managing hazards

• Prediction of earthquakes in unreliable - the best mitigation strategy is preparation. 
• Subsidence control:

  Uneven subsidence of buildings may be managed by removing water from the unsubsidised side, limiting further subsidence and levels buildings. 

   
• Frequency:

  If a quake matches building frequency it may collapse. 

  Calculating frequency of buildings shows which are at risk. 

  • F = 1/2xpie x square root of k/m 
  • F - frequency 
  • K = stiffness of building 
  • M - mass of building 

   
• Earthquake proofing buildings aims to prevent swaying, isolation from ground vibrations and to strengthen structure. 
• Sway absorbance:

  Design buildings so natural frequency does not match earthquake frequency - by using dampers and a controlled rocking frame. 

   
• Dampers are large concrete blocks mounted near building top, their inertia makes it more difficult for the building to sway. The block can be moved by springs to oppose building movement. 

   
• Rocking frames move with the energy and direct it towards fuses. Vertical tensioning pulls building back to the vertical afterwards. 
• Base isolation systems separate the vibrating ground from the building. Reducing the acceleration of the building. 

  • Rubberised blocks with lead cores are between bedrock and building 
  • Blocks deform when shaken and absorb energy 
  • Retrofitting these blocks occurs in pre-existing buildings 
• Rollers also isolate bases and move when shaken. 
• Diagonal cross bracing aids strength. 
• Lowing the centre of gravity when building using an interlocking system of triangular components. 
• Steel band strapping is cheap and involves bands being placed around buildings to prevent them falling apart. 
• Rack and pinion devices couples with a non-stick Teflon coated contact to allow smooth sliding between layers of buildings. Storeys are able to move independently of each other. 
• Wooden buildings withstand shaking better than concrete structures.