# Relationship between severity of a hazard, its probability and degree of risk - PowerPoint PPT Presentation

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For one case study hazard analyse the relationship between severity, probability, and risk Find evidence to support this. Relationship between severity of a hazard, its probability and degree of risk . Prediction . All models built on a number of assumptions for variables:

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Relationship between severity of a hazard, its probability and degree of risk

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#### Presentation Transcript

For one case study hazard analyse the relationship between severity, probability, and risk

Find evidence to support this

Relationship between severity of a hazard, its probability and degree of risk

### Prediction

• All models built on a number of assumptions for variables:

What would they be for earthquake?

• Tohoku – prediction of 99% probability that earthquake 7.5 would occur in next 75 yrs

• Defences built around this

• Models of plate tectonics assumed that there would not be simultaneous slips in faults

• Several incorrect assumptions based on historical observations

### Why do hazard maps matter?

• Deciding how much of a country’s resources should be spent on mitigation

• Building tsunami defences large enough to withstand the 2011 event is too expensive

• Those built were able to withstand tsunamis experienced every 200-300 yrs

### Cost vs mitigation

Total cost of event / losses / defences

Extent to which losses can be minimised

(mitigation)

A hazard model is crucial because it is used to predict the probabilities of tsunamis of different heights and hence the expected loss

### Unzipping theory

• http://www.bbc.com/future/story/20120920-will-we-ever-predict-earthquakes

### How can EQ’s be predicted? Write notes on 2 methods used…

• http://science.howstuffworks.com/nature/natural-disasters/earthquake7.htm

• http://www.livescience.com/6935-method-promises-earthquake-prediction.html

### For your MEDC and LEDC EQ Case Studies…

• Had the earthquake been predicted?

• What degree of prediction had been given?

• What actions [if any] had been taken due to the predictions?

### Hurricanes

What are the methods used to predict hurricanes? (time, magnitude and location)

How is this communicated to the public?

What factors will affect predictions of the potential impacts?

What are the limitations to these methods?