Understanding time variation of risk

Information about temporal variations in risk, attributable to changes in the human component of natural disasters, is rarely included in disaster assessments carried out by hazard management professionals. Whereas the risk of extreme natural events will probably remain unchanged during the lifetimes of today's population, the probability of large urban disasters appears to be increasing rapidly. Recent earthquakes in Northridge (1994) and Kobe (1995) are indicators of these trends. This paper introduces an integrated approach to urban risk assessment that focuses on the changing risk and vulnerabilities of large cities to earthquakes. These cities can be thought of as complex socio-technical systems, comprising interdependent subsystems that may be modelled econometrically. The construction of one such model is discussed, as well as the procedure for simulating changes in case-study urban areas over different time periods, with and without the occurrence of major earthquakes. Implications of the model for hazard management are identified.