forecasting risk

• Geohazard is the probability of a change in a geological environment of a given magnitude within a specific time period in a certain area. 
• Risk is the resulting possibility of loss of life or damage to property / infrastructure. 
• Analysis:

  1. Identify risk
  2. Map 
  3. Assess
  4. Analyse 
  5. Communicate 
  6. Plan 
  7. Mitigate 
  8. Reduce 
  9. Start again 
• Hazard maps:

  Show areas most at risk from a particular hazard. May record earthquakes:

  • Epicentre of previous quake 
  • Max shaking intensity
  • Movement along faults and fault type 
  • Steep slope - landslides 
  • Infrastructure 

   
• Volcanic eruptions:

  • Infrastructure 
  • Routes of pyroclastic flows 
  • Ash thickness 
  • Valleys 
  • Wind direction 
  • Lakes 
• Hazard maps are passes on to town planners, they may ban building types, apply building regulations and plan evacuation routes. 
• Disaster plans:

  Plans that prepare for hazards and communicated through public education programmes. Immediate risk can be communicated to public by sirens, loudspeaker, TV and SMS. 

   

   
• We can Forecast an earthquake, predicting is when and where the earthquake will occur.
• Return period is the average length of time for an earthquake of a given magnitude or to happen again. Based on historical data. For example a return period of 50 years means a earthquake is likely to occur every 50 years. 
• Return period:

  T = N/n 

  N= number of years 

  n= number of events 

   
• Return period for rivers:

  T = (n+1)/m 

  T = return period 

  n = number of years held on record 

  m = rank 

   
• Probability of a return in any 1 year:

  1/T