Option Theme - Hazards and Disasters Flashcards
Disaster
A major hazard event that causes widespread disruption to a community or region that the affected community is unable to deal with adequately without outside help
Hazard
A threat (natural or human) that has the potential to cause loss of life, injury, property damage, socioeconomic disruption or environmental degradation
Hazard event
The occurrence (realisation) of a hazard, the effects of which change demographic, economic and/or environmental conditions
Risk
The probability of a hazard event causing harmful consequences (expected losses in terms of deaths, injuries, property damage, economy and environment)
Vulnerability
The susceptibility of a community to a hazard or to the impacts of a hazard event
Areal extent
The size of the area covered by the hazard
Small scale (avalanche) to continental (drought)
Spatial concentration
Distribution of hazards over space, whether they are concentrated in certain areas (tectonic plate boundaries, coastal areas)
Speed of onset
Time difference between the start of an event and the peak of an event
Rapid events (Kobe earthquake)
Slow timescale events (drought in the Sahel)
Regularity
Some hazards are regular (e.g. tropical cyclones) whereas others are random (e.g. earthquakes)
What is the focus?
The focus refers to the place beneath the ground where the earthquake takes place
What are deep-focus earthquakes ?
Deep-focus earthquakes are associated with plate margins where the oceanic plate is forced under the continental plate, in a process know as subduction
Where are shallow-focus earthquakes generally located?
Shallow-focus earthquakes are generally located along constructive and conservative boundaries
What is the epicentre?
The epicentre is the point on the ground surface immediately above the focus
What types of human activities cause earthquakes?
- nuclear testing
- building large dams
- drilling for oil
- coal mining
How are earthquakes caused at conservative boundaries?
As plates slide past each other, friction between them causes earthquakes. These are rare but very destructive
How are earthquakes caused at constructive boundaries?
Earthquakes are caused by friction as the plates tear apart. These earthquakes are small and don’t do much damage
How are earthquakes caused at destructive boundaries?
Sinking oceanic plate can stick to the continental plate. Pressure builds up against the friction. When the plates finally snap apart a lot of energy is released as an earthquake. They can be devastating, especially if shallow
Give an example of a conservative plate boundary
The San Andreas Fault
Why are tectonic hazards increased in developing countries?
People live in risky locations as there’s nowhere else to live
Can’t afford safe well-built homes so often buildings collapse
They don’t have insurance
Governments don’t have money and resources to provide aid
Poor communications so warning and evacuation may not happen
What are the focus and epicentre of an earthquake?
An earthquake starts at the focus. The epicentre is the point on the Earth’s surface above the focus and is the first place to shake
What happened in the Nigata (Japan) earthquake in 2007?
In city of 90,000, 11 people died + 1000 injured
350 buildings destroyed
Tsunami warning issued but false alarm
Epicentre offshore so less shaking on land
Happened at 6pm - people alert and remembered drill
What happened in the Kobe (Japan) earthquake in 1995?
City of 1.5 million - very high population density
5000 died and 26,000 injured
Many fires started and couldn’t be reached due to collapsed buildings
Damage was $200 billion
Epicentre was close to Kobe
Happened at 6am - people were asleep and confused in the dark
Name 3 features of earthquake contingency planning in Japan?
Every year Japan has earthquake drills
Emergency services practise rescuing people
People keep emergency kits at home containing water, food, a torch and radio
Name 6 features of an earthquake proof building in a developed country
Damper in roof acts like pendulum reducing building sway
Shock absorbers built into cross braces
Strong double glazed windows stop broken glass showering down
Very deep foundations to prevent collapse
A strong steel flexible frame prevents cracking
Cross bracing stops floors collapsing
When and where did the Sichuan earthquake occur?
In a province in central China on 12 May 2008
What were the primary impacts of the Sichuan earthquake?
Magnitude 8.0 earthquake 70,000 people died 400,000 people injured 5 million people made homeless up to $75 billion in damage
What were the local responses to the Sichuan earthquake?
Heavy rain, landslides and aftershocks made rescue effort very difficult
50,000 soldiers sent to help dig for survivors
Helicopters issued to help reach isolated areas
Chinese people donated $1.5 billion in aid
What were the international responses to the Sichuan earthquake?
UK gave $2 million
Finland sent 8000 tents
Indonesia sent 8 tonnes of medicine
Rescue teams flew in from Russia, Hong Kong, South Korea and Singapore
Name 5 features of an earthquake proof building in a developing country
- Cross braced wood or bamboo frame
- Concrete ring ties the walls to the foundations
- Lightweight thatch roof
- Walls made of mud and straw packed between wooden slats
- Simple steel rod foundations
What may be the cause of isolated occurrences of earthquakes (not along plate boundaries)?
- human activity
- isolated plumes of tectonic activity known as hotspots
What is liquefaction?
Loose materials e.g. soil may act like a liquid when shaken (in an earthquake). Solid rock is much safer, and buildings built on flat areas of solid rock are more resistant
What are 4 things to observe when predicting and monitoring earthquakes?
Crustal movement - small-scale movement
Changes in electrical conductivity
Strange + unusual animal behaviour (esp. carp fish)
Historic evidence - whether there are trends in the timing of earthquakes in a region
What conditions are needed for hurricanes to form ?
Sea temperatures = at least 27 degrees to a depth of 60metres
Low pressure area has to be far enough from the equator to allow the Coriolis force to create rotation in the rising mass of air
Conditions must be unstable
What is the Saffir-Simpson scale?
The Saffir-Simpson scale assigns hurricanes to 1 of 5 categories of potential disaster. The categories are based on wind intensity. Only used in Atlantic + northern Pacific