is much safer, and buildings built on flat areas of solid rock are more earthquake resistant. Unconsolidated volcanic sediments are at high risk of landslide compared with solid geology, for example the Casita volcano in Nicaragua following Hurricane Mitch.
How does economic development affect the impacts of geophysical events
Economic development: high-income countries will generally have a better level of preparedness and more effective emergency response services, better access to technology and better health services. There will be more funds to cover the cost of coping with disasters. The responses to the Christchurch earthquakes in New Zealand were more effective than the responses to the Port-au-Prince earthquake in Haiti.
How does construction styles and building codes affect the vulnerability of a area to geophysical hazards
Construction styles and building codes: there was criticism during the Sichuan earthquake that whereas government buildings remained standing many schools were destroyed (suggesting that the schools were poorly built).
How does access to technology affect the vulnerability of an area to a geophysical hazard
Access to technology: in Japan, earthquake and tsunami warnings are issued to people via smartphones; people with greater access to communications are better able to keep up to date with warnings and forecasts.
What are some demographic factors that affect the vulnerability of an area to geophysical hazards
• Population density: a large number of rapidly growing cities are in hazardous areas; large urban areas such as Port-au-Prince in Haiti are especially vulnerable to natural hazards
• Age: 65 per cent of those who died in the Japanese tsunami in 2011 were aged over 60.
• Migrants: when people move to an area they may be unaware of some of the natural hazards present in that environment.
• Disability: the mortality rate of the disabled in the Japanese tsunami of 2011 was twice that of the normal population.
• Cultural factors: some of the cultural factors that influence public response to warnings are: the extent of trust in government, scientists or other authority figures; the extent and success of social networks; the amount of control or autonomy that a community feels it has; and the perceived hazard level.
What is the recurrence interval or return period
The recurrence interval or return period is the expected frequency of occurrence in years for an event of a particular size. In general, small events have a high frequency/short return period whereas large events have a very low frequency/high return period. Thus there are fewer highly destructive earthquakes but many minor ones (Table D.3 and Figure D. 14). These are generalized into high-frequency/low-magnitude events versus low-frequency high-magnitude events. Low-frequency high-magnitude events cause the most destruction and require the greatest management.
