Post-earthquake Fire Spread Between Buildings Estimating And Costing Extent In Wellington

Abstract

Fires after earthquakes sometimes develop into conflagrations resulting in widespread losses of life and property. A geographic information system (GIS) model linked to property and valuation data is shown to be an appropriate tool for estimating urban fire losses. One approach uses a static buffering technique to define potential burnout zones that are sampled randomly to give estimates of losses. The other uses a dynamic cellular automaton technique for determining both the rate and extent of fire-spread in response to a wide range of factors including wind, radiation, sparking, branding, building separations and building claddings. The dynamic approach uses a set of ‘rules’ based on fire physics modified by historical data. The model runs in real time for single ignitions. The static method is used to estimate losses assuming a 12m separation will prevent fire spread All buildings are assumed combustible (upper bound case). The dynamic model assuming fire can not spread to buildings with non-combustible claddings and areas of vegetation are not flammable (lower bound case). The resulting losses are between NZ$50M and NZ$500M (excluding building contents), compared with NZ$5,000M for shaking losses for a magnitude 7.3 earthquake and a total building stock of NZ$19,000M.